Oct 22, 2015 - The top of the atmosphere has an air mass density equal to zero (AMD0) .... mixture of CH3NH3I and PbI2 in g-butyrolactone solution (perovskite precursor ..... film, thus determining the open circuit voltage (Voc) of the device. An addition ... only two minutes and a low processing temperature are sufficient to.
Republic of Iraq Ministry of Higher Education and Scientific Research University of Baghdad College of Science
Fabrication and Characterization of Perovskite Solar Cells A Thesis Submitted to the council of College of Science University of Baghdad In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in Physics
By
Aqel Mashot Jafar (B.Sc. In Physics 2000) (M.Sc. In Physics 2009)
Supervised by Professor . Dr. Mahdi Hasan Suhail
1438H
2017
بسم اهلل الرمحن الرحيم
﴿ قالوا سبحانك الَ علم لنا إال ما علمتنا انك أنت العليم احلكيم ﴾ صدق اهلل العلي العظيم.
سورة البقرة اآلية ( ) ۲۳
Dedication To my Homeland & my sons
I Acknowledgments First and foremost , I would like to thank my god for protecting me and giving me faith and strong to complete my research . I hope that this work is under the acceptance of Allah.. It is impossible to do justice to all the great people from whom I received help and support in various ways throughout my research in only few lines. Nevertheless, I will try to make an attempt to express my gratitude: With my pleasure to end my project, I would like to express my deep appreciation and indebtedness to my supervisor Dr. Mahdi Hasan Suhail for the interesting research topic ,continuous advice and him guidance throughout this work . I am grateful to the Dean of the college of sciences and the chairman of physics department for their help. My thanks are extended to the staff of solar energy research center , especially , Director of center , Dr. Falah Mustafa Al-Attar for guidance throughout this work and their help . My thanks are extended to the staff of hydrogen and bio-fuel department , especially , Head of department Kiffah Al-Amara for their help . My thanks are extended to the staff of plasma department , especially , Head of department , Dr . Mohammd K. Kalaf for their help . Thanks also to all the staff of Physics Department, for giving me this opportunity to continue my study . Finally, I want to thank my family: My father , who always supported and encouraged me in pursuing a scientific career and of course my beloved (my wife) and my sons for loving them . Aqel
П Abstract : In this research , the aim is clean energy generated of peroveskite solar cells with low cost. Organolead halide Perovskite Solar Cells (OPSC) which employed CuI as Hole Transport Layer (HTL) are fabricated .Optical and structural properties of sensitized absorption layer CH3NH3PbX3, X= I, Br, Cl or mix of these halide, that Photovoltaic devices are studied . XRD patterns of CH3NH3PbX3 compounds are indicated to be tetragonal and cubic structure at X = I or Br, tetragonal structure at X is mixed of I and Cl and cubic structure at X is mixed of Br and Cl . The best Power Conversion Efficiency (PCE) of OPSC is (2.15) to the device have CH3NH3PbI3 as sensitized absorption layer. Measurements are tested at AM1.5 global sunlight (100 mW cm−2). Organolead iodide Inorganic Perovskite Solar Cells (OIPSC) which employed CsPbIxBryCl3-(x+y)
as
a Hole Transport Layer have been
fabricated in the laboratory . XRD patterns of
CsPbIxBryCl3-(x+y)
compounds were indicated to be cubic Perovskite Structure at (x = 0, y = 0, 2) and the hexagonal structure at (x = 1, y = 0,1,2 ). The best (PCE) of OIPSCs were (1.45% or 0.81%) to the cubic or hexagonal structure of HTL (CsPbCl3 or CsIPbBr2) devises, respectively.
All
measurements are tested at AM1.5 global sunlight (100 mW cm−2). Free-Lead halide Perovskite Solar Cells (FLPSC) which employed anhydrous SnCl2
in place of
PbX2
for synthesis peroveskite
composites as sensitized absorption layer, harvesting light of devices, are fabricated . FLPSCs, comparative of OPSCs and OIPSCs, give the lowest
efficiency . The best PCE to FLPSCs is (PCE = 0.05%).
Measurements are tested at AM 1.5 global sunlight (100 mW cm−2).
The surface morphology of the thin films of all samples have been observed by using Atomic Force Microscope (AFM) or Scanning Electron
Microscope
(SEM).
The
investigation of perovskite materials
crystal
graphic
orientations
were analysis by XRD . The
optical properties of peroveskite thin films of all solar cells are studied by UV/Vis spectrophotometer . The I-V measurement solar cell test reports of all devices were studied by Integrated cell tester included I-V Photovoltaic measurements system and Solar simulator system.
III NOMENCLATURE Symbol
Definition
OPSCs
Organolead halide Perovskite Solar Cells
OIPSCs
Organolead iodide Inorganic Perovskite Solar Cells
FLPSCs
Free-Lead halide Perovskite Solar Cells
PCE
Power Conversion Efficiency
XRD
X-Ray Diffractions
HTM
Hale Transport Materials
HTL
Hale Transport Layers
AM1.5
Air Mass radiation at the surface of Earth
AFM
Atomic Force Microscope
SEM
Scanning Electron Microscope
AMD0 PSC MAPbI3
Air Mass radiation at the top of the atmosphere Perovskite Solar Cells Methyl-Ammonium Lead Iodide (CH3NH3PbI3)
ITO
Indium Tin Oxide
FTO
Fluorine doped Tin Oxide
GBL
G-ButyroLactone
DMF
N,N-Di Methyl Formamide
spiro-OMeTAD
2,2′,7,7′-tetrkis-(N,N-di-p-methoxyphenyl-amine)-9,9′-spirobifluorine
MAPbBr3
Methyl Ammonium Lead Bromide (CH3NH3PbBr3)
PQDSC
Perovskite Quantum-Dot-sensitized Solar Cell
EAPbI3
Ethyl-Amine Iodide with Lead Iodide (CH3CH2NH3)PbI3
DSSC
Dye Sensitize Solar Cell
N719
(cis‐diisothiocyanato‐bis(2,2′‐bipyridyl‐4,4′‐dicaboxylato) ruthenium(II) bis‐(tetrabutylammonium))
NRTiO2 CE IPCE (FAPbIyBr3-y)
Nano-Rod TiO2 Counter Electrode Incident Photon to Current Efficiency Formamidinium Lead trihalide perovskites
NOMENCLATURE Symbol PCBM (M-)TiO2 HJ
Definition [6,6]-Phenyl C61-Butyric acid Methyl ester Mesoporous TiO2 Hetero-Junction
PEDOT:PSS
Poly(3,4-EthyleneDiOxyThiophene) Poly-Styrene Sulfonate
PFN
Poly[(9,9-bis(30-(N,N-dimethylamino) propyl)-2,7-Fluorene)alt-2,7-(9,9-dioctylfluorene
TCA
Transparent Conducting contact Adhesive
MSSC
Meso-Super-structured Solar Cell
Li-TFSI
Lithium-bis(TriFl uoromethaneSulfonyl) Imide
MAI
Methyl-Amine Iodide (CH3NH3I3)
CNT
Carbon Nano-Tube
SC-FB
short circuit to forward bias
FB-SC
Forward bias to short circuit
AACVD
Aerosol Assisted Chemical Vapor Deposition
SC
Spin Coating
TE
Thermal Evaporation
DCSD
DC Sputtering Deposition
TED
Thermal Evaporation Deposition
OPM
Organic Perovskite Materials
IPM
Inorganic Perovskite Material
IV CONTENTS Acknowledgments
I
Abstract
П
Nomenclature
III
Contents
IV
Chapter one : Introduction and Literature Review
1 2
Introduction Device architectures Literature Review
5 6 17
The aim of the project Chapter two : Theory of perovskite materials
18
2.1Introduction
19
2.2Theory of perovskite materials
19
2.2.1 Photo anodes
21
2.2.2 Hale Transport Material (HTM)
24
2.2.3 Manufacturing and possesses
25
2.2.4 Charge transfer mechanisms
27 29
2.3 Challenges 2.3.1 Stability
29
2.3.2 Toxicity
31
2.3.3 Hysteresis effect
31
2.4 Basic Terms for Photovoltaic Performance
33
2.5 Structures of perovskite materials
35
2.5.1 Tolerance factor and transformation
37
phase of perovskite materials 2.5.2 X-ray diffraction of perovskite materials
42
2.6 Optical properties of perovskite materials
48
2.7 Electric properties of perovskite materials
51
2.8 Electronic properties of perovskite materials
53
Chapter three : The Experimental work
55
3.1Introduction
56
3.2Characterization Techniques
56
3.2.1 Structural studies X-Ray Diffraction (XRD)
56
3.2.2 Morphological studies
57
3.2.2.1 Atomic Force Microscope (AFM)
57
3.2.2.2 Scanning Electron Microscope (SEM)
58
3.2.3 Optical properties studies
59
3.2.4 I-V and Parameters Characteristics of OPSCs
59
studies 3.3 Deposition processes Techniques 3.3.1 Aerosol Assisted Chemical Vapor Deposition
62 62
technique (AACVD) 3.3.2 Spin Coating technique (SC)
63
3.3.3DC Sputtering Deposition (DCSD)
64
3.3.4Thermal Evaporation Deposition (TED)
66
3.4 Fabrication of Organic Perovskite Solar Cells
67
(OPSCs) devices 3.4.1Introduction 3.4.2 Synthesis of Organic Perovskite Materials
67 69
(OPM) 3.4.3 cleaned the substrates
70
3.4.4Fabrication of (OPSCs) devices
71
3.5 Fabrication of Organic –Inorganic Perovskite Solar
73
Cells (OIPSCs) devices
3.5.1 Introduction
73
3.5.2 Fabrication processes of solar cells devices
74
3.6 Fabrication of Free Lead halide Peroveskite Solar
76
Cells (FLPSC) Chapter four : Results and Discussions
78
4.1 Introduction
79
4.2 Results and Discussions of OPSCs
79
4.2.1 Structure properties
79
4.2.2 Optical properties
85
4.2.3Parameters of OPSCs
88
4.2.4 Energy Band diagram of the Methyl-amine
93
Lead Iodide PSC 4.2.5 Summary of results of OPSCs 4.3 Results and Discussions of (OIPSCs) devices
95 96
4.3.1 Structure properties
96
4.3.2 Optical properties of inorganic HTM
101
4.3.3Parameters of OIPSCs
103
4.3.4 Summary of results of OIPSCs
106
4.4 Results and Discussions of Free Lead halide
108
Peroveskite Solar Cells (FLPSCs) 4.4.1 Stricture properties of peroveskite materials
108
4.4.2 Optical properties of peroviskite materials
110
4.4.3 Parameters of FLPSCs
112
4.4.4 Summary of results
113
of FLPSCs
Chapter five : The Conclusions and Suggestions
114
5.1 General Conclusions
115
5.2 Suggestions for Future Work
118
References
119
Intruduction
Chapter one
Literature Review
Aim of project
1.1 Introduction Global energy consumption has been continually increasing with population growth and fast-paced industrial development
in recent
decades, which demands renewable energy sources in view of long-term sustainable development. Generating cost-effective and environmentally benign renewable energy
remains a major challenge for both
technological and scientific
development. Solar cells based on the
photovoltaic with the advantages of decentralization and sustainability have attracted great attention in the past 50 years. Currently, the photovoltaic markets is dominated by crystalline silicon-based solar cells with a share of 89% ; however, a cost-effective and highthroughput material named perovskite has proven to be capable of Power Conversion Efficiency (PCE) 15.9%, compared to 3.8% of PCE that was obtained only four years ago[1]. At generally, solar cells use photons from the solar spectrum and convert those photons into
electricity. The incident photons have
various wavelengths (λ) and energy of photons is depending upon the wavelength, that an energy can be expressed in units of electron volts (eV). The amount of energy available from the sun’s irradiance has been modeled as having a ~5760 K blackbody spectrum at the top of the atmosphere. The top of the atmosphere has an air mass density equal to zero (AMD0), whereas the surface of Earth has an AMD = 1.5 (AMD1.5) due to the constituent elements of the atmosphere and the gravitational field. The total energy from the sun’s irradiance at the Earth’s surface is 932 – 965 W/m2, which has been normalized to 1000 W/m2 for ease of application. Figure 1.1 illustrates wavelength distribution of the solar spectrum [2].
Fig1.1:Solar Energy Distribution Intensity vs. Wavelength at AMD1.5[2]
In the present decade, organic–inorganic halide perovskite solar cells have been the most significant development in the field of photovoltaic's and are the best bet at satisfying the need for high efficiencies while allowing for low cost solution based manufacturing. Low cost, stability and high efficiency are research reason in the development of organicinorganic perovskite solar cells. Organolead halide perovskite solar cells has attracted researchers attention as a light harvester for perovskite solar cells because of its tenable band gap, large absorption coefficient, high charge carrier mobility, and long electron−hole diffusion[3]. High voltage is a sign of minimized thermal loss in the charge transfer across solid-solid hetero-junctions which normally undergoes a barrier loss of >0.2 eV per junction. Further advancement of the perovskite photovoltaic caused by expanding the spectral sensitivity to over 900 nm and preparation ease of organolead halide perovskite materials at room temperatures[4]. Recently, the performance of Perovskite Solar Cells (PSC) has attracted intensive attention and studies. Foresee ably, many
transformative steps will be put forward over the coming few years to OPSC , as shown in figure 1.2 , comparative to other solar cells systems .
Fig. 1.2. Efficiency evolution of different thin-film photovoltaic technologies [1].
Within a short period from August 2012 to December 2013, the PCE of perovskite-based solar cells was significantly improved from 7.2% to 15.9%, the high PCE of these systems are
associated with the
comparable optical absorption length and charge-carrier diffusion lengths, transcending the traditional constraints of solution-processed semiconductors and out-performing most other third-generation thinfilm solar cell technologies that have been studied for decades, as shown in the Figure1.2 [1]. Progress in PSC comparative Dye-Sensitized Solar Cells (DSSCs),A PCE of less than 1% was first reported in 1998 of DSSC using spiro-MeOTAD in combination with N719. A change from N719 to organic dye D102 enhanced the PCE to 4% in 2005[5].
1.2 Device architectures: A common device configuration for Methyl-Ammonium Lead Iodide (MAPbI3) with chemical formula
CH3NH3PbI3 based solar
cells
consists of in filtrating the perovskite with scaffold an n-type mesoporous layer [6,7], Nano-Rod [8,9] and without scaffold or planar layer [10] as shown in figure 1.3.
Fig. 1.3. Architecture schematics of three types of OPSC: (a) mesoporous TiO2∕Al2O3∕ZrO2[6,7], (b) TiO2∕ZnO NRs [8,9], and (c) without the scaffold layer[10]. The solar cell fabrication process commences with the deposition of a compact TiO2 hole-blocking layer on top of the fluorine doped tin oxide (FTO) or Indium Tin Oxide (ITO) substrate. This is typically done through the spray pyrolysis of precursors diisopropoxidebis
(acetylacetonate)
upon
such as titanium preheated
transparent
conductive glass such as FTO or ITO at 450 0C [9]. It is important to ensure that the compact layer is pinhole-free and uniform to prevent the recombination between carriers from the perovskite layers and FTO. On top of the compact layer, a meso-porous layer of n-type TiO2 is formed either by screen printing or spin coating a nano-particle TiO2 precursor solution followed by annealing to remove the polymeric binders [11] . The
thickness and porosity of these layers can be modulated by
changing the filler and solvent concentrations in the TiO2 precursor solution .The perovskite films are then deposited on top of the n-type meso-porous layer by spin coating of precursor solution of perovskite
prepared materials
with a suitable solvent such as g-butyrolactone
(GBL) or N,N-dimethylformamide (DMF) and annealing at 150 0C [1215]. This is followed by the deposition of a hole transporting material (HTM) such as spiro-OMeTAD with appropriate dopants to improve conductivity [12]. Finally, a metal electrode is deposited on top of the HTM to complete the solar cell as shown in figure (1-3). Table (1-1) summarized review of PSCs in previous studies . 1.3 Literature Review: This review focuses on the recent developments in perovskite solar cells as well as their device architectures. We first review the photoanodes, perovskite thin films and hole transport materials of the class of device architectures of perovskites solar cells. An addition, preparation methods of perovskite materials is discussed in the literatures survey, as shown in table (1.1). Due to the rapid pace of research in this area, this review does not aim to be comprehensive but will highlight key studies and
findings. In addition , we are summarized the parameters of
photovoltaic devices in the table (1.1) and detailed studies are exhibited in these review.
Table (1.1) summarized review of PSCs in previous studies . Perovskite
Photo-anode
materials
Deposition
HTM
method
Area
PCE
Ref and
(cm)2
%
Year
MAPbI3/MApbBr3
TiO2
Dropping
I-/I3-
0.38
3.81
2009[1,13]
MAPbI3
TiO2
Spin coating
I-/I3-
0.303
6.54
2011[14]
MAPbI3
TiO2
Spin coating
No
0.12
5.5
2012[15]
EAPbI3
TiO2
Spin coating
I-/I3-
0.323
2.4
2012[16]
CsSnI3 + N719
TiO2
injected
CsSnI2.95F0.05
0.2
10.2
2012[17]
MAPbI3
NR-TiO2
Spin coating
spiro-MeOTAD
0.215
9.4
2013[9]
MAPbI3
TiO2
full printable
C
0.5
6.64
2013[18]
MAPbI3
TiO2
Spin coating
Spiro-MeOTAD
2
2013[19]
FAPbI3
TiO2
Spin coating
Spiro-MeOTAD
14.2
2014[20]
MAPbI3
TiO2
Spin coating
MAPbInBr3−n
0.09
8.54
2014[21]
MAPbI3
PC61BM
Spin coating
NiO
0.06
9.51
2014[22]
MAPbI3
TiO2
Spin coating
CuI
0.09
6.0
2014[23]
MAPbI3
M-TiO2
Spin coating
C
0.06
9
2014[24]
MAPbI3-xClx
PEDOT:PSS
Spin coating
PCBM/PFN
0.1
17.1
2014[25]
MAPbI3-xClx
TiO2/Al2O3
Spin coating
Spiro-MeOTAD
0.062
13.3
2014[26]
MASnI3–xBrx
TiO2
spin coating
Spiro-MeOTAD
0.1
5.73
2014[27]
MAPbInBr3−n
TiO2
spin coating
MAPbInBr3−n
0.09
8.54
2014[29]
MAPbI3
CuInS2/Al2O3
spin coating
No
0.04
5.3
2014[30]
MAPbI3
ZnO
spin coating
Spiro-MeOTAD
11
2015[31]
TiO2/ZrO
spin coating
Spiro-MeOTAD
15.8
2015[32]
MAPbI3/ MAPbCl3
0.1
In 2009 , the first perovskite-sensitized TiO2 solar cell used liquid electrolytes
with dropping deposition based on Methyl Ammonium
Lead Iodide (MAPbI3 ) and Methyl Ammonium Lead Bromide (MAPbBr3 ) as absorption layers of devices
. The corresponding
devices gave PCEs of 3.8% and 3.1%, respectively [1,13], as shown in the table (1-1). After two years , a conversion efficiency of 6.54%
at one sun
illumination is reported by Park’s group based on Perovskite QuantumDot-sensitized Solar Cell(PQDSC). Spin coating
of the equimolar
mixture of CH3NH3I and PbI2 in g-butyrolactone solution (perovskite precursor solution) leads to
(CH3NH3)PbI3 quantum dots (QDs) on
nanocrystalline TiO2 surface. Jeong-Hyeok et al Studied on TiO2 film thickness effect and illustrated that thinner TiO2 film thickness have higher photocurrent density compared to relatively thicker layer due to high absorption coefficient of PQDSC, however, that the stability of the perovskite (CH3NH3)PbI3 QD-sensitized solar cell under continued irradiation is approximately 10 min (about 80% degradation) due to QD tends
to be
dissolved
gradually into the
redox
liquid
electrolyte (I-/I3-) [14]. In 2012, Lioz Etgar et al are reported for the first time on a hole conductor-free
mesoscopic
Methyl-Ammonium
lead
iodide
(CH3NH3PbI3) perovskite/TiO2 hetero-junction solar cell, produced by deposition of perovskite nanoparticles from a solution of CH3NH3I and PbI2 in γ-butyrolactone by the spin-coating technique on a 400 nm thick film of TiO2 (anatase) nano-sheets exposing (001) facets . A gold film was evaporated on top of the CH3NH3PbI3 as a back contact. Importantly, the CH3NH3PbI3 nanoparticles assume here simultaneously the roles of both light harvester and hole conductor, rendering superfluous the use of an additional hole transporting material. The simple mesoscopic CH3NH3PbI3/TiO2 hetero-junction solar cell shows impressive photovoltaic performance, with short-circuit photocurrent Jsc= 16.1 mA/cm2, open-circuit photovoltage Voc = 0.631 V, and a fill factor FF = 0.57, corresponding to a (PCE) of 5.5% under standard AM 1.5 solar light of 1000 W/m2 intensity. At a lower light intensity of 100W/m2, a PCE of 7.3% was measured[15]. In the same year, Jeong-Hyeok Im et al were synthesized a new nanocrystalline Ethyl-Ammonium Lead Iodide (EAPbI3) with the chemical formula (CH3CH2NH3)PbI3 by reacting Ethyl-Amine Iodide
with Lead Iodide, and its crystal structure is investigated and confirmed orthorhombic crystal phase. The valence band position at 5.6 eV versus vacuum and the optical bandgap of 2.2 eV are determined . A spin coating of the CH3CH2NH3I and PbI2 mixed solution on a TiO2 film is yielded
1.8nm diameter (CH3CH2NH3)PbI3 dots on the TiO2 surface.
The (CH3CH2NH3)PbI3-sensitized solar cell with iodide-based red-ox (I/I3-) electrolyte demonstrates the conversion efficiency of 2.4% under AM 1.5 G one sun (100 mW/cm2) illumination [16] . Also , In Chung et al were reported that the solution p-type direct band gap semiconductor
CsSnI3 can be
used for hole conduction
instead of a liquid electrolyte in Dye Sensitize Solar Cell (DSSC) . As consequence ,
solid-state dye-sensitized solar cells consisted of
CsSnI2.95F0.05 doped with SnF2 , nanoporous TiO2 and the dye N719, were shown conversion efficiencies up to 10.2 % with a band gap of 1.3 eV . CsSnI3 enhanced visible light absorption on the red side of the spectrum to perform the typical dye-sensitized solar cells in this spectral region[17]. In 2013, Hui-Seon Kim et al are reported a highly efficient solar cell based on a submicrometer (0.6 μm) rutile TiO2 Nano-Rod (NRTiO2) sensitized with MAPbI3 perovskite nanodots. Rutile nanorods were grown hydrothermally and their lengths were varied through the control of the reaction time. Infiltration of
spiro-MeOTAD hole transport
material into the perovskite-sensitized nanorod films
demonstrated
photocurrent density of 15.6 mA/cm2, voltage of 955 mV, and fill factor of 0.63, leading to a power conversion efficiency (PCE) of 9.4% under the simulated AM 1.5G one sun illumination. Photovoltaic performance was significantly dependent on the length of the nanorods, where both photocurrent and voltage decreased with increasing nanorod lengths [9].
In the same year , Zhiliang Ku et al were developed a mesoscopic Methyl-Ammonium Lead Iodide (MAPbI3) perovskite/TiO2 heterojunction solar cell with low-cost carbon counter electrode (CE) via full printable process. With carbon black/ spheroid graphite CE, this mesoscopic hetero-junction solar cell presents high stability and power conversion efficiency of 6.64%, which is higher than that of the flaky graphite based device and comparable to the Au electrode [18] . Also, Saman Ghanavi was reported that the perovskites materials MAPbI3 and MASnI3 are used as both light absorbing material and hole conducting material (HTM) . Both perovskites were manufactured by mixing Methyl Ammonium Iodide with either Lead Iodide or Tin Iodide in different concentrations. This was then deposited on a 600nm thick mesoporous TiO2 layer. Deposition of the hole-transporting material (HTM) was done by spin-coating spiro-OMeTAD. Lastly thermal evaporation was used to deposit a silver electrode. The Lead perovskite solar cell device was subjected to illumination with Air Mass 1.5 sunlight (100mW/cm2) which produced an open circuit voltage Voc of 0.645 V, a short circuit photocurrent Jsc of about 7 mA/cm2, and a fill factor FF of 0.445. This resulted in a power conversion efficiency (PCE) of about 2% and an incident photon to current efficiency (IPCE) of up to 60%. The Tin perovskite solar cell device was shown low performance using the same device construction as for the
Lead
perovskite. However, the incident photon to electron conversion affirms that there is a current in the visible region, and IPCE of 12.5 % was observed at 375nm[19] . Around 2014 , Eperon et al were showed the effect of replacing the Methyl-Ammonium cation in this perovskite, with the slightly larger Formamidinium
cation. They synthesized Formamidinium Lead
trihalide perovskites (FAPbIyBr3-y) , with y increasing from 0 to 1 ,
FAPbIyBr3-y
have a band-gap tunable
between 1.48 and 2.23 eV,
respectively . They took the 1.48 eV-band-gap perovskite as most suited for single junction solar cells, and demonstrated long-range electron and hole diffusion lengths in this material, making it suitable for planar heterojunction solar cells. they fabricated such devices, and due to the reduced band-gap they achieved high short-circuit currents of >23 mA cm-2, resulting in power conversion efficiencies of up to 14.2%, the highest efficiency yet for solution processed planar heterojunction perovskite solar cells. Formamidinium lead triiodide was
hence
promising as another candidate for this class of solar cell [20] . Sigalit
Aharon
et
al
(2014)
were
reported
that
used
CH3NH3PbInBr3−n (where 0 ≤ n ≤ 3) as hole conductor and
light
harvester in the solar cell. Various concentrations of methylammonium iodide and methylammonium bromide were studied which reveal that any composition of the hybrid CH3NH3PbInBr3−n can conduct holes. The hybrid perovskite was deposited in two steps, separating it to two precursors to allow better control of the perovskite composition and efficient tuning of its band gap . The hybrid iodide/bromide perovskite hole conductor free solar cells showed very good stability, their power conversion efficiency achieved 8.54% under 1 sun illumination with current density of 16.2 mA/cm2. The results of this work open the possibility for graded structure of perovskite solar cells without the need for hole conductor [21]. Also, Kuo-Chin Wang et al (2014) presented a new paradigm for organo-metallic hybrid perovskite solar cell using NiO inorganic metal oxide nano-crystalline as p-type electrode material and realized the first mesoscopic NiO/perovskite/[6,6]-Phenyl C61-Butyric acid Methyl ester (PCBM) hetero-junction photovoltaic device. The photo-induced transient absorption spectroscopy results verified that the architecture is
an effective p-type sensitized junction, which is the first inorganic ptype, metal oxide contact material for perovskite-based solar cell. Power conversion efficiency of 9.51% was achieved under AM 1.5 G illumination, which significantly surpassed the reported conventional ptype dye-sensitized solar cells. The replacement of the organic hole transport materials by a p-type metal oxide has the advantages to provide robust device architecture for
further development of all-inorganic
perovskite-based thin-film solar cells [22]. Also, Christians et al (2014) reported the new inorganic hole conducting materials for the perovskite based thin film photovoltaics , they have identified copper iodide (CuI) as a possible alternative. Using copper iodide, they have succeeded in achieving a promising power conversion efficiency of 6.0% with excellent photocurrent stability. The open-circuit voltage, compared to the best spiro-OMeTAD devices, remains low and is attributed to higher recombination in CuI devices as determined
by
impedance
spectroscopy.
However,
impedance
spectroscopy revealed that CuI exhibits two orders of magnitude higher electrical
conductivity
than
spiro-OMeTAD
which
allows
for
significantly higher fill factors. Reducing the recombination in these devices could render CuI as a cost effective competitor to spiroOMeTAD in perovskite solar cells [23]. Also , Huawei Zhou et al (2014) reported that successfully prepared full solution processed
low-cost TiO2/MAPbI3 hetero-junction (HJ)
solar cells based on a low
temperature
carbon electrode. Power
conversion efficiency of Mesoporous (M-)TiO2/MAPbI3/C HJ solar cells based on a low-temperature-processed carbon electrode achieved 9%. The devices of M-TiO2/MAPbI3/C HJ solar cells without encapsulation exhibited advantageous stability (over 2000 h) in air in the dark. MAPbI3 was deposited by two-step sequential deposition . Two-step
methods afford higher loading of Lead Iodide by first spin coating of lead iodide followed by
solution processing or vacuum assisted
deposition of MAI . The ability to process low-cost carbon electrodes at low temperature on top of the MAPbI3 layer without destroying its structure
reduces the cost and simplifies the fabrication process of
perovskite HJ solar cells. This ability also provides higher flexibility to choose and optimize the device [24] . Also , Jingbi You et al (2014) reported a growth mode for via thermal
annealing of the perovskite precursor film in a humid
environment (e.g., ambient air) to greatly improve the film quality, grain size, carrier mobility, and lifetime. The details of device fabrication were included : Specifically, the mixture solution of 1:3 ratio of PbCl2:MAI in N,N-DiMethylFormamide (DMF) solvent (0.8M) was spin coated onto the Poly(3,4-EthyleneDiOxyThiophene)
Poly-
Styrene Sulfonate (PEDOT:PSS) . The precursor film are annealing at 90 C for 2 h in nitrogen glove box or dry oxygen glove box or ambient air (humidity of 35% ± 5%) . Following by , 2% of (PCBM) in chlorobenzene solution was coated onto the perovskite layer . After that, 0.02% polyelectrolyte Poly[(9,9-bis(30-(N,N-dimethylamino) propyl)2,7-Fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN) in methanol was spincoated on PCBM. Finally, the device was transferred to vacuum chamber for Al electrode evaporation to obtain devices consisting of (glass/ITO/PEDOT:PSS/MAI3-xClx/PCBM/PFN/Al) . The
mentioned
method produces devices with maximum power conversion efficiency of 17.1% and a fill factor of 80%, revealing a promising route to achieve high quality perovskite polycrystalline films with superior optoelectronic properties that can pave the way towards efficient photovoltaic conversion [25] .
In the course of 2014, Daniel Bryant et al developed a novel semitransparent electrode design combining a polymer embedded nickel grid with a Transparent Conducting contact Adhesive (TCA) that can be applied to
perovskite based devices providing conductivity, charge
extraction, mechanical adhesion and protection. This has allowed indium-tin oxide (ITO), Au and Ag free entirely non-vacuum processed PSC devices to be fabricated with a solar-to-electrical power conversion efficiency (PCE) of over 13.3% . The data presented in this initial study has shown that the TCA-contact is a simple low cost alternative to a gold evaporated contact[26]. Also, Feng Hao et al (2014) reported that methylammonium tin halide perovskites (MASnI3-xBrx) have been used as lead-free light harvesters for solar cell applications . Featuring an ideal optical bandgap of 1.3 eV, devices with MASnI3 perovskite together with an organic spiro-OMeTAD hole-transport layer showed a notable absorption onset up to 950 nm, which is significantly redshifted compared with its benchmark MAPbI3 counterpart (1.55 eV). The bandgap engineering of MASnI3-xBrx perovskites can be controllably tuned to cover much of the visible spectrum, thus enabling the realization of lead-free, colourful solar cells and leading to a promising initial PCE of 5.73% under simulated full sunlight. Further efficiency enhancements would be expected by the fundamental understanding of the internal electron dynamics and corresponding interfacial
engineering. The reported
MASnI3-xBrx perovskites are believed to represent a significant step towards the realization of low-cost , high-efficiency, environmentally benign , next-generation solid-state solar cells. [27]. Also ,Belen Suarez et al (2014) reported that the insertion of both Cl and Br in the perovskite lattice of MAPbI3 of perovskite solar cell devices reduces the charge recombination rates in the light absorber
film, thus determining the open circuit voltage (Voc) of the device. An addition ,the samples prepared on a mesoporous Al2O3 electrode present lower charge recombination rates than those devices prepared on mesoporous TiO2. Furthermore, the addition of Br in the perovskite structure was demonstrated to improve slightly the lifetime of the devices; in fact, the efficiencies of all devices tested remained at least at the 80% of the initial value 1 month after their preparation. These results highlight the crucial role of the charge-recombination processes on the performance of the perovskite solar cells and pave the way for further progress on this field [28]. Sigalit Aharon et al (2014) were presented used the MAPbInBr3−n, (at 0 ≤ n ≤ 3) as hole conductor and light harvester at (n = 3) in the Perovskite solar cell. The hybrid iodide/bromide perovskite hole conductor free solar cells show very good stability, their PCE achieved 8.54% under 1 sun illumination with current density of 16.2 mA/cm2. The results of this work open the possibility for graded structure of perovskite solar cells without the need for hole conductor[29] . Also, Chong Chen et al (2014) reported that the solution-processed MAPbI3 perovskite/copper indium disulfide (CuInS2) planar heterojunction solar cells with Al2O3 as a scaffold were successfully fabricated at a temperature as low as 250°C for the first time, in which the indium tin oxide (ITO)-coated glass instead of the fluorine-doped tin oxide (FTO)-coated glass was used as the light-incidence electrode and the solution-processed CuInS2 layer was prepared to replace the commonly used TiO2 layer in previously reported perovskite-based solar cells. The ITO/CuInS2/Al2O3/MAPbI3/Ag cell showed the best performance and achieved PCE up to 5.30% [30]. During 2015 , Jie Zhang et al
describe a fast, simple and low
temperature electrochemical technique for the preparation of zinc oxide
layers on rigid and flexible substrates. The layers, prepared from a zinc nitrate precursor, are of high structural and optical quality. They have been optimized to be applied as efficient electron transport layers in MAPbI3-sensitized perovskite solar cells (PSCs) with Spiro-MeOTAD as hole transport layers. They show that an electro-deposition time of only two minutes and a low processing temperature are sufficient to fabricate solar cells with a power conversion efficiency close to 11% . For a longer deposition time, the efficiency decreases due to a slight reduction in Jsc and Voc [31]. In the same year, Hsin-Hua Wang et al developed a facile and quantitative method to improve the electron transport properties and resulting device performances of perovskite solar cells based on postincorporation of various acetylacetonate additives. Previous studies rely on synthesis or soaking processes with limited additive control. Here, acetylacetonated based additives are used as effective intermediate gels to interact with TiO2 nanocrystals using a simple approach. The incorporation process can be controlled effectively and quantitatively using a range of
additives from divalent (II), trivalent (III), and
tetravalent (IV) to hexavalent (VI) acetylacetonate. Zirconium(IV) acetylacetonate was found to be the most effective additive, with average PCE improved from 15.0% to 15.8% [32].
1.4 The aim of the project: The aim of this project is included to fabricate Organic Inorganic Perovskite Solar Cells (OIPSCs), Organic Perovskite Solar Cells (OPSCs) and Free Lead Perovskite Solar Cells (FLPSCs) from the available initial materials via employing easy and obtainable methods to manufacturing the samples as spin coating ,thermal evaporation , spray pyrolysis and DC-Sputtering Deposition Techniques and to study all parameters of fabrication and testing of devices . OIPSCs are employed Methyl Ammonium Lead Iodide (MAPbI3) as absorption layer, harvester light materials, and Cesium Lead Halide ,CsPbX3 (X= I, Br, Cl or mix of them ), as hole transport materials. These materials are considered available initial materials, obtained it of simple preparation methods in comparison to the previous studies which implying spiro-OMeTAD as expensive hole transport materials. OPSCs are employed Methyl Ammonium Lead Halide MAPbX3 (X= I, Br, Cl or mix of them ), as absorption layer, harvester light materials, and copper Iodide as hole transport materials. These materials have simple preparation methods or available materials in commercial markets. FLPSCs are employed Methyl Ammonium Tin Halide MASnX3 (X= I, Br, Cl or mix of them ), as absorption layer, harvester light materials, and copper Iodide as hole transport materials. These materials are considered available materials and friendly environment, composites without Lead to avoid risks of composites Lead.
Chapter Two
Theory of perovskite materials
Structural , Optical , Electrical and Electronical properties of perovskite materials
2.1 Introduction : This theory part, at first , focuses on the basic terms for photovoltaic devices followed by its focuses on the recent studies in perovskite materials of solar cells as well as their structural, optical, electrical, electronic and
photo-physical
properties. The following review
discussed the structural properties of the transformation phase of the organic-inorganic perovskites materials class and confirmed with plots of
X-Ray Diffraction (XRD).Optical energy gap correlated with
structural phase of perovskite materials and absorption coefficient of perovskite thin films are explicated by the optical properties .The orientational polarizability and the dielectric permittivity of organic– inorganic perovskites are studied in the electrical properties. Energy band diagrams of the perovskites materials are studied in electronic properties. 2.2 Theory of perovskite materials : The mineral perovskite (CaTiO3) is named after a Russian mineralogist, Count Lev Aleksevich von Perovski, and was discovered and named by Gustav Rose in 1839 from samples found in the Ural Mountains .The perovskite structure have the Generic formula of Perovskite materials
stoichiometry ABX3, where “A” and “B” are
cations and “X” is an anion. The “A” and “B” cations can have a variety of
charges in the original Perovskite mineral. The “A”
cation is
divalent and the “B” cation is tetravalent. In the cubic unit cell, the Acation resides at the eight corners of the cube, while the B-cation is located at the body center that is surrounded by 6X-anions (located at the face centers) in an octahedral [BX6]-4cluster[57]. In the present work ,“A” can have Methyl ammonium in Organic materials and Cs in Inorganic materials.“B” can have Lead (Pb) or Tin (Sn). “X” can have any halide atom (I ,Br , Cl ) .In the literature review, the Perovskite
material employed absorption layer or harvester light in the Perovskite Solar Cells (PSCs) as shown in figure (2.1a) .
Fig.(2.1) a:illustrate layers and structure of the PSCs . b:Schematic band energy diagram of the PSCs[5]. Generally, PSCs are formed from the following fundamentals layers : Photo-Anode as Electron Transport Layers (ETL) ; which formed of composite of
n-type
Fluorine-Tin Oxide materials
as
transparent conductive layer and TiO2 as compact layer on FTO of PSCs. Absorption layer ; composites of TiO2 or Al2O3 or both of them are carrying
perovskite crystalline materials, scaffold of
perovskite materials , and doing as harvester light in OPCs. Hale Transport Layers (HTL) ; It is well known that composites are highly conductivities, on the order of 10−3 Scm−1. The widely used HTMs, for example, spiro-OMeTAD, CuI, C or polyaniline
are less conductivity (10−5 Scm−1). Its thicker capping layer results in high series resistance [1]. It is indisputable that the HTM is an important role in perovskite solar cells which typically employ a wide varieties of organic polymer hole conductors. Top contact electrode as Al , Ag or Au thin film electrode which deposited on HTM layer . Abridged detail of doing PSCs, when a photon is absorbed by the peroveskite materials(Pm), an exciton is generated and it propagates just until the interface Pm /ETL. At this point the exciton is separated into an electron and a hole, which are collected respectively forward ETL and generic (HTM). In this way the transport of charge is immediately entrusted to ETL and HTM, giving to the Pm only the task of photogeneration. Since the harvest of the light take place only in a monolayer of the sensitizer material , nanoporous structured is used in order to increase active area Pm/ETL. In order to incentives the dissociation of the exciton in free charges, necessary required that the system is composed as ETL/Pm/HTM and has a profile of energy levels such as shown in figure (2.1b). 2.2.1 Photo anodes : Figure 1.3 displays the architecture schematics of three types of photoanodes in perovskite solar cells. Like the architecture of DSSCs, mesoporous metal oxide films in figure 1.3(a), are usually adopted as the working electrodes in the novel construction of perovskite-based solar cells [1,8,33-35]. It was observed that the charge extraction rates were significantly faster for the perovskite-sensitized cells in comparison to the conventional DSSCs during the investigation of the charge-transport properties of perovskite-sensitized solar cells [36]. Solar cells with new architectures of photo electrode for the mesoporous
oxide that
the mesoporous TiO2 was replaced by the insulating
mesoporous Al2O3 or ZrO with a similar meso-morphology were developed. An addition ,
the mesoporous photoanode needs to be
relatively thick, which leads to charge transport and recombination related losses[37]. When considering electron
injection from the
photoactive layer to mesoporous Titania ,as shown in figure 3.4 [38], Voc is determined by difference in the Fermi level of TiO 2 and the HOMO level of the HTM [39] . For mesoporous TiO2 , Schematics of device architecture are sketched in figure 1.3a , a device architecture of TiO2/MAPbI3/Au [33] experimentally confirmed the hole transport properties of MAPbI3. It achieved a PCE of 5.5% with FTO/100nm . For Nano-Rod TiO2 , Schematics of device architecture are sketched in Figure 1.3b, Perovskite light harvesters have also been reported with one-dimensional nanostructures. Rutile TiO2 (∼0.6 𝜇m long) with photoactive MAPbI3 achieved PCE of 9.4% [34]. Increasing the length from 0.6 to 1.6 𝜇m decreased the photovoltaic performance. With an increase in the length of nanorods, the tilted nanorods resulted in problems in pore filling with spiro-MeOTAD. Nano-Rod NRs of ZnO arrays have been employed as photoanodes in perovskite solar cells [8]. It was demonstrated that ZnO NRs offer a fast electron
transport
pathway and the electron transportation time in the ZnO nanorods was slightly shorter than in mesoporous TiO2 films with a similar thickness . The optimized solar cell exhibited an efficiency of 5.0%. When replaced TiO2 with insulator mesoporous oxide as alumina mixed with MAPbI2Cl perovskite coated layer in a photovoltaic cell results in improvement a PCE of 10.9% [40]. This device structure was called “meso-super-structured solar cell” (MSSC) as the photo-generated electrons are not transferred to alumina ,as shown in figure 2.2, because
of the difference in band edges of alumina and perovskite active layer, which acts only as a scaffold for carrying the photoactive layer[39]. Meso-super-structure
concept was also evaluated with ZrO2
mesoporous scaffold with MAPbI3 light harvester exhibiting significant photovoltaic activity Voc of ∼900mV though lower than Titania [41]. Impedance
spectroscopic
study
employing
three
electrodes
electrochemical cell verified that zirconia scaffold was not charged up to a bias of 0.9V in contrast to Titania meso-porous layer indicating that the photo-generated electrons are not injected into zirconia scaffold [41]. A higher efficiency of 10.8% was reported for MAPbI3 sensitizing ZrO2 scaffold with a Voc of 1.07V [6] .
Fig. 2.2 A diagram illustrating the charge transfer and transport in a perovskite-sensitized TiO2 solar cell (left) and a non-injecting Al2O3based perovskite solar cell (right)[38] For planar hetero-junction structured cell as shown in the sketched device in figure 1.3c, thermally co-evaporated CH3NH3I and PbCl2 deposited as perovskite of MAPbI3−xCl3 onto FTO with a thin TiO2 layer resulted in a PCE of 15.4% [42]. Vapor deposited perovskite layer showed an enhanced PCE over solution processed active layer due to increased morphology control and formation of homogeneous flat,
pinhole-free active layer. While the vapor deposited process is easier to obtain a flat active layer of perovskite MAPbI3−xCl3 without mesoporous oxides [39]. 2.2.2 Hole Transport Material (HTM) : At first , the perovskite-sensitized solar cell used redox couple iodide/tri-iodide (I–/I3–) in an organic liquid electrolyte, however, it is highly corrosive, volatile and photo-reactive, interacting with common metallic components and sealing materials. Consequently, it adversely affects long-term performance and durability [13,14,16] . Efforts have focused on using solid-state organic or p-type conducting polymer holetransport materials (HTMs) as Alternative to improve their conversion efficiency. Solar cells using spiro-OMeTAD [9,19,20,26,27,31,32] and PCBM/PFN [25] exhibit the PCE among of 2% to 17.1%. However, the widely used organic hole conductors including spiro-OMeTAD may represent a potential hurdle to the future industrialization of this type of solar cell because of their relatively high cost. To this end, a perovskitesensitized solar cell utilizing an inexpensive, stable, solution-processable inorganic composites of CuI [23] or C [24] as the hole conductor has been demonstrated . It was also demonstrated that the solutionprocessable p-type direct bandgap semiconductor CsSnI3 with perovskite structure can also be used for hole conduction replacing a liquid electrolyte [17]. Perovskite-sensitized solar cells without HTM have low performance exhibit the PCE of 5.5% and 5.3% of ref [15,30], respectively. The trade-off between the series and shunt resistance in perovskite solar cells was controlled somehow by the performance of perovskite and/or HTM. It is well known that perovskite is highly conductive, on the order of 10−3 Scm−3, which requires a thick layer of HTM to avoid pinholes[1]. Low conductivity of HTM is the major reason for low Full Factor (FF) of perovskite solar cells which can be
remedied by doping the HTM with p-type codopant. Lithium salt LiTFSI added to spiro-MeOTAD increases the hole conductivity in spiroMeOTAD and improves of the PCE of perovskite solar cells [9,19,27,32,39] ,as shown as in the table 1.1. Photoelectron spectroscopy combined with absorbance measurements revealed that the Fermi level in spiro-MeOTAD is shifted toward HOMO due to the oxidation of 24% spiro-MeOTAD molecules by the addition of Li-TFSI [43]. Protic ionic liquid has also
been used recently as p-dopant to HTMs [44]. In
addition to use of doping technique to improve the FF, improving the morphology (defect- and pinhole-free) of the active layer enhances the FF and the performance of perovskite solar cells by enhancing the conductivity of HTM and reducing the series resistance. Establishing perfect p–n contact between active layer and HTM also improves the fill factor caused to improve the performance PSCs. Chemical modification can be used to fine-tune this contact between organic and inorganic layers from HTM and perovskite, respectively [39]. 2.2.3 Manufacturing and possesses : The preparation of MAPbI3-xClx film from different deposition methods such as, dual source co-evaporation using PbCl2 and MAI source, sequential deposition by dipping the PbI2 film into MAI solution , one-step solution process based on the mixture of PbI2 and MAI, and two-step sequential coating of PbI2 and MAI, vapor-assisted solution process using the MAI organic vapor to react with the PbI 2 film, as shown in figure 2.3 [10, 45-48]. The typical two methods are available that one-step and two-step coating methods. Perovskite forms either by spin-coating a mixed CH3NH3I and PbI2 solution (one-step coating) or by spin coating CH3NH3I after coating with PbI2 (two-step coating) [48].
For the one-step coating method, CH3NH3I and PbI2 are dissolved in an appropriate solvent such as a polar aprotic solvent like N,N dimethylformamide (DMF), gamma-butyrolactone (GBL), or dimethyl sulfoxide (DMSO), and this is used as a coating solution. Drying and annealing processes are followed by spin coating. For the two-step coating method, PbI2 solution is first coated on the substrate to form a PbI2 film and then a 2-propanol solution of CH3NH3I is spun on the PbI2 film. Figure 2.3c shows schematically the procedure for both the onestep and two-step spin-coating methods. In order to prepare high-quality perovskite films, it is important to adjust coating parameters such as spinning rate and time, temperature, solution wettability and viscosity, etc.
Fig.2.3 depicted the different deposition methods ,(a) co-evaporation coating (b) Dipping coating (c) One-step and two-step coating (d) Vapor-assisted solution process coating [10, 45-48]. Compared to one-step spin-coating, two-step spin-coating found to exhibit better photovoltaic performance due
was
to better
morphology and interfaces, [48-51] which reports showed that full
coverage of the perovskite film on the substrate surface is necessary to ensure sufficient shunt resistance and indicates that morphology control of perovskite film is crucial in achieving high-efficiency perovskite solar cells. Perovskite prepared by the two-step coating method shows cuboid-like crystals, whereas the one-step method from the dimethyl acetamide (DMA) solution of CH3NH3I and PbI2 produced a shapeless morphology [52]. 2.2.4 Charge transfer mechanisms : Light absorption, charge separation, charge transport, and charge collection are general solar cell working processes. In order to construct them, light harvesters should be selected and their opto-electronic properties investigated. For instance, a p-i-n junction is required in case the light harvester is an intrinsic revealed that charge diffusion lengths were about 1 μm for both samples, but the diffusion length for holes was longer than that for electron in the MAPbI3 perovskite [53,54] . Concrete evidence of balanced long-range electron-hole diffusion lengths of at least 100 nm in solution-processed MAPbI3 was obtained by applying femtosecond transient optical spectroscopy to bi-layers that interface this perovskite with either selective-electron or selective-hole extraction materials [1,55]. It is found that both electron and hole diffusion lengths are >1 μm for the mixed-halide (I and Cl) perovskite a factor of ∼5 to 10 greater than the absorption depth. To compensate the shorter electron diffusion length, an electron transport layer with a long diffusion length may be required for MAPbI3 . Electron
diffusion
lengths of MAPbI3 solar cells employing mesoporous TiO2 layers are estimated to exceed 1 μm [56]. Electron
and hole moblities
were
found to be as high as 25 cm2 /Vs, and the mobilities of both were almost balanced and remained high, on a microsecond time scale, along with a slow microsecond time scale for recombination. [57] However,
the performance may degrade if the mobility of the injected electron in the TiO2 layer is slower than that of perovskite. Therefore, careful design of oxide layers, taking into account this diffusion length and the mobility of the injected electrons,
is important to achieve high
efficiency. Based upon the unique property of the perovskite, two typical structures can be constructed: a mesoscopic nanostructure and a planar structure, mesoscopic nanostructures with perovskite pore fillings figure 2.4a and planar structures without a mesoporous TiO2 layer figure 2.4b, because of charge transport and charge accumulation properties in the perovskite. In the mesoscopic structure, electrons can be collected directly and/or via TiO2 layer. Carrier transport and recombination were compared for the mesoscpoic structure and the planar structure; in figure 2.4, the former was lower in efficiency than the latter, and found to be the main factor affecting photovoltaic performance. figure 2.4 shows schematic device structures and energetic of transport electronhole.
Fig. 2.4 (a) Mesoscopic perovskite solar cell with mesoporous TiO2 layer and (b) planar structure without a mesoporous TiO2 layer. (c) Schematic diagram of energy levels and electron transfer processes in an HTM/perovskite/TiO2 cell [54,57] .
Charge separation by electron injection from perovskite to TiO2 is obvious in cases where perovskite dots are adsorbed onto the TiO2 surface[54] . The electron transfer processes according to life time of recombination
electron-hole in an HTM/perovskite/TiO2 cell
as
successive processes are (1) Electron injection; (2) hole injection; (3) radiative
exciton
recombination;
(4)
non-radiative
exciton
recombination; (5) back electron transfer at the TiO2 surface; (6) back charge transfer at the HTM surface; (7) charge recombination at the TiO2/HTM interface, as shown in figure 2-4c[57]. 2.3 Challenges : The several problems related to OPSC from where manufacturing and performance such as stability ,Toxicity and hysteresis effect . 2.3.1 Stability : Two parameters important for commercial application of perovskite solar cells are stability and efficiency. Lots of research effort has been directed at enhancing the efficiency of these devices by adoption of various
device
architectures,
compositions,
and
manufacturing
techniques. This has resulted in substantial increase in efficiencies to be proven efficiency of 20%[58]. The limiting factor to this success story is the efficiency. High efficiency devices reported are synthesized under controlled environments and lose their efficiencies rapidly. For their commercial viability it is imperative
that studies be undertaken on
issues of stability and reproducibility to enhance the lifetime of these devices. Degradation in perovskite solar cells is a synergetic effect of exposure to humidity, oxygen, ultraviolet radiations, and temperatures. Niu et al. have proposed a sequence of chemical reactions considered responsible for the degradation of CH3NH3PbI3 moisture [59]:
in the presence of
𝐻2 𝑂
𝐶𝐻3 𝑁𝐻3 𝑃𝑏𝐼3 (𝑠) ↔ 𝑃𝑏𝐼2 (𝑠) + 𝐶𝐻3 𝑁𝐻3 𝐼(𝑎𝑞) … . . (2 − 1) 𝐻2 𝑂
𝐶𝐻3 𝑁𝐻3 𝐼(𝑎𝑞) ↔ 𝐶𝐻3 𝑁𝐻2 (𝑎𝑞) + 𝐻𝐼(𝑎𝑞) … . . (2 − 2) 𝐻2 𝑂
4𝐻𝐼(𝑎𝑞) + 𝑂2 (𝑔) ↔ 2𝐼2 (𝑠) + 2𝐻2 𝑂(𝑙) … . . (2 − 3) 𝑈𝑉
2𝐻𝐼(𝑎𝑞) ↔ 𝐼2 (𝑠) + 𝐻2 (𝑔) … . . (2 − 4) The equilibrium species, in the presence of water, oxygen, and UV radiation, are thus CH3NH3I, CH3NH2, and HI. HI can either decompose by a one-step redox reaction, equation (2-4), or by photochemical reaction under UV radiation to H2 and I2. This sensitivity requires synthesis in a controlled environment like a glove box [10, 35]. A humidity of 55% is reported to deteriorate performance and is evident by a color change from dark brown to yellow [34]. To prevent this effect , alumino silicate used as shell on titania nanoparticles can increase stability [60]. Al2O3 scaffold is a more stable alternate to TiO2 in MSSC [61, 62]. CH3NH3PbBr3 is reported to be more stable to moisture exposure and CH3NH3Pb(I1−xBrx)3 based absorbers retained good PCE on exposure to humidity of 55% for 20 days [49]. Inclusion of Sb2S3 layer at the interface between mesoporous TiO2 and perovskite layer was observed to increase the
stability,
attributed to the interruption of iodide couple at the interface[61]. Thermal stability studies are important as under solar illumination the temperatures are expected to be over the phase transition temperature of CH3NH3PbI3. It changes from tetragonal to cubic structure at 56 0C [63]. Use of polymers with single-walled CNTs as aHTL has been reported to increase the thermal stability and
retard moisture sensitivity of the
perovskite solar cells [64]. 2.3.2 Toxicity : Lead compounds are very toxic and harmful to the environment . Lead compounds are toxic if ingested, if its dust is inhaled, or if it is handled
improperly
(i.e.
without
appropriate
gloves
and
other
safety
precautions). The health risks and dangers of CH3NH3PbI3 are concentrated in contact CH3NH3PbI3 with polar solvents such as water can convert to PbI2, a carcinogen, that is moderately water-soluble and whose use is banned in many countries [65]. Therefore it seems that identifying lead-free perovskites or other pigments that can replace CH3NH3PbI3 is necessary for the widespread deployment of PSCs. The tin analogues CH3NH3SnI3 [27] and CsSnI3 [17] show promising future to development of perovskite solar cells. 2.3.3 Hysteresis effect : The appearance in the (I-V) curves of strong hysteresis which consists of the anomalous dependence of the PCE on the voltage scan direction and speed, published PCE values as shown in figure 2-5, that reported in ref [65,66].
Fig. 2.5 Stabilized power output from an MSSC. Forward bias to short circuit (FB-SC) and short circuit to forward bias (SC-FB)[66]. The results by Seok et al show that the appearance of hysteresis for thicker mesoporous TiO2 voltage
layers and reported that by reducing the
scan speed it is possible to fully suppress this anomalous
behavior in solar
cells , also
exhibit
the
hysteresis
effect is
particularly severe for planar device configurations [67]. High hysteresis effect were measured for planar perovskite and Al2O3 based cells (up to 50%), whereas TiO2 based cells showed a much more limited effect (up to 15%)
as reported in ref [66].
The polarization phenomenon in
perovskite materials probably causes current–voltage hysteresis. Anomalous I–V hysteresis, differences in I–V curves depending on scan direction, was observed from CH3NH3PbI3-xClx [66] and CH3NH3PbI3 . [68] Such I–V hysteresis was found to be strongly dependent on perovskite crystal size and the presence of a mp-TiO2 film, where largesized perovskite and the presence of mp-TiO2 would suppress I–V hysteresis. [68]. Understanding the ferroelectric behavior of this class of materials may be critical in increasing efficiency and stability of PSCs as ferroelectricity may affect the photoexcited electron hole pairing and separation [69,70]. The origins of this effect are still postulated . 2.4 Basic Terms for Photovoltaic Performance : In general photovoltaic (PV) cells, can be modeled as a current source in parallel with a diode. As the intensity of light increases, current is generated by the PV cell. Where there is no light, the PV cell behaves like a diode, (I-V) curve passed of original point (I = 0A, V = 0V) as shown in figure 2.6 [71].
Fig. 2.6 (a) I-V Curve of photovoltaic (PV) cell in darkness and under illumination; (b) Electrical diagram of a PV cell [71].
The total current I in an ideal cell is equal to the current Il generated by the photoelectric effect minus the diode current ID, according to the equation below[71]: 𝑞𝑉
𝐼 = 𝐼𝑙 − 𝐼𝐷 = 𝐼𝑙 − 𝐼0 (𝑒 𝑘𝑇 − 1) … . (2 − 5) where I0 is the saturation current of the diode, q is the elementary charge 1.6 × 10−19 Coulombs, k is a Boltzmann's constant of value 1.38 × 10−23 J/K, T is the cell temperature in Kelvin and V is the measured cell voltage. When taking into account the series and shunt resistances, equation 2-5 can be expanded to Equation (2-6): 𝐼 = 𝐼𝑙 − 𝐼0 (𝑒
𝑞(𝑉+𝐼𝑅𝑠 ) 𝑛𝑘𝑇
− 1) −
𝑉 + 𝐼𝑅𝑠 … . (2 − 6) 𝑅𝑆𝐻
Rs and Rsh are series and shunt resistances which obtained from Light IV Measurement Test Reports of solar cells system or calculated from reverse of slope of light I-V curve at I= 0 and V= 0, respectively[72]. When the voltage is equal to zero, the short circuit can be calculated (Jsc); The Jsc occurs at the beginning of the forward bias sweep. On the other hand, the open circuit voltage occurs when no current passes through the cell. The solar cell is operated over a wide range of voltages (V) and currents (I). By continuously increasing the applied voltage on an illuminated cell, from V = 0 (with a short circuit current, Jsc), through the point of I = 0 (with an open circuit voltage, Voc), to a very high value of V, it is possible to determine the maximum-power point at which the cell delivers maximum electrical power; thus, Vm × Im = Pmax in Watts. From that point on, the fill factor, defined as FF = Pmax/(IscVoc), is determined. A larger fill factor is desirable and corresponds to an I-V sweep that is more square-like. Fill factor is also often represented as a percentage. The power conversion efficiency (η), defined as the
percentage of the solar power that is converted from absorbed light to electrical energy, is estimated as the equation 2-7: 𝜂=
𝐹𝐹 ∗ 𝑉𝑜𝑐 ∗ 𝐽𝑠𝑐 𝑃𝑖𝑛 ∗ 𝐴𝑎𝑐
… (2 − 7)
Where Aac is active area of solar cell and Pin is the input light irradiance which illuminates the cell [71]. The optical band gap of the thin film have been investigated for the allowed direct transition in accordance with the theory of Bardeen et al from the equation (2-8) [73]. αℎ𝑣 = 𝐵 ∗ [ℎ𝑣 − 𝐸𝑔 ]
1⁄2
… (2 − 8)
Where, h is the Planck constant, (α) is the absorption coefficient ,ν is the light frequency , Eg is the optical energy gap and B is empirical constant. (α) is given by the equation (2-9) . 𝐴 α = 2.303 ∗ ( ) … (2 − 9) 𝑡 Where, A is the absorbance and (t) is the thickness of the film . 2.5 Structures of perovskite materials : perovskite materials as oxides and halides are typical representatives of perovskite compounds, although the perovskite-type structure can also be formed by various classes of inorganic compounds, as sulphides, halides,
cyanides,
oxyfluorides,
oxynitrides,
intermetalic,
and
metalorganic compounds. The diversity of chemical elements, which form perovskite structures , their ability to create cation- or aniondeficient structures, and a rich variety of distorted perovskite structures lead to an extremely broad range of physical properties. This family of materials is known to exhibit the extraordinary properties and exciting phenomena ferroelectricity,
such
as
superconductivity,
magnetoelectricity
magnetoresistance,
,anti-ferromagnetism,
anti-
ferroelectricity, etc . The types of perovskite structures in the Space
Groups (SG) of materials are categorized in the table (2.1) and shown in the figure 2.7 [74]:
Fig. (2.7) depicted the SG of perovskite materials structures [74]. Table (2.1) indicated to the SG and perovskite materials structures[74]. SG of structures Cubic Pm3m structure Rhombohedral R3c structure Orthorhombic Pbnm structure Orthorhombic Imma structure Tetragonal I4/mcm structure Monoclinic I2/m structure Triclinic I-1 structure Hexagonal P63cm structure
lattice parametersap ,bp, cp
2.5.1
Tolerance factor and transformation phase of perovskite
materials: The degree of distortion of a perovskite from ideal cubic structure was measured by the constant which is known as the tolerance factor (t). Therefore , the closer the value of the tolerance factor
to
cubic
structure is to unity and given with eq (2-10) [74]. RA + RX = t √2*(RB + RX)…..( 2-10 ) Where RA, RB and RX are radiuses of A,B and X atoms , respectively. On the basis of tolerance factor values, it has been proposed [74] that compositions
with 1.00 < t < 1.13 will exhibit hexagonal symmetry.
Limiting values for the tolerance factor have been determined through experiment. Martin A. et al. suggested that the perovskite will be cubic if 0.9 < t < 1.0, and orthorhombic if 0.75 < t 26 mm-1) and conductivity, in contrast to the α- phase. However, a possible phase transition from β-phase to α-phase may occur under continuous 1 sun illumination .
As the temperature decreases, the cubic phase is
transformed to the tetragonal phase, as shown in figure 2.10 and Table (2.2) [78].
Fig. 2.10(a) Graphical scheme of observed phase transitions of MA(Pb,Sn)X3 [77]. (b) The structure transformation from cubic to orthorhombic in MAPbI3[78] and (c) the lattice contact change with different amounts of Br incorporation [77].
Table 2-2 Crystal systems and transition temperatures of CH3NH3PbX3 (X=Cl, Br or I)[78]. Material
CH3NH3PbCl3
CH3NH3PbBr3
CH3NH3PbI3
Crystal system
Cubic
Cubic
Cubic
Transition temperature (K)
177
236
330
Crystal system
Tetragonal
Tetragonal
Tetragonal
Transition temperature (K)
172
149-154
161
Crystal system
Orthorhombic
Orthorhombic
Orthorhombic
Phase transformation can occur in mixed halide systems . As well as to use a mixed halide MAPbI3-xBrx (0 ≤ x ≤ 3) for band-gap tuning and observed that the crystal structure transformed
from the tetragonal
phase to a cubic phase when the percentage of Br present passed a threshold of approximately x ≈ 0.5, as shown in figure 2.10c[77]. This phase transition has been presumed to explain the improved stability of MAPbI3-xBrx materials in the air and humidity test, making it an interesting
addition to our
understanding of the specifics of the
perovskite lattice. Structural parameters of cubic CH3NH3PbCl3 and CH3NH3PbBr3 at RT have similar structure parameters compared with the cubic CH3NH3PbI3, except for the lattice constants. Lattice parameters of these compounds are strongly dependent on the size of halogen ions, as shown in figure 2.11.
Fig. 2-11 Lattice constants of CH3NH3PbX3 (X=Cl, Br, or I) [78]. Ion radii of halogen elements increase with increasing atomic numbers, which affect the
lattice constants of CH3NH3PbX3, as
observed in figure 2-11 [78]. 2.5.2 X-Ray Diffraction of perovskite materials : The X-ray diffraction will indicate that the sample is a single phase or mixed phases. Takeo Oku was investigated
Microstructure of the
perovskite phases by (XRD). The diffraction patterns of the CH3NH3PbI3 with cubic, tetragonal and orthorhombic structures was explained in figure 2.12 , Reflection positions of 211 and 213 inconsistent with cubic symmetry for tetragonal structureare indicated by asterisks, which would be helpful for the distinction between the cubic and tetragonal phase [78,79].
Fig. 2.12. XRD patterns of CH3NH3PbI3 with cubic, tetragonal and orthorhombic structures[78]. Figure 2.13 depicted plot of (XRD) demonstrated the cubic perovskite structure of CH3NH3PbBr3 powder sample at the room-temperature was investigated by D. Priante, et al [80].
Fig. 2.13. XRD profile of CH3NH3PbBr3 powders[80]. Figure 2.14 displayed
the XRD patterns of
the mixed halide
perovskite structure of CH3NH3PbI3-xClx samples annealed at different temperatures was exhibited the tetragonal CH3NH3PbI3 phase and can be confirmed by reflections positions of (110) and (220) [29,81].
Fig. 2.14 XRD pattern of glass /CH3NH3PbI3-xClx samples annealed at different temperatures for 3 hours in an argon-filled glove box[81].
The XRD spectra illustrated in figure 2.15a was shown the crystallographic structure of the mixed halide
perovskite structure
ofCH3NH3PbI3-x Brx samples. In all cells where Br− ions are involved, the diffraction peaks correspond to the cubic structure, although in the case of CH3NH3PbI3 (where there are no Br− ions), the peaks are related to the tetragonal structure. Figure 2.15b shows a magnification of the XRD spectra in the range of 27° ≤ 2θ ≤ 31°.The position of the (002) diffraction peak for the samples is concentrations. In the case of the
changed according to the Br− CH3NH3PbI3, two peaks can be
observed, indexed as (220) and (004) related to the tetragonal structure. These two diffraction peaks are merged into one when introducing the Br into the perovskite structure [29].
Fig. 2.15 (A) XRD of CH3NH3PbI3-xBrxof the mixed halide perovskite structure. (B) XRD spectra in the range of 27° ≤ 2θ ≤ 31°. “c” corresponds to cubic and “t” corresponds to tetragonal [29].
When (B = Sn ) for (ABX3) perovskite compounds ,Feng Hao et al[27] were reported that crystallizing of CH3NH3SnI3-xBrx (x = 0,1,2 and 3) compounds at the P4mm space group and The properties of the solid solutions are clearly displayed a continuous contraction of the lattice parameters from the CH3NH3SnI3 to CH3NH3SnBr3 end members,
which results in a widening of the bandgap . Figure 2.16 depicted XRD of CH3NH3SnI3-xBrx compounds (x = 0,1,2 and 3) were prepared by mixing stoichiometric amounts of CH3NH3X and SnX2 (X = Br, I), finely homogenized in a mortar in the nitrogen glove box. The resulting solids were sealed in silica ampules under 1 × 10 -4 mbar vacuum
and
heated to 200 oC to complete the reaction[27].
Fig. 2.16 illustrated XRD of CH3NH3SnI3-xBrx compounds[27] For (A=CH3CH2NH3+) of perovskite Hyeok Im et al [16] were
structure (ABX3) ,Jeong-
reported that (CH3CH2NH3)PbI3
have
orthorhombic unit cell with a = 8.741 Å, b = 8.147 Å , c = 30.309Å and possible space groups are P21mn and Pmmn . Figure
2.17
shows
the
XRD
pattern
of
the
synthesized
(CH3CH2NH3)PbI3 . Reflection conditions (h + k=2n for hk0, h=2n for h00, and k=2n for 0k0) [16].
Fig. 2.17 illustrated XRD of (CH3CH2NH3)PbI3 compounds[16] For (A = HC(NH2)2+ ) of
perovskite
structure (ABX3), figure
2.18 was depicted X-ray diffraction spectrum for a smooth and continuous HC(NH2)2PbI3 film such as those used in the high-efficiency devices and quenching films[ 82].
Fig. 2.18 illustrated XRD of HC(NH2)2PbI3compounds[82] Peaks labelled with a * are assigned to the fluorine doped tin oxide substrate, those with a # to PbI2 impurities , and other peaks are assigned to the labeled reflections from a tetragonal perovskite lattice with unit
cell parameters a=b=8.99Å,c=11.0Å, in good agreement with the previous report on HC(NH2)2PbI3 [20,82] 2.6 Optical properties of perovskite materials MAPbX3-based materials exhibit attractive optical properties as the p– p transition and direct bandgap result in a higher absorption coefficient (α). The high α value (>105 cm-1) provides a great potential to fully utilize the photon energy larger than the bandgap and delivers high J sc from thin film (≈ 300 nm) devices. MAPbX3based materials could achieve highest PCE for a given thickness . Moreover, the high Voc value (≈1.15 V) was achieved on MAPbI3 devices relative to its optical bandgap (≈1.5 eV). The small Voc deficit of the MAPbI3 device can be attributed to the less deep defect states and efficient interface contacts. The Urbach energy of 15 meV in MAPbI3 which is closer to high quality GaAs materials. The results indicated the lower possibility of non-radiative recombination that can occur
in the MAPbI3
materials[58]. Belen Suarez et al[28] reported that Perovskite Samples (PS) are denoted as MAPb(BrxI1−x)3−yCly, where x is determined by the ratio between
Br and I precursors but y is not determined due to
researchers are thought that the effect of Cl synthesis is still controversial; just
the
precursor in the PS
extremely reduced amounts of Cl
have been detected in MAPbI3−yCly or even have not been detected. The exact effect of Cl in terms of changing the electrical properties or modifying the crystallinity of the PS is not known[28]. A picture of complete PS photovoltaic devices prepared with a combination of the three halides in a different ratio, MAPb(BrxI1−x)3−yCly, where 0 ≤ x ≤ 1, is shown in figure 2.19a. It can be appreciated at first sight how the color of the absorber films is tuned from dark brown to yellow by controlling the amount of Br[28]. Figure 2.19b was depicted absorption spectra of
the samples (absorption tail observed at long wavelengths is due to the mesoporous layer light scattering). Figure 2.19c was depicted the energy band gap extracted from the absorption measurements depending on the percentage of the Br. Then MAPbBr3 devices are corresponding to the optical band-gap value of (2.3eV)[ 28].
Fig. 2.19(a) Picture of MAPb(BrxI1−x)3−yCly , (0 ≤ x ≤ 1) devices with different Br/I molar ratios grown on mesoporous TiO2 substrates. (b) Absorption spectra of the of MAPb(BrxI1−x)3−yCly, (0 ≤ x ≤ 1) samples. (c) The energy band gap as function of the percentage of the Br(x)[28]. When using the lead-free perovskite of methylammonium tin iodide (CH3NH3SnI3) as the light-absorbing processed solid-state photovoltaic
material to fabricate solution-
devices. Featuring an even lower
optical bandgap of 1.3 eV than the 1.55 eV achieved with CH3NH3PbI3 [48,38] , devices with CH3NH3SnI3 in conjunction with an organic spiroOMeTAD hole-transport layer showed an absorption onset of 950 nm as shown in figure 2.20a. Further chemical alloying of iodide with bromide provides efficient energetic tuning of the band energy structure
of the CH3NH3SnI3-xBrx (x = 0, 1, 2, 3) perovskites comparative with HTM , spiro-OMeTAD , as shown in figure 2-20b [15] . The experimentally observed bandgaps for CH3NH3PbX3 with tetragonal 1.55, 1.78, and 1.55eV for X = I, Br, and Cl, respectively, and cubic 1.55 , 2.00 and 3.11 eV for X = I , Br , and Cl, respectively, structures. Figure 2.20c shows the optical band-gap, valence band maximum VBM , and conduction band maximum CBM for ABX3 (A = MA and FA,B = Pb, Sn or Sn1-xPbx , X = Cl, Br, I or I1-xBrx) [84,38].
Fig. 2.20 (a) absorption spectra of the CH3NH3SnI3-xBrx when (X= 0, 1, 2, 3) perovskites . (b) Schematic energy-level diagram of CH3NH3SnI3-xBrx with TiO2 and spiro-OMeTAD HTM [27] , (c) Schematic energy level diagram of MAPbBr3, MAPbI3, FAPbI3, MAPb1-xSnxI3 , and MASnI3 along with MASnI3 .
2.7 Electric properties of perovskite materials: The real part of the dielectric permittivity (dielectric constant) ε′ was investigated with temperature (phase) for MAPbX3 in Ref [48] . ε′ was higher for the tetragonal phase in temperatures ranging from180 to 300 K, compared to the orthorhombic phase at lower temperature, in which ε′ increased as the halide anion in MAPbX3 changed from Cl (ε′ ≈ 40 at 300 K and ≈ 60 at 200 K), to Br (ε′ ≈ 50 at 300 K and ≈ 70 at 200 K) and I (ε′ ≈ 60 at 300 K and ≈ 100 at 200 K) at 100 kHz. In the lowtemperature orthorhombic phase, ε’ was as low as 17, 26, and 36 for Cl, Br and I, respectively, and temperature independent, which indicates that electronic or ionic polarization is expected from the orthorhombic phase. Figure 2.21 shows the dielectric constants frequency [48], where electronic polarization
as a function of
arises when the local
electronic charges around the nucleus are displaced under the electric field, and ionic polarization results from the displacement of cations and anions in opposite directions under an electric field in ionic materials , whereas
orientational polarization can occur in substances
with
molecules that have permanent electric dipoles. Figure 2-21(a) explains Schematic of different contributions to polarizability as a function of frequency and (b) the real permittivity as a function of frequency for different incident light intensities from dark to 1 sun (100 mW/cm2) for MAPbI3-xClx perovskite device with configuration of architecture (compact TiO2 / MAPbI3-xClx in Al2O3 scaffold / spiro-OMeTAD ), measured at room temperature and 0 V applied bias. linear regression of dielectric constant vs. illumination intensity at frequency f = 50 mHz was observed a close-to-linear dependence between ε0 and illumination intensity [48].
Fig. 2.21 . (a) Schematic of different contributions to polarizability as a function of frequency (b) the real permittivity as a function of frequency for different incident light intensities [48]. The orientational polarizability (αor) depends on temperature : αor=P2/3kT where k is the Boltzmann constant and T temperature . Giant dielectric
constants, approaching 107, are observed
perovskites upon illumination especially at shown
in
from
low frequencies, as
figure 2.21b [48] which is related
to
the molecular
orientation of A-site CH3NH3+ions . Sn-based perovskites such as CsSnBr3 and CH3NH3SnI3
were found to exhibit high electrical
conductivity , which might be closely related to the infinite linear –I– Sn–I–Sn– chains formed three-dimensionally in the perovskite lattice.
For the case of Sn-based bromide perovskite environment coordinated with bromide
materials, the Sn
was found to be critical to
determine the electrical properties. According to reviews studies on a perovskite solar cells
of
CH3NH3Sn1-xPbxBr3 and CsSnBr3 by Hyun Suk Jung and Nam-G Park [48] , the high electrical conductivity of the CsSnBr3 decreased drastically upon replacement of Cs and
Sn by CH3NH3 and Pb ,
respectively, due to change in the local octahedral environment
of
SnBr6 and the Sn–Br–Sn bond length [48].
2.8 Electronic properties of perovskite materials : Early studies on the electronic band structures of organic– inorganic (3-D and low-dimensional) perovskites was traced to the studies of Tze
Chien Sum and Nripan Mathews [75]. They reported that
calculations of principles density functional theory DFT at the room temperature cubic phase for the 3-D CH3NH3PbI3 crystal revealed that the valence band maxima comprises the Pb 6p–I 5p s-anti-bonding orbital , while the conduction band minima consists of Pb 6p–I 5s s-antibonding and Pb 6p–I 5p p anti-bonding orbitals (see figure 2.22)) [75]. In the work of Mosconi et al [84], they calculated the band structure for CH3NH3PbX3 (cubic phase) and the mixed halide CH3NH3PbI2X (tetragonal phase) (X =Cl, Br and I) with the surrounding CH3NH3+ counter ions, which were ignored in the earlier studies.
Fig. (2.22) Bonding diagram of (a) [PbI6]4- cluster (0-D), (b) CH3NH3PbI3 (3-D) and (C4H9NH3)2PbI4 (2-D) at the top of the valence band and at the bottom of the conduction band [57]. Nevertheless, the organic component had little influence on the bandgap energy, of which is mainly determined by the [PbI4]6- network. In addition, the authors highlight that the
close matching of their
calculated bandgaps (where spin-orbit-coupling (SOC) effect were not considered) with the experimental data is likely to be fortuitous. These findings are consistent with the studies by Baikie et al.[79] and Y. Wang et al.(low-temperature orthorhombic phase) [85]. Investigation on the SOC effect on the electronic band structure in 3-D perovskites (lowtemperature orthorhombic phase) was reported by Even
et al, [86],
where they found that the SOC dramatically reduces the
energy gap
affecting mainly the conduction band.
Chapter Three
Characterization Techniques
Deposition processes Techniques
Fabrication (OPSCs, OIPSCs and FLPSCs) devices
3.1 Introduction : This chapter presents the description of the procedure implemented in our research for the manufacturing
the Organo-lead halide
Peroveskite Solar Cells (OPSC) of devices and Organic-Inorganic Peroveskite Solar Cells (OIPSC) devices. At first, characterization techniques
for testing the peroveskite
materials
which used
for
preparation OPSCs, OIPSCs and FLPSCs are described. In this chapter, X-ray diffraction, AFM UV/Vis Double
microscope, SEM microscope, SPECTRO
Beam, and Light I-V Measurement System are
explained. In addition, deposition techniques
and synthesis materials
for the manufacturing devices are described in this chapter. 3.2 Characterization Techniques : Composition and crystal structure of the thin films
and powder
preparation samples were studied by X- Ray Diffraction (XRD). The surface morphology of sample was studied by investigation of Atomic Force Microscopy (AFM) .The difference in the shape of the perovskite crystals studied by images of Scanning Electron Microscope (SEM). Light I-V Measurement Test Reports were recorded by Photovoltaic measurements system. Optical properties such as the absorption , the energy gap and transmittance of the film coated are investigated by UV-Vis absorption spectrophotometer . 3.2.1 Structural studies X-Ray Diffraction : The crystal graphic orientations of perovskite materials were analysis by XRD (Shimadzu 6000) using Cu-Kα target and radiation of wave length 1.5406 A. XRD Patterns were recorded at a scanning rate of 5 (deg/min), applied voltage and current of target are 40.0 (kV) and 30.0 (mA), respectively. The structure of perovskite materials was investigated by comparison of the prominent peak positions (2θ -values)
of the XRD spectra with the ASTM data file (American Society for Testing and Materials ) and the references in the literatures survey. 3.2.2 Morphological studies : 3.2.2.1 Atomic Force Microscope : The surface morphology and nanoparticle average dimensions of the samples of thin film of compact layer of TiO2 of OPSCs were studied by investigation of Atomic Force Microscopy (AFM) (AA3000 Scanning probe microscope, Angstron Advanced Inc.).as
shown in
figure (3.1a). AFM is instrument of measuring the topography of a given thin film. A nano-sized tip attached on a cantilever is traded over the surface sample which placed on Piezo-electric moved at ZTapping (PZT) scanner and a 3D image of the topography of the surface sample is generated on a computer , as shown in Fig (3.1b) . The advantage
of the AFM over SEM is the ability to make
topographical measurements for detection and investigation of the particle size and shape of TiO2 compact layer sample in 3-Dimensions . In addition
AFM is
given chart plot of grain size
percentage
distribution in 2D-image of samples .
Fig (3.1) : depicts the scheme of operation principles of AFM for measurement of sample.
3.2.2.2 Scanning Electron Microscope : The difference in the shapes of the perovskite crystals materials is studied by the images of Scanning Electron Microscope (SEM) (TESCAN (Vegaш)), analysis is performed
by using a magnification 100kx and
500kx, high voltage 10kV and SEM in secondary electron mode. The SEM works at the same principle as an optical microscope, but instead of using photons reflections of the surface sample it using the electrons scattered to measure the images. As consequence, the wave length of accelerated electrons can be shorter than the one of photons due to the accelerated electrons are scattered by an electric potential of the nuclears of the atoms in the crystalline
structure. This makes the SEM capable of
magnifying images up to 500.000 times.
An addition, it is possible to
achieve high resolution pictures of the surface, making the device very useful in determining the size distribution of nano-particle. The scheme of operation principles of SEM device is shown in figure (3.2).
Fig(3.2) depicts the scheme of operation principles of SEM .
3.2.3 Optical properties studies : The transmittance and absorption of the film coated is measured in the wavelength range of (400 - 800) nm at room temperature using a ( SPECTRO UV/Vis Double Beam (UV-2601) BIOTECH ENGINEERING
MANACEMENTCO LTD, Inc ),
as
shown in
figure(3.3). A blank sample of substrate is used as a reference in the measurement of optical transmittance. The optical band gap of the thin film have been investigated for the allowed direct transition in accordance with the theory of Bardeen et al from the equation (2-4) and absorption coefficient (α) is given by the equation (2-5) [73].
Fig(3.3) depicts the schematic diagram of UV/Vis spectrophotometer . 3.2.4 I-V and Parameters Characteristics of Solar Cells studies : Light I-V Measurement Test Reports of OPSCs are recorded by Photovoltaic measurements system, Integrated cell tester CT100AAA, Photo Emission Tech Inc. It is composed of Oriel I−V test station CCSERIES using an Oriel Solar simulator SS100, Keithley model 2400 digital source meter to calculate the variable load of OPSCs and a computer for storing of data, as shown in figure 3.4. The solar simulator is class AAA for spectral performance, uniformity of irradiance ,and
temporal stability. The solar simulator is equipped with a450 W xenon lamp. The output power is adjusted to match AM1.5 global sunlight (100mW cm−2) . The solar simulator is useful to supply suitable sunlight and to provide a controllable indoor test facility under laboratory condition . For photovoltaic testing exist three standards that define solar simulator performance: International Electrotechnical Commission (IEC) 60904-9 Edition 2 (2007) (Photovoltaic Devices) ,Japanese Industrial Standard (JIS) C 8912-1998(Solar Simulators for Crystalline Solar Cells and Modules) and American Society for Testing and Materials (ASTM) International E 927-05 (2005) (Specification for Solar Simulation for Terrestrial PV)[ 87]. Spectral match: All standards define the spectral match of a solar simulator as a percentage of integrated intensity in six spectral range for the best typical standard spectrums AM1.5G. Any deviation from the specified percentages must then lie within a range that determines the class of the simulator . Table 3.1 is reported the spectral contents by IEC 60904-9 Edition 2 (2007) (Photovoltaic Devices) for AM 1.5G spectrum . Spatial uniformity of irradiance: In order to avoid significant errors in measured cell efficiency , is needed that the irradiance has sufficient spatial uniformity. For this, every solar simulator has a working distance range in which is ensured the constraint on spatial uniformity . Temporal stability: It requires that the output light be stable over time in order to ensure that the lamp fluctuations do not distort the measurement of solar cell efficiency .
Table 3.1: Ideal spectral match definite by IEC standards for AM 1.5G Spectral Range (nm)
Total Irradiance
Ideal (%)
Range (%) 400 – 500
13.9 - 23.1
18.5
500 – 600
15.1 - 25.1
20.1
600 – 700
13.7 - 22.9
18.3
700 – 800
11.1 - 18.5
14.8
800 – 900
9.2 - 15.3
12.2
900 – 1000
12.1 - 20.1
16.1
Light I−V curve of the investigated device is obtained by applying an external bias to the cell and measuring the generated photocurrent with a Keithley model 2400 digital source meter
and the data is
recorded as test report in the computer , as shown in figure (3.4).
Fig (3.4) : depicts the scheme of operation principles for Photovoltaic measurements system . 3.3 Deposition processes Techniques : In this section
,
the
deposition
processes
techniques which
employed for the manufacturing the thin films of OPSCs were
described . In the present work , Aerosol Assisted Chemical Vapor Deposition (AACVD) technique is applied to deposit TiO2 as compact layer in OPSCs. Spin Coating (SC) technique is used for deposition the scaffold perovskite layer of OPSCs . Hale transport layer of OPSCs was deposited
with the
techniques of
DC Sputtering Deposition
(DCSD) or Spray Deposition (SD) . For the counter electrode , thin film of Al deposited on top HTL by a Thermal Evaporation (TE) technique . 3.3.1 Aerosol Assisted Chemical Vapor Deposition technique : Aerosol Assisted Chemical Vapor Deposition (AACVD) technique is the process of deposition thin films from the vapor or fog of the liquid phase materials , by employing nebulizer (402Al), on preheated substrates . In this method , the thin films formed from the liquid media as the prepared precursor solution of TiO2 placed in cup of nebulizer (402Al), as shown in figure (3.5) , and atomized the solution to the fog or drops to the aerosol by using Ultrasonic frequencies (1.5MH) and sprayed manually on cleaned and preheated glass substrates at 400C in the fume hood . The thin film is formed after one hour of deposition time . The thin films obtained using AACVD have high adhesion with the substrates and smooth with small particle size , therefore this technique employed to deposit compact layer of TiO2 of all samples of OPSCs . The temperature of the coated substrates is monitored by an infrared temperature indicator, (-50 to1100)C, through all experimental runs, as shown in figure (3.6).
Fig (3.5): (a) depicted the image of the devices used in (AACVD) technique.(b) scheme of operation principles of US-nebulizer (402Al)
Fig (3.6) : depicted the image of the device IR Thermometer, AR872D, (-50 to 1100)C , Smart Sensor . 3.3.2 Spin Coating technique : In this deposition method, the thin films are deposited by dropping the prepared solution of desired material on substrate
placed on the
rotary disc moved with high spinning velocity as 2000 rpm for 30 sec by using Spin Coated System (KW4A) ,as shown in figure (3.7) followed by annealing the sample at the sintering temperature of thin film material. SC technique is suitable to the deposition of organic
thin films , therefore the preferred technique was SC to deposit the organic perovskite layer of OPSCs.
Fig (3.7) : depicted the image of the Spin Coated System (KW4A). 3.3.3 DC Sputtering Deposition : This is a very forward technique of deposition, in which target is held at high negative voltage and substrate may be at positive , ground or floating , potential see fig (3.8) .
Fig (3.8) Schematic layout atypical DC sputtering unit .
Substrates
may be simultaneously
heated or cooled or at room
temperature depending upon the requirement. Once the required base pressure is attained in the vacuum system of DC Sputtering Deposition System , usually argon gas is introduced at a pressure ≤ 0,1 torr. A visible glow is observed and current flows between anode and cathode, see I-V characteristic of plasma tube , indicating the deposition onset, as shown in figure (3.9a,b). When sufficiently high voltage is applied between anode and cathode with a gas in it, a glow discharge is set up with different following regions , as shown in figure (3-9c) [88]: i.
Cathode or Crooks dark space
ii.
Negative space glow
iii.
Faradays dark space
iv.
Positive column
v.
Anode dark space
vi.
Anode glow
Fig(3.9) (a) . Generation of Plasma by applying high voltage between two electrodes in an evacuated glass tube .(b). Typical I-V characteristic of Plasma. (c). Different regions of Plasma[88] .
These regions are the result of Plasma , i.e. a mixture electrons , ions, neutrals and photons released in various collisions . The density of various particles and the length over which they are spread and distributed depend upon the gas pressure .Energetic electron impacts case gas ionization .Ratio of ions/neutrals can be typical ≈ 10-4 . Thus at few milli Torr (m Torr) pressure , sufficiently large number of ions are generated that can be used to sputter the target . 3.3.4 Thermal Evaporation Deposition : The Thermal
Evaporation
Deposition
(TED)
technique
focusing on evaporation of target material in vacuum system, as shown in figure (3-10). The objective of this deposition process is to controllably transfer atoms from a heated source to a substrate located a distance away, where film formation and growth proceed atomistically . Quite simply, thermal energy is imparted to atoms in a liquid or solid source such that their temperature is raised to the point where they either efficiently evaporate or sublime. In TED technique we used to heat sources for the efficient evaporation of the target
material
electrically , the widely used resistance heating methods. The first sources used to heat evaporating relied on the Joule heating of metal filaments. Clearly, such heaters must reach the temperature of the evaporating in question while having a negligible vapor pressure in comparison to the source material .
Fig (3.10) Schematic layout atypical TED unit . Ideally, they should not contaminate, react with, or alloy with the evaporant, or release gases such as oxygen, nitrogen, or hydrogen at the evaporation temperature. These
requirements have led to the
development and use of resistance-heated
evaporation sources used
singly or with inert oxide or ceramic-compound crucibles. The most of crucible source consists of a tungsten wire resistance heater in the form of a conical basket that is encased in A12O3 to form an integral crucibleheater assembly. 3.4 Fabrication of Organic Perovskite Solar Cells devices : 3.4.1 Introduction : This section presents the description of the procedure implemented in our research for the manufacturing
the Organo-lead halide
Peroveskite Solar Cells (OPSC). At first, the synthesis organo-lead halide peroveskite materials MAPb(BrxI1−x)3−yCly at (x or y = 0,1, and 2) which employed as absorption layer in OPSCs were descried. The
testing for peroveskite materials which used for preparation OPSCs were described by studying the optical properties from the measurements of the absorbance spectrum in order to calculate the energy gap. X-ray diffraction, AFM microscope and SEM microscope were used in present work to study the structure of the samples. Finally, the tests OPSCs by Light I-V Measurement System were implemented in order to obtained the parameters of the manufacturing devices as shown in the schematic diagram for OPSCs, OIPSCs and FLPSCs in the figure 3.11.
Fig. 3.11:schematic diagram for OPSCs , OIPSCs and FLPSCs.
3.4.2 Synthesis of Organic Perovskite Materials : Synthesis of Organic Perovskite Materials (OPM) reported in Ref [89-93]. Methylamine Iodide (CH3NH3I) is
prepared by reacting
Methylamine, 33% of weight in Ethanol (BDH-LTD), with Hydro-Iodic acid (HI) 57% of weight in water (BDH-LTD) under ice bath stirring for 2 h. Typical quantities employed are 24 ml of Methylamine, 10 ml of HI, and 100 mL of Ethanol. Upon drying at 100 °C, a white powder is formed, which is placed overnight in a vacuum oven before use. Methylamine Bromide is prepared at the same method and previous quantities. To obtain the perovskite solution precursor , we dissolved both the CH3NH3I and the PbI2 (BDH-LTD) in
anhydrous N,N-
DiMethylFormamide (DMF) (Sigma Aldrich) at a 3:1 molar
ratio ,
such as in the table (3.2) and figure (3.12) ,with final concentrations of 40% of weight . 10 ml of solution preparation added to 0.15 g of Nano particle> 30 nm of Al2O3 powder
(China of origin) to obtain
scaffold peroveskite
precursor solution of CH3NH3PbI3. The reacting quantities of other samples of organo-lead halide pervskite solution precursors of CH3NH3PbX3 are inserted in the table (3-2). PbBr2 and PbCl2 in the table(3-2) are respectively.
supplied The
scaffold
of (OSAKA-LTD) and (BDH-LTD), peroveskite
precursor
solutions
of
CH3NH3PbX3, X is any halide or mixed of I , Br or Cl, are prepared with the same procedure of preparation the scaffold peroveskite precursor solution of CH3NH3PbI3 .
Fig(3-12) depicted the precursor solutions of CH3NH3PbICl2 , CH3NH3PbIBr2 , PbI2 and CH3NH3I. Table (3-2) explains the 3/1 Molar ratio of mixing compounds amounts of CH3NH3X/PbX2 Perovskite
CH3NH3I CH3NH3Br
Compounds
(g)
CH3NH3PbI3
0.158
CH3NH3IPbBr2
0.158
CH3NH3IPbCl2
0.158
(g)
PbI2
PbBr2
PbCl2
(g)
(g)
(g)
0.153 0.122 0.092
CH3NH3PbBr3
0.111
CH3NH3BrPbI2
0.111
CH3NH3BrPbCl2
0.111
0.122 0.153 0.092
3.4.3 Cleaning the substrates : To study the structural properties of OPSCs layers the glass slides substrates
were used, while
for optical properties quartz
slides
substrates
were used. The substrates were cleaned by water, pure
ethanol
and then cleaned by ultrasonic path
for
5
min before
preparation the samples. 3.4.4 Fabrication of Organic Perovskite Solar Cells : TiO2 compact layer preparation is a first fabricated applying Aerosol Assisted Chemical Vapor Deposition (AACVD) technique [73] by using Ultrasonic Atomizer (402AI) with ultrasonic frequency (1.5MHz). The precursor solution, which preparation of Nano particle> 20 nm of TiO2 powder (China of origin) dispersed in ethanol solvent by ultrasonic frequency, is sprayed on per-heated
Transparent Conductive Oxide
(TCO) glass substrates of Fluorine-doped Tin Oxide (FTO) (Coated Sodaline float glass of Visiontek, sheet Resistance 8 Ω/□ ) at 450o C , as shown in figure (3.13). FTO glass substrates are cleaned by acetone and iso-propanol under sonication for 5min before used.
Fig(3.13) depicted the image of the Ultrasonic Atomizer (402AI) is sprayed precursor solution of TiO2 on (FTO)
per-heated
glass
substrates . Deposited time is 1h and the substrates are left to cold at room temperature, followed by, depositing scaffold peroveskite precursor solution of CH3NH3PbX3 by spin coated technique at speed 2000 rpm at
30 sec time and annealing at 1500C
to obtain 6 samples of
(FTO/Compact TiO2/ScaffoldCH3NH3PbX3) as shown in the table (3.2).
Figure (3.14) is depicted the depositing peroveskite precursor solutions of
process
of the scaffold
CH3NH3PbX3 by
spin coated
technique. The temperature of the (FTO/Compact TiO2) coated substrates is monitored by an Infrared Thermometer of temperature indicator through all experimental runs.
Fig (3.14) depicted the depositing of the scaffold peroveskite precursor solution of CH3NH3PbX3 by spin coated technique[48]. CuI
thin
films
are
deposited
onto
(FTO/Compact
TiO2/ScaffoldCH3NH3X3) as a Hole Transport Layer (HTL) at room temperature by sputtering of pure CuI target in argon gas using DC sputtering
technique.
CuI target prepared by pressed CuI powder,
which supplied of (RIEDEL-DE-HANAG, Germany , 99.99 % pure), in disc with 50 mm diameter and 3 mm thickness is used for sputtering. The sputter chamber is evacuated by employing diffusion pump and rotary pump combination to achieve base pressure of 3.5 × 10-5 mbar . Argon of 99.99 % purity is used as reactive and sputtering working pressure of gases of 3.5 × 10-1 mbar for deposition of the films . The argon gas flow average is 240 Sccm, the 1.8 kV voltage is supplied to the sputter target using DC power supply, the discharge current of sputtering is 18 mA, the time of sputtering target is 1 h and active electrode spacing is 4cm. For the counter electrode, 100nm-thin film of
Al deposited on top HTL by a thermal evaporation technique, where Al evaporated under 10-5 mbar vacuum condition, to obtain 6 samples of OPSCs devices as shown figure (3.15).
Fig (3.15) inset depicts schematic 6 samples of OPSCs have different perovskite materials.
3.5 Fabrication of Organic-Inorganic Perovskite Solar Cells devices: 3.5.1 Introduction : In this section of experiment, Methyl amen Iodide lead Perovskite Solar
Cells
which
employed
Inorganic
perovskite
materials,
CsPbIxBryCl3-(x+y), as Hole Transport Layer (HTL) are fabricated. XRD patterns
of
CsPbIxBryCl3-(x+y) compounds are studied for perovskite
Structure samples at ( x = 0,1 , y = 0,1,2 ). The surface morphology of the films have been observed using Scanning Electron
Microscope
(SEM) and Atomic Force Microscope (AFM). Light I-V measurement test
reports are recorded by Integrated cell tester included I-V
Photovoltaic measurements system and Solar simulator. Measurements are tested at AM1.5 global sunlight (100 mW cm−2) .
3.5.2 Fabrication processes of solar cells devices : Synthesis of sensitizer Organic Perovskite Material ( OPM ) CH3NH3PbI3 reported in Ref [89] and mention in the experimental section (3.4.2). Synthesis Inorganic Perovskite Material (IPM) of CsPbIxBryCl3-(x+y) as HTL in OPSC. Pure CsPbCl3 (x=y=0) compound is achieved by heating un equal molar of stoichiometric mixture of CsCl (BDH-LTD) and PbCl2 in an evacuated Pyrex tube, (to 10-2mbar), at 501oC for 30 min, followed by quenching to room temperature, the samples as shown in figure (3-16).
The powders (100 mg) are dissolved/dispersed in
anhydrous polar organic solvents (1.5 ml) of (DMF). For I and Br doping, the appropriate weight ratios of CsPbIxBryCl3-(x+y)
samples
are shown as the table(3.3) and figure (3-16) .
a
b
c
Fig (3.16) (a) depicted CsPbIxBryCl3-(x+y) powder in an evacuated Pyrex tube after heating (b) after milling (c) after solving in DMF.
Table (3.3) explains the Molar ratio of mixing compounds amounts. Molar
Samples
rate
CsI
CsCl
PbBr2
PbCl2
(g)
(g)
(g)
(g)
x=y=0
CsPbCl3
1.683
x=1,y=0
CsPbICl2
2.598
x=1,y=2
CsPbIBr2
2.598
x=0,y=2 CsPbClBr2 x=y=1
CsPbIBrCl
CsPbIxBryCl3-(x+y)
2.781 2.781 3.67
1.683 2.598
3.67 1.835
1.39
powders are stirred in the same polar organic
solvents as DMF and sprayed manual as a hole transport layer on Al2O3 scaffold perovskite layer to obtain 5 samples of OIPSC as shown in figure (3.17) . For the counter electrode, 100nm-thin film of Al deposited on top HTL by a TED technique .
Fig (3.17) (a) inset depicts schematic 5 samples of OIPSCs have different materials of HTL(b) depicted the images of preparation steps of OIPSC which employed CsPbCl3 as HTL .
3.6 Fabrication of Free Lead halide Peroveskite Solar Cells : 3.6.1 Fabrication processes of devices : Methylamine Iodide and Bromide ((CH3NH3I) and (CH3NH3Br)) were prepared as reported in the previous section of 3.4.2 Synthesis of (OPM) and reported in Ref [89]. In this section, Lead composites are replaced with Tin composites to obtain safety materials and avoid the toxic harmful of Lead composites.
Both the CH3NH3I and the
anhydrous SnCl2 (BDH-LTD) are dissolved in
anhydrous N,N-
DiMethylFormamide (DMF) (Sigma Aldrich) at a 3:1 molar
ratio,
such as in the table (3.4) ,with final concentrations 40% of weight. Table (3.4) explains the Molar ratio of mixing compounds amounts. Perovskite
CH3NH3I CH3NH3Br
Compounds
(g)
CH3NH3ISnCl2
0.158
CH3NH3BrSnCl2
(g)
SnCl2 (g) 0.632
0.111
0.632
10 ml of solution preparation added to 0.15 g of Nano particle> 30 nm of Al2O3 powder (China of origin) to obtain scaffold peroveskite precursor solution of MAISnCl2. The reacting quantities of MABrSnCl2 was inserted in the table (3.4). The scaffold peroveskite precursor solutions of MABrSnCl2 was prepared with the same procedure of preparation
the scaffold
peroveskite
precursor
solution
of
MAISnCl2. TiO2
compact layer preparation on FTO substrates is a first
fabricated applying Aerosol Assisted Chemical Vapor Deposition (AACVD) technique as reported in the previous section fabrication of (OPSCs) devices and ref [73].
3.4.4 of
Followed by, depositing scaffold peroveskite precursor solution of MAISnCl2 or MABrSnCl2 by one step spin coated process at speed 2000 rpm and annealing at 1500 C
to obtain 2 samples of
(FTO/Compact TiO2/ScaffoldCH3NH3PbX3) , X is mix of any halide (I or Br with Cl), as shown in the figure (3.18) and the table (3.4).
Fig. (3.18) depicts schematic 2 samples of FLPSCs. CuI
thin
films
are
deposited
onto
(FTO/Compact
TiO2/ScaffoldMASnX3) as a Hole Transport Layer (HTL) at room temperature using DC sputtering technique as reported in section 3.4.4 of fabrication of (OPSCs) devices. Al
electrode
deposited on top HTL by a thermal evaporation
technique, which reported in section 3.4.4 of fabrication of (OPSCs) devices, to obtain tow samples of FLPSCs devices with strictures (FTO/Compact TiO2/ScaffoldMASnX3/CuI /Al electrode), as shown in figure (3.18).
Chapter four
Results and Discussions of OPSC
Results and Discussions of OIPSC
Results and Discussions of FLPSCs
4.1 Introduction : This chapter
includes
the
results
and
discussion of the
experimental measurements of the devices OPSCs, OIPSCs, FLPSCs and layers or thin films which formed these devices upon characterization
such as
structural, morphological and optical
properties. I-V Characteristic measurements of all fabricated devices will also discussed in the following articles. 4.2Results and Discussions of OPSCs: 4.2.1Structure properties : Figure 4.1(a) depicts the XRD pattern of CH3NH3PbI3 layer (red line) and XRD pattern of CH3NH3IPbCl2 layer (blue line), which achieved by deposited perovskite precursor solution using spin coating at speed 2000 rpm for 30 sec time and annealing at 150 0C. All reflections is indicated to the tetragonal CH3NH3PbI3. Reflections positions (black lines) of (002), (110), (200), (202), (004), (220), and (224) corresponding with tetragonal structure Space group I4/mcm (Z=4), a=8.800 Å,c=12.685 Å are indicated by ref [78,79] for comparative. XRD patterns of
the mixed halide
perovskite structure of
CH3NH3PbICl2 sample annealed at 150 0C is exhibited the tetragonal CH3NH3PbI3 phase and can be confirmed by reflections positions of (110) and (220) [29,81] . Figure4.1(b) depicts the XRD patterns of CH3NH3PbBr3 layer (red line) and CH3NH3IPbBr2
layer (green line)
which achieved
by
deposited perovskite precursor solution using spin coating at speed 2000 rpm for 30 sec time and annealing at 150 0C. Reflections positions (black lines) of (100), (110), (111), (200), (210), (211), (220), (300), (310), (222), (320) and (221) corresponding with cubic structure of CH3NH3PbBr3 are indicated by ref [80] for comparative.
4E+2
2E+4 1E+3
5E+3
CH3NH3PbBr3
CH NH PbI
CH3NH3PbBr3 Reff 4E+3
(100)
I (C PS)
(210)
0
0 0
20
40
60
(222) (320) (321)
40
(310)
(111)
(211)
4E+3
(220)
4E+1 1E+3
80
4E+2
(300)
(110)
2E+3
1E+2
0
0
2E+2
0
0 10
80
20
30
40
50
60
(deg)
(deg)
(a)
(b)
2000
1.2E+2
2E+2
CH3NH3BrPbCl2
CH3NH3PbBr3 [12]
1.6E+3
CH3NH3PbBr3[12]
CH3NH3PbI3 [10]
1600
1.6E+2
CH3NH3BrPbI2 80
1.2E+3
8E+2
80
(110)
800
I (CPS)
I (CPS)
(220)
(100)
I (CPS)
I (CPS)
1.2E+2
(110)
1200
0
0 20
40
60
(deg)
80
(210)
(200)
4E+2
40
(111)
40
(100)
400
0
0
0 10
20
30
40
50
(c)
8E+2
6E+2
(200)
I (C PS)
I (C PS)
8E+3
1.2E+2
CH3NH3IPbBr2
3E+3
8E+1
(224)
(200)
2E+2
(202) (004) (220)
(002) (110)
3E+2
I (C PS)
1E+2 3 3 3 ____ CH NH PbI Ref 3 3 3 ____ CH NH I PbCl 1E+4 3 3 2
(d)
Fig. 4.1 (a) XRD patterns of CH3NH3PbI3 and CH3NH3IPbCl2 layer on sheet glass substrates comparative with CH3NH3PbI3 Ref [78,79] . (b)XRD patterns of CH3NH3PbBr3 and CH3NH3IPbBr2 layer on sheet glass substrates samples comparative with CH3NH3PbBr3 Ref [80]. (c)XRD patterns of CH3NH3BrPbI2 layer on sheet glass substrate sample comparative with CH3NH3PbBr3 Ref [80] and CH3NH3PbI3 Ref [78,79]. (d)XRD patterns of CH3NH3BrPbCl2 layer on sheet glass substrate samples comparative with CH3NH3PbBr3 Ref [80].
60
The present results, XRD patterns of the halide perovskite structure of CH3NH3PbBr3 sample (red line) is exhibited the cubic CH3NH3PbBr3 phase at the reflections positions (black lines) of (100), (110), (111), (200), (211) and (300) [80] . XRD patterns of
the
mixed
halide
perovskite structure of
CH3NH3PbIBr2 sample (green line) is exhibited
the
cubic
CH3NH3PbBr3 phase at the reflections positions (black lines) of (100), (110), (111), (200) , (210) and (300) [80] as shown in figure 4.1(b) . However, the sample of CH3NH3BrPbI2 film is appeared maximum peak of XRD at reflection position (220) corresponding with tetragonal CH3NH3PbI3 structure which indicated by ref [78,79], as shown in figure 4.1(c) . XRD patterns of
the mixed halide
perovskite structure of
CH3NH3PbBrCl2 sample annealed at 150C is
exhibited
the cubic
CH3NH3PbBr3 phase and can be confirmed by reflections positions of (100) and (110) [80] , as shown in figure 4.1(d). The tolerance factor (t) is calculated using equation (2.10) to identify the distorted perovskite structure and inserted data in the table 4.1 , where RI=2.2A, RBr=1.96A, RCl=1.81A, RPb=1.19A, methyl-ammonium (CH3NH3+) with RA = 1.8A.
On the basis of tolerance factor values,
structure of CH3NH3PbI3 materials in the table 4.1 is tetragonal due to (0.8 ≤ 𝑡 ≤ 0.89) [74,75] and identical structure to the results of XRD pattern. The perovskite material of CH3NH3PbBr3 have cubic stricture in the table 4.1 as consequence of XRD results .The perovskite material of CH3NH3PbICl2 have tetragonal stricture in the table 4.1 as
consequence
of
XRD results. The perovskite materials of
CH3NH3IPbBr2 and CH3NH3BrPbCl2 compounds have cubic structure due to (0.9 ≤ 𝑡 ≤ 1) [74,75] and identical structure to the results of
XRD pattern. The perovskite material of CH3NH3BrPbI2in the table 4.1 have tetragonal structure as consequence of XRD results . Figure 4.2(a) depicts AFM 3D-images of compact layer of TiO2 on FTO electrode deposited by (AACVD) technique on preheated sheet glass substrate at 450 0C temperature and deposited at 1h time .
ab
c Fig. 4.2(a) AFM 3D-image of compact layer of TiO2 on FTO electrode. (b)chart plot of grain size percentage distribution (c) vertical 2D-image on compact layer of TiO2 on FTO electrode . Figure 4.2(b) depicts chart plot of grain size percentage and explains Gaussian
distribution of
the grain size of particles of the surface
topography of TiO2 layer. Surface compact TiO2 layer have Average Diameter (D = 89.11 nm), Peak–Peak of the surface (PP = 66.9 nm), Root Mean Square (RMS = 18.2nm) and Roughness Average (RA = 15.9 nm) as shown in the figure4.2(c). The data of AFM images are confirmed by SEM images of TiO2 compact layer on FTO substrate which scanned using a magnification 30kx and high voltage 20kV, as
shown in
figure.(4.3), then ( x=46.88nm, y=53.33nm and
D=71nm).
Fig (4.3).Top SEM images of compact layer of TiO2 on FTO electrode. Scale bar of left image is 500nm and right image is 1µm . Figure4.4 (a) is illustrated top SEM image of CH3NH3PbI3 film , (b) Top SEM image of CH3NH3PbBrI2 film, (c) Top SEM image of CH3NH3PbICl2 film and (d) Top SEM image of CH3NH3PbBr3 film, (e) Top SEM image of CH3NH3PbIBr2 layer. (f) Top SEM image of CH3NH3PbBrCl2 layer, scale bars of the images are 5µm, scanning with high voltage 5kV and magnification 10 kx. Samples are prepared by deposited perovskite precursor solution using spin coated at speed 2000 rpm at 30 sec time and annealing at 150 0C.
Fig. 4.4 (a) Top SEM image of CH3NH3PbI3 layer. (b)Top SEM image
of
CH3NH3BrPbI2
layer.
(c)
Top
SEM
image
of
CH3NH3IPbCl2 layer. (d) Top SEM image of CH3NH3PbBr3. (e) Top SEM image of CH3NH3IPbBr2 layer. (f) Top SEM image of CH3NH3BrPbCl2 layer. (g) is
top view of SEM image of
CH3NH3PbBr3 and (h) is top view of SEM image of CH3NH3PbI3 copy of ref [21] .
SEM image of CH3NH3PbICl2 film on glass substrate, figurer 4.4(c), is appeared more cubic shapes of crystals formations than other samples and SEM image of CH3NH3IPbBr2 film, figure 4.4(b), is appeared micro rod-shapes of crystals formations. The spherical shapes structures of figure 4.4(b) is appeared due to the precursor solution may be rich PbI2. It can be to observe that similarity of the shapes between the SEM images of figure 4.4(b) of CH3NH3BrPbI2 layer and SEM images of figure 4.4(e) of CH3NH3IPbBr2 layer that
have long micro rods
formations with up to 10μm. May be observe of SEM images of figure 4.4 (a) of CH3NH3PbI3 layer and SEM images of figure 4.4(d) of CH3NH3PbBr3 layer on glass substrates that have grain size of aggregations of islands formations of the films up to 1 μ m. Images of figure 4.4 (e and f) appear
more crystalline of
CH3NH3IPbBr2 and CH3NH3BrPbCl2 perovskite layer, respectively. The single crystal of images figure 4.4 (e and f) have 500 nm scale bar. In figure 4.4(g and h), the SEM of samples of CH3NH3PbBr3 and CH3NH3PbI3 of ref [21] are depicted, in comparison than present results. Single CH3NH3PbBr3 crystal with scale bar is 100 nm. In the case of the CH3NH3PbBr3, the shapes are more cubic formations than sample of the CH3NH3PbI3 [21]. 4.2.2 Optical properties : Figure 4.5(a) is explained the absorption of halide perovskite films and appears more absorption to CH3NH3PbI3 than other samples that which are measured in the wavelength range (400-800) nm using a (SPECTRO UV/VIS Double Beam (UVD-3500) Labomed, Inc.) and glass substrates as reference samples .
0.2
0.16
0.14
0.28
0.18
0.6
M AIPbBr2 M AIPbCl2 0.13
M APbBr3
0.17 0.5
M APbI3
0.14
M ABrPbCl2
0.26
0.18 0.13
M ABrPbI2
0.17
Abs
0.4 0.12 0.12
0.16 0.24
0.16
0.3 0.1 0.12
0.14
0.08
0.12
0.16
0.22
0.15
0.2 400
500
600
700
800
W ave length (nm)
(a) 6E+9
1.2E+10
6E+10 1.2E+10 6E+9
1.4E+9
Eg = 2.1 eV of CH NH PbBr 3
Eg = 1.8 eV of CH NH IPbBr 3 3 2
3
3
Eg = 1.56 eV of CH NH PbI
5E+9
3
3
3
Eg = 1.7 eV of CH NH Br PbI 3 3 2
Eg = 1.92 eV of CH NH Br PbCl 3 3 2 4E+9
8E+9
3E+9
6E+9
2 2 ( E * ) (eV /cm )
2 2 ( E * ) (eV /cm )
1E+10
1.3E+9
Eg = 1.9 eV of CH NH I PbCl 3 3 2
2E+9
2E+9
1E+9 1.2
1.6
2
2.4
2.8
3.2
E (eV)
5E+9
8E+9
4E+9
6E+9
3E+9
4E+9
2E+9
2E+9
1E+9
4E+10
1.2E+9
4E+9
1E+10
2E+10
1.1E+9
0 1.2
1.6
2
2.4
2.8
E (eV)
(b)(c) Fig. 4.5(a) depicts absorption of Visible light of the CH3NH3PbX3 films. (b) and (c) explain energy gap of the CH3NH3PbX3 films. Where X is (I ,Br ,Cl or mix of those halides )
3.2
Plots inset of (αhv)2 versus photon energy (hv) for peroveskite layers on glass substrates are illustrated in Figure 4.5(b and c). A direct optical band gap energy (Eg) for halide perovskites materials CH3NH3X3, (X = Cl, Br, I) is reported by Simon et al [76]. (Eg) of samples is determined by fitting the absorption data to the direct transition
equation (4). The optical band gap value is obtained by
extrapolating the linear part of the curve (αhv)2 as a function of photon energy, hv , intercept the (hv) axis at α = 0. The values estimated of Eg are inserted in table 4.1. It can be observed that increased energy gap with increased ,(x), the percentage of the Br in MAPb(BrxI1−x)3−yCly at y = 0, as shown in figure 4.6. Then MAPbBr3 and MAPbI3 films
are corresponding to the
optical band-gap value of (2.1 and 1.56) eV, respectively, as shown in the
table 4.1. When,
(y=2), an amount of
Cl in term
MAPb(BrxI1−x)3−yCly is existed, the changing in the energy gap
of
perovskite materials is very slight increasing or isn't appeared, as reported in [28], see figure (4-6), then energy gap is increased (from 1.9 to 1.92) eV at y = 2. Table (4.1) explains the structure and optical parameters of peroveskite materials. Perovskite
t
Structure
Compounds
Eg
a
c
(eV)
(Ao) (Ao)
CH3NH3PbI3
0.834
Tetragonal
1.56
6.23 6.28
CH3NH3IPbCl2
0.942
Tetragonal
1.9
5.91 5.94
CH3NH3PbBr3
0.844
Cubic
2.1
5.92 5.92
CH3NH3BrPbI2
0.784
Tetragonal
1.7
6.18 6.21
CH3NH3IPbBr2
0.897
Cubic
1.8
6.05 6.05
CH3NH3BrPbCl2
0.89
Cubic
1.92
5.76 5.76
2.2
2
Energy Gap (eV)
y=2
1.8
y=0
1.6
1.4 0
0.2
0.4
0.6
0.8
1
x of Br
Figure 4.6 is explained energy gap vs percentage of the Br in MAPb(BrxI1−x)3−yCly at y = 0,2 It can be observed that perovskite materials with cubic stricture have larger energy gap comparative to the distorted perovskite materials with tetragonal stricture, as shown in the table 4.1 and reported in [76]. 4.2.3 Parameters of OPSCs : I-V curve of Organolead iodide Peroviskite Solar Cell (OPSC) which employed ofMAPbI3 as absorption layer of photovoltaic device have best PCE and it is depicted in figure 4.7(a). Measurement is carried out under 1 sun illumination (AM1.5G,100 mW/cm−2), active area of solar cell is 0.1 cm2and sweeping voltages in the scan-direction with a scan rate of s = 50 mV/s. Figure 4.7(b) is depicted I-V curves of six devices of
OPSC-based on absorption layer materials (MAPbI3, MAIPbCl2,
MAPbBr3, MABrPbI2, MAIPbBr2 or MABrPbCl2). Measurements are
tested at the same conditions as the figure 4.7(a). The other Light I-V Measurements test reports are depicted in index A. 2
MAPbI3 MAPbBr3 1.6
MABrPbI2
P hoto cu rrent (m A )
MAIPbCl2 MAIPbBr2 1.2
MABrPbCl2
0.8
0.4
0 0
200
400
Photo Voltage (mV)
(a)
(b)
Fig 4.7(a). I-V curve of OPSC has CH3NH3PbI3 as absorption layer of device. (b)I-V curves of six devices of OPSC-based on six choices of absorption layer materials.
600
800
Table 4.2 explains parameters of I–V curve characteristics of OPSCs. Perovskite
PCE
Voc
Isc
FF
Rs
Rsh
Compounds
%
(mV)
(mA)
(Ω)
(Ω)
CH3NH3PbI3
2.15
595.9
1.39
0.25
262.7 232.59
CH3NH3PbBr3
0.74
614.3
0.29
0.41
214.9
6470
CH3NH3BrPbI2
0.56
553.7
0.24
0.43
505
10010
CH3NH3IPbCl2
0.27
569.4
0.12
0.36
833
14910
CH3NH3IPbBr2
0.12
266.3
0.183
0.25
1200
1880
CH3NH3BrPbCl2
0.07
541.9
0.058
0.22
12200 18710
All parameters of OPSCs are inserted in the table (4-2). The best (PCE = 2.15) is achieved to the OPSC employing CH3NH3PbI3as sensitizer due to the best optical properties ,highest absorption and lowest optical energy gap, of absorption layer CH3NH3PbI3, as shown in figure 4.7(a,b) and the table (4.2) .To shed light on figure 4.5(a) and figure 4.7(b) ,it can be observed that improved PCE of OPSC when increased absorption of perovskite layer of device . Figure (4.8) is explained the power conversion efficiency PCE of all photovoltaic devices of OPSCs
as function of all the parameters (R s,
Rsh, FF, Voc, and Isc) of all photovoltaic devices of OPSCs. The parameters
series
and shunt
resistances
( Rs and
Rsh )
determine the full factor value of solar cell device [71,72] ,so clear that increase the full factor values of photovoltaic devices when the difference between of Rs and Rsh values are increased , as shown in figure 4.8(a). The value of PCE of solar cell device depended of the open voltage circuit, Voc, and short current circuit, Isc, as in the equation (2-3). As consequence of observations, if the Voc and Isc values of
photovoltaic devices (OPSCs) are increased then PCE of photovoltaic devices is improved, as shown in the figure 4.8(b). 0
4000
8000
12000
16000
20000
Rsh ( ) 0
4000
8000
12000
16000
2.5
Rs (
)
2
PCE %
1.5
1
0.5
0 0.2
0.25
0.3
0.35
0.4
0.45
FF
(a)
(b)
Fig. 4-8(a) explains PCE of OPSCs as function of Rs and Rsh , (b) explains PCE of OPSCs as function of Voc and Isc. It can be observed that PCE of solar cells devices are decreased consequence to increase the percentage of the Br, (x), in MAPb(BrxI1−x)3−yCly at y = 0, as shown in figure 4.9. Then devices as absorption layers MAPbBr3 and MAPbI3 have PCE values of (2.15 and 0.74) % , respectively, as shown in the table 4.2. In addition, low PCE of device at (Br = 0.66%) is 0.12%. It can be observed that structure of peroveskite materials of absorption layer is influenced in performance ,PCE, of OPSCs devices. OPSC device with absorption layer of distorted perovskite structure, tetragonal at (x = 0), have higher efficiency (PCE) than OPSCs devices of absorption layer with cubic structure at (x= 1). At y = 2, an amount of Cl in term MAPb(BrxI1−x)3−yCly is existed, the changing in the PCE of devices is very slight decrease, see figure 4.9, then PCE of solar cells devices is decreased from (PCE= 0.27 to 0.07) % at (x = 0,1), respectively. As consequently,
increased PCE with tetragonal structure of perovskite material, at (x=0, y=2), of the absorption layer of OPSCs devices is observed. Decreased PCE with cubic structure of perovskite material, at (x=1, y=2), of the absorption layer of configuration OPSCs devices is observed.
2.5
2
PCE %
1.5
y=0 1
0.5
y=2 0 0
0.2
0.4
0.6
0.8
1
x of Br %
Figure 4-9is explained PCE vs percentage of the Br in MAPb(BrxI1−x)3−yCly at y = 0,2
4.2.4 Energy levels diagram of the Methyl-amine Lead Iodide PSC: The best efficiency of OPSCs was achieved with employed Methyl-amine Lead Iodide (CH3NH3PbI3) as absorption layer of solar cell device (FTO/ TiO2/CH3NH3PbI3/CuI /Al electrode ). The mechanism transport of carriers charges in this device is that shown in
figure (4-10), the absorption photon excites the valence electron of Valence Band (VB) of CH3NH3PbI3at level
energy (VB = 5.43eV)
[27] and the excited electron is transported to the Conduction Band at level energy (CB = 3.93 eV) [27]. At the same time ,the excited electron is leaved the hole in the (VB) of CH3NH3PbI3 at level (VB = 5.43eV). The excited electron at level (CB=3.93eV) of CH3NH3PbI3 was injected in to the Conduction Band of TiO2 at level (CB = 4.1eV) [15] and injected in to the Conduction Band of FTO at level (CB = 4.4eV) [94]. The hole in the (VB) of CH3NH3PbI3 at level (VB = 5.43eV) was
filled with the electron of Valence Band of CuI
at
level (VB = 5.4eV) [95,96] by injection process and leaved hole at level (VB = 5.4eV ) of
CuI
which
Conduction Band of Al electrode
filled with
the electron of
at level (CB = 4.3eV) [94] by
injection process too, as shown in figure (4.10). As consequence, the potential difference is generated between the FTO electrode and Al electrode of OPSC
due to the incident photons
absorption of
CH3NH3PbI3 layer and increment the density of electrons and holes of carriers charges at the FTO
and Al electrodes , respectively.
Therefore , any circuit connects with OPSC, the photo current flows in the out circuit. To shed light on the figure (3.10), it can to observe that the HTM of CuI is doing as a barrier potential between MAPbI3 layer and Al electrode and it is prevented the recombination of the generated photo-electrons and holes via Al electrode .
-2.00
CuI 2.3
TiO2
-4.00
CB
Energy (eV)
4.8
3.93
4.2
Al
Eg = 1.5 eV
4.2
FTO
5.43
5.4
CH3NH3PbI3
-6.00
VB
7.4
-8.00 Fig(4.10) Energy levels diagram of solar cell device (FTO/ TiO2/CH3NH3PbI3/CuI /Al electrode ).
4.2.5 Summary of results of OPSCs : In summary, the following results are observed that: 1. the OPSCs with configuration (FTO/TiO2/ (CH3NH3)PbX3 perovskite with Al2O3 scaffold /CuI/Al electrode)
have been
successfully fabricated. 2. Present experimental results demonstrated that an optimum efficiency of OPSCs, PCE = 2.15%,can be achieved by using CH3NH3PbI3 as sensitized absorption layer, harvester light layer, in OPSC . 3. Experimentally,
PCE is increased
when increased the
absorption and decreased band gap energy of pervskite layer of OPSCs . 4. Increased energy gap with increased the percentage of the Br in MAPb(BrxI1−x)3−yCly, proveskite materials, at y = 0. When the amount of Cl in term MAPb(BrxI1−x)3−yCly is existed, the changing in the energy gap of perovskite materials is very slight increasing or isn't appeared, then energy gap is increased (1.9 to 1.92) at y = 2. 5. The perovskite materials
with
cubic structure
have
large
optical energy gap caused that lower PCE of OPSCs devices in comparison
to
the distorted perovskite materials
with
tetragonal structure, high absorption caused that increased PCE of OPSCs devices. 6. In OPSCs, the doing of layer of CuI
is barrier potential
between MAPbI3 layer and Al electrode and it is prevented the recombination of the generated photo-electrons and holes via Al electrode .
4.3Results and Discussions of (OIPSCs) devices : 4.3.1Structure properties : Figure 4.11(a) depicts the XRD pattern of synthesis CH3NH3PbI3 layer, which achieved by deposited CH3NH3PbI3 precursor solution, spray manually, on preheated glass sheet substrate at 100 0C.All reflections is indicated to the tetragonal CH3NH3PbI3. Reflections positions of (002), (110), (200), (202), (004), (220), and (224) corresponding with tetragonal structure Space group I4/mcm (Z=4), a=8.800 Å, c=12.685 Å are indicated by [29,81] and our calculation is a=6.23 Å, c =6.28 Å. Figure 4-11(b) shows the XRD pattern of 5 samples of CsPbIxBryCl3(x+y)
compounds, measurements are tested as powder samples.
400 C sC lP bB r2 C sIPbC l2
CH NH PbI
(002) (110)
____
C sIPbB r2 C sP bC l3 C sP b IB rC l A ST M (C sPbC l3)
80
(224)
I (C PS)
(202) (004) (220)
200
120
______
(200)
I (C PS)
300
3 3 3 CH NH PbI 3 3 3
40 100
(100)
(101)
(002)
(112) (201)
(202)
(301)
0
0 0
20
40
(deg)
A
60
80
0
20
40
60
80
(deg)
B
Fig. 4.11: (a) explains XRD pattern of CH3NH3PbI3 layer on sheet glass substrate . Red curve is present work, black lines represent Ref [29,81]. (b)XRD patterns of CsPbIxBryCl3-(x+y)
powder samples
represent with colored curves .black lines represent JCPDS(18-0366) Ref .
All reflections of X-ray diffraction patterns of CsPbCl3 compound , x = y = 0 , corresponding with JCPDS(18-0366) Ref as in an appendix B, which indicated to the cubic perovskite structure , a = 5.605A ,SG. P4mm. Calculations of the tolerance factor (t) from equation (2-6) to identify the distorted perovskite structure were inserted in the table 4-3, where RI=2.2A, RBr=1.96A ,RCl=1.81A ,RPb=1.19A, RCs=2.35A, methylammonium(CH3NH3+) with RA = 0.18 nm [75]. Structure of CsPbCl3 compound in the table 3.3 is identical to the results of XRD pattern of JCPDS(18-0366)Ref. CsPbIxBryCl3-(x+y) compounds
have
cubic
Structure at ( x = 0 , y = 0, 2) due to (0.9 ≤ 𝑡 ≤ 1) and have hexagonal at ( x = 1 , y = 0,1, 2 ) due to (𝑡 ≤ 1) as shown in the table 4.3. All structure parameters as results of XRD patterns of CsPbIxBryCl3-(x+y) compounds are inserted in the table 4-3. Figure4.14(a) depicts AFM 3D-images of compact layer of TiO2 deposited by (AACVD) technique on preheated sheet glass substrate at 4500C temperature and deposited at 1h time . Figure 4.12(b) explains chart plot of grain size percentage, the histogram of chart plot with Gaussian distribution of grain size of the particles of the surface topography of TiO2 layer. Surface compact TiO2 layer have Average Diameter (D = 150.11 nm), Peak–Peak of the surface (PP = 23.3 nm) , Root Mean Square (RMS = 5.65nm) and Roughness Average (RA = 4.87 nm) as shown in the figure4.12(c).
A
b
c Fig. 4-12(a) AFM 3D-image of compact layer of TiO2.(b)chart plot of grain size percentage distribution and (c) vertical 2D-image on compact layer of TiO2. Figure 4.13 (a) shows top SEM images of CH3NH3PbI3 layer scanning with high voltage 5kv and magnification (5)kx, deposited by spray manually of CH3NH3PbI3 precursor solution on sheet glass substrate and annealing at 150 0C. CH3NH3PbI3 image with 10μm scale bar explains the aggregation of materials to the islands formations.
Figure 4.13 (b) shows top SEM images of inorganic perovskite images
of CsPbCl3
layer scanning with high voltage 5kV and
magnification (5)kx, deposited by spray manually of CsPbCl3 precursor solution on preheated sheet glass substrate at 100 0C.SEM image with scale bar 10μm depicts micro particles aggregation
of inorganic
composite of CsPbCl3. The data of SEM images of TiO2 compact layer deposited by (AACVD) technique on FTO substrate which scanned using a magnification 30kxandhigh voltage 20kVas shown in Figure 4-13(c), then ( x=23.44nm, y=33.33nm and D=40.75nm). Figure 4.13(d)depicts the top SEM image of inorganic perovskite layer ofCsIpbCl2which scanned using a magnification 60kxwith high voltage 20kV. The sample deposited by spray manually of CsIpbCl2 precursor solution on preheated sheet glass substrate at 100 0C.the SEM images with 500nm scale bar appeared sheets formations of CsIpbCl2 material. In the XRD results and according to the tolerance factor, CsIpbCl2material have hexagonal
structure
as shown in the table
4.3.Figure 4.13(e) depicts top SEM image of CsClPbBr2 which scanned using a magnification60kx with high voltage 20kV,then (x=128.9nm, y=136.7nm and D=187.9nm). The sample deposited by spray manually of CsClPbBr2 precursor solution on preheated sheet glass substrate at 100 0C. SEM image appeared crystals shapes as shown in the Figure 4.13(e) , scale bars of inorganic perovskite images are 500nm. In the XRD results and according to the tolerance factor, CsClPbBr2 material have cubic structure as shown in the table 4.3.
Fig. 4-13 (a).Top SEM images of CH3NH3PbI3 layer.(b). Top SEM images of CsPbCl3 layer. scale bars of perovskite images are 10µm. (c). Top SEM images of compact layer of TiO2, scale bar of image of TiO2 is 500nm,(d). Top SEM images of CsIPbcl2 layer,(e). Top SEM images of CsClPbBr2 layer,
scale bars of left perovskite
images are 500nm. SEM images of inorganic samples tested with magnification and high scan voltage corresponding to the resolution of the SEM images of
the specimens therefore it differed from the magnification and high scan voltage of organic samples .The data of AFM images are confirmed by SEM images of TiO2 compact layer on FTO substrate as shown in Figure 4.13 (c), then ( x=23.44nm, y=33.33nm and D=40.75nm) .
4.3.2 Optical properties of inorganic HTM : The absorption of inorganic halide perovskite films are explained in figure 4.14a and appeared less absorption to CsPbCl3 film than other samples that which are measured in the wavelength range (400-800) nm using a (SPECTRO UV/VIS Double Beam (UVD-3500) Labomed, Inc.) and glass substrates as reference samples . Plots inset of (αhv)2 versus
photon
energy (hv) for inorganic
halide peroveskite layers on glass substrates are illustrated in figure 4-14(b and c). Yuan Ye et al are reported that the direct optical band gap energy values for cesium lead halide perovskites materials CsPbX3, when (X = I, Br and Cl),
Eg = 1.35,1.76 and 2.17(eV), respectively
[97]. For CsPbX3, (X = I, Br or Cl), likely resulting to the small hole effective mass and thus large mobility of the hole of the perovskite solar cell [97], therefore the CsPbX3 peroveskite materials are employed as HTM of the peroveskite solar cells in the present work. In our results, (Eg) of samples is determined by fitting the absorption data to the direct transition equation (2.4). The optical band gap value is obtained by
extrapolating the linear part of the curve (αhv)2 as a
function of photon energy, hv, intercept the (hv) axis at α = 0. The values estimated of Eg are inserted in table 4.3.
0.34
0.39
0.22 0.37
0.38
CsIPbCl2
0.34
0.39
CsCl PbBr2 0.36
CsPbCl3
0.37
CsIPbBr2 CsPbIBrCl
0.36
Abs
0.21
0.33
0.38
0.36 0.33
0.38 0.35
0.2
0.35 0.32
0.38 0.35
0.34 0.32
0.37
0.19 0.34
0.33
400
500
600
700
800
W ave length (nm )
(a) 4E+11 2.4E+11
4E+10
2.8E+11
1E+11
CsIPbBr2, Eg = 1.6 eV CsPbCl3, Eg = 2 eV
CsPbIBrCl , Eg = 1.78 eV
2E+11
CsIPbCl2 , Eg = 1.7 eV
3E+11
1.6E+11
2E+10
2
2E+11 1.2E+11
1E+10
(hv* ) (eV /cm )
2
( *hv) (eV /cm )
2
2
3E+10
2.4E+11
CsClPbBr2, Eg = 1.9 eV
8E+10
2E+11 6E+10 1.6E+11
4E+10
1E+11 8E+10
0
0 1.2
1.6
2
2.4
2.8
3.2
4E+10
1.2E+11
8E+10
2E+10 1.2
1.6
E ( eV)
(b)
2
2.4
E (eV)
(c)
Fig. 4.14(a)depicts absorption of Visible light of theCsPbX3films.(b) and (c) explain energy gap of theCsPbX3films. Where X is (I ,Br ,Cl or mix of those halides).
2.8
3.2
Table (4.3) explains the optical properties and structure parameters of compounds materials of OIPSCs. HTM of
Eg of HTM
Tolerance
Structure
a (A)
c (A)
OIPSCs
(eV)
factor (t)
CsIPbBr2
1.6
1.02
Hexagonal
5.84
7.99
CsIPbBrCl
1.78
1.04
Hexagonal
5.66
6.96
CsIPbCl2
1.7
1.07
Hexagonal
5.55
6.88
CsClPbBr2
1.9
0.933
Cubic
5.71
5.71
CsPbCl3
2
0.980
Cubic
5.60
5.60
CH3NH3PbI3
1.56
0.834
Tetragonal
6.23
6.28
Thus, the inorganic
composed of cesium lead chloride,CsPbCl 3,
peroveskite material have energy gap, Eg = 2eV, which confirmed with the energy gap value reported of ref [97], (Eg = 2.1eV), as shown in the table (4-3) and the figure 4-14b. Hence, the inorganic composites of cesium lead halide peroveskite HTM with cubic structure have larger energy gap than HTM have distorted peroveskite structure, Hexagonal structure, as shown in the table (4-3)and the figure 4.14. In addition, the in organic composites of cesium lead mix halide (I and Br) peroveskite HTM have higher absorbency and lower energy gap than cesium lead chloride composites (CsPbClX2), X = I or Br or Cl, as shown in the table (4-3) and the figure 4.14. 4.3.3 Parameters of OIPSCs : I-V curve of OIPSC which have CsPbCl3 as HTL device is depicted in the figure 4.15(a). Measurements are carried out under 1 sun illumination (AM1.5G,100 mW/cm−2), active area of solar cell is 0.1 cm2 and sweeping voltages in the scan direction with a scan rate of s = 50 mV/s. Figure 4.17(b) explains I-V curves of five OIPSC-based
devices which have hole transport
materials CsIPbBr2, CsClPbBr2,
CsPbCl3, CsIPbCl2 and CsIPbBrCl. Measurements are tested
at the
same conditions as the figure 4.15(a). All parameters of OIPSCs inserted in the table (4.4). The test reports of other devices are depicted in an index A. 2
CsIPbBr2 CsClPbBr2 1.6
CsPbCl3
P h o to cu rren t (m A )
CsIPbCl2 CsIPbBrCl 1.2
0.8
0.4
0 0
200
400
600
Photo Voltage (mV)
(a)
(b)
Fig 4-15(a). I-V curve of OIPSC has CsPbCl3 as HTL device.(b) I-V curves of five devices of OIPSC-based on hale transport materials.
800
Table 4.4 explains parameters of
I–V curve characteristics of
OIPSCs. HTM
of PCE
Voc
Isc
FF
Rs
Rsh
(Ω)
(Ω)
OIPSC
%
(mV)
(mA)
CsIPbBr2
0.81
472.9
0.808
0.21
550
250
CsIPbBrCl
0.72
551.2
0.32
0.40
400
3000
CsIPbCl2
0.21
474.8
0.148
0.29
1010
5010
CsClPbBr2
1.02
435.5
1.21
0.19
125.9 214.3
CsPbCl3
1.45
640
1.006
0.22
616.6 628.44
The best PCE ( PCE> 1 ) is achieved to the OIPSC devices which have cubic structure of perovskite CsPbCl3 and CsClPbBr2 as HTL when Rs and Rsh of these devices less than 1kΩ , as shown in the table (4.4) . For the hexagonal structure of perovskite materials of (HTL) of OIPSC
devices',
( PCE < 1 ) is achieved, as shown in the table
(4.3) and the table (4.4). In addition, the absorption of cesium lead halide peroveskite of HTM have the contrary influence of power conversion efficiency of photovoltaic devices, OIPSCs. If absorption of HTM of devices are increased then PCE of these devices are decreased probably caused to prevent the absorption of the harvester light layer of OIPSCs devices, CH3NH3PbI3 layer. To shed light on the tables (4.3) and (4.4) , when we inserted PbBr2 instead of PbCl2 of CsPbCl3 compound , it can to observe that the short current of the solar cell (Ish) is increased ,the open voltage circuit (Voc) and PCE of the solar cell
are decreased, may be, due to the
transformation of cubic perovskite structure to the distorted cubic perovskite structure in HTL. Consequently, the distorted of perovskite structure of HTL is influencing the PCE of OIPSC. There for , PCE
is increased when the value of the tolerance factor (t) of perovskite structure of the hole transport materials in OIPSC is closer to unity, approximately. When t occurs in the narrow range of 0.89-1.0,at the cubic crystal structures, the inorganic cesium lead halide perovskite materials are likely obtained high-efficiency of perovskite HTM based Meso-pores Solar Cells, due to the HTM perovskite compounds featuring large band gaps and low absorbance ,as report in ref [98-105]. Consequently, transparent HTM is allowed to enhance
or
improve the photons
absorption in the harvester light layer, CH3NH3PbI3 layer, of OIPSCs devices caused to increase PCE of OIPSCs devices.
4.3.4Summary of results of OIPSCs :: In summary, the following results were observed that: 1. In OIPSCs,
the distorted perovskite
structure
of
HTL is
influencing the PCE of OIPSC devices and values Rs and Rsh of these devices. 2. Inorganic composites of cesium lead chloride, CsPbCl 3, peroveskite material have energy gap, confirmed
Eg = 2eV, which
with the energy gap value reported of ref [97],
(Eg= 2.1 eV). 3. Experimentally,
inorganic composites of cesium lead halide
peroveskite HTM with cubic structure have larger energy gap than HTM have distorted peroveskite
structure , Hexagonal
structure. 4. Empirically , inorganic composites of cesium lead mix halide (I and Br) peroveskite HTM have higher absorbency and lower energy gap than cesium lead chloride composites (CsPbClX2), X = I or Br or Cl.
5. PCE of OIPSC devices which employed HTL have perovskite cubic structure is more than PCE of devices employed HTL have perovskite hexagonal structure. 6. The best PCE of OIPSC is (1.45) to the cubic structure of HTL (CsPbCl3) device .The best PCE of OIPSC is (0.81) to the hexagonal structure of HTL (CsIPbBr2) device . 7. Experimentally , PCE is increased
when the value of the
tolerance factor (t) of pervskite structure of the hole transport materials in OIPSC is closer to unity, i.e. the PCE of OIPSCs devices is improved at the perovskite structure of HTM is closer to the cubic structure.
4.4 Results and Discussions of Free Lead halide Peroveskite Solar Cells: 4.4.1 Stricture properties of peroveskite materials : Figure 4.16(a) depicts the XRD pattern of MAISnCl2 layer (red line) which achieved by deposited perovskite precursor solution using spin coated at speed 2000 rpm on glass substrates followed by annealing at 150 0C. and XRD pattern of MASnI3 layer (black line) as reported in ref [27], for comparison . It can be observed that peaks of XRD of sample MAISnCl2 with lable
agreeing with the data of ref [27].
1600
200
M ASnBr3
M AISnCl2 M ASnI3
120
M ABrSnCl2
1200
160
1200
800
I (CPS)
I (CPS)
120
80
800
80
40
400
400 40
0
0 20
30
40
(degrees)
50
60
0
0 20
30
40
50
(degrees)
(a)
(b)
Fig. 4.16: (a).explains XRD pattern of MAISnCl2 layer on sheet glass substrate (Red curve) comparative with ref [27] (black lines) . (b).XRD patterns of MABrSnCl2 sample (Red curve) comparative with ref [27](black lines) . XRD pattern of MABrSnCl2 layer (red line)was depicted in figure 4.16(b), the sample was prepared by deposited perovskite precursor solution using spin coated at speed 2000 rpm at 30 sec on glass
60
substrates followed by annealing at 150 0C. The MASnBr3
XRD pattern of
layer (black line) as reported in ref [27] inset in figure
4.16(b), for comparison. It can be to observe that peaks of XRD of sample MABrSnCl2 with label
agreeing with the data of ref [27]. The tolerance factor is
calculated
of equation (2-10) to identify the
distorted perovskite
structure, where RI=2.2A, RBr=1.96A ,RCl=1.81A,RSn=1.1A, methylammonium (CH3NH3+) with RA = 1.8A. The evaluations of tolerance factors for the MAISnCl2 and MABrSnCl2 peroveskite structures are calculated, t=0.971968, and, t=0.91365, respectively. The structures is indicated to the cubic stricture due to (0.9 ≤ 𝑡 ≤ 1) [74,75]. Figure 4.17 (a and b) is illustrated top SEM images of MABrSnCl2 film, (c and d) top SEM images of MAISnCl2 film. Scale bars of the left images are 10µm and the right images are 5µm, scanning with high voltage 20kV and magnification (3 and 6) kx, respectively. Samples are prepared by deposited perovskite precursor solution using spin coated at speed 2000 rpm at 30 sec on sheet glass substrate and annealing at 1500C.
Fig. 4.17 depicted SEM images of (a&b) MABrSnCl2 film and (c&d) MAISnCl2 film. SEM images of MABrSnCl2 sample are appeared more crystalline than MAISnCl2 sample which appeared smooth layer, as shown in figure (4.17).
4.4.2 Optical properties of peroveskite materials : The absorption of tin halide perovskite films are explained
in
figure 4.18a and appeared higher absorption to MAISnCl2 film than MABrSnCl2 sample that which are measured in the wavelength range (400-800) nm using a (SPECTRO UV/VIS Double Beam (UVD-3500) Labomed, Inc.) and glass substrates as reference samples .
0.22
0.18
1.6E+11
6E+10
MABrSnCl2 0.17
MAISnCl2 , Eg = 1.72 eV
MAISnCl2 1.2E+11
) 2(eV /cm ) 2
0.21
4E+10
8E+10
( hv*
A bs
0.17
MABrSnCl2 , Eg = 2.13 eV
0.16 0.2
2E+10 4E+10
0.16
0.19
0.15
0
400
500
600
700
800
0 1.2
1.6
2
Wave length (nm)
2.4
E (eV)
(a)
(b)
Fig. 4.18(a) depicts absorption of Visible light of the MAISnCl2 and MABrSnCl2 films. (b) explain energy gap of these films. Plots
inset of (αhv)2 versus photon
energy (hv) for
peroveskite layers on glass substrates are illustrated in Hao et al are reported that the
tin halide Fig 4-18(b).
direct optical band gap energy
values for MASnX3, (X= I, Br or mix of these halide ), are determined (of 1.3 to2.15) eV [27]. Optimum optical properties of tin halide peroveskite materials, available primary materials and easy preparation are reasons to our research,
therefore the peroveskite
materials MAISnCl2 and MABrSnCl2 are employed as harvester light layer of FLPSCs in the present work. Consequently, the values (Eg) of samples are determined by fitting the absorption data to the direct transition equation (2-4). The optical band gap value is obtained by extrapolating the linear part of the curve (αhv)2as a function of photon energy, hv, intercept the (hv) axis at α = 0,
2.8
3.2
as shown in figure 4-18. The values estimated of Eg are inserted in table 4.5. 4.4.3 Parameters of FLPSCs : For the device (FTO/compact-TiO2/ MAISnCl2 scaffold Al2O3/ CuI /Al-electrode)
have low values of (PCE =0.05%) comparative with
the methyl-amine
lead halide peroveskite solar
cells as shown in
figure 4.19 (a) .
Fig 4.19. I-V curve in the forward bias of the of FLPSCs have harvester layer of peroveskite scaffold Al2O3 with (a) MAISnCl2, (b) MABrSnCl2. At the same behavior, the low (PCE = 0.03%) is obtained of the device (FTO/compact-TiO2/ MABrSnCl2 scaffold Al2O3/ CuI /Alelectrode) as shown in figure 4.19(b). Measurements are carried out
under 1 sun illumination (100 mW/cm−2), active area of solar cell is 0.1 cm2, in forward bias and sweeping voltages in the scan-direction with a scan rate of s = 50 mV/s. The all measurements of parameters of FLPSCs in the light test reports were inserted in the table 4.5. It cab to observe that, PCE of FLPSCs devices are depended on the optical properties
of light harvester layer of FLPSCs device , its
increased when increased the absorption and decreased the energy gap of perovskite material of harvester light layer of FLPSCs devices. Table4-5 explains the optical and I–V curve characteristics parameters of FLPSCs. Peroveskite
PCE
materials
%
MAISnCl2
0.05
MABrSnCl2
0.03
Eg (eV)
Voc
Isc
(mV)
(mA)
1.72
400.5
0.03964
2.13
441.3
0.0342
FF
Rs
Rsh
(Ω)
(Ω)
0.31
4200
1490
0.22
28900
8890
4.4.4 Summary of results of FLPSCs :: In summary, the following results were observed that: 1. Solar cells based on tin-based perovskite absorbers, FLPSCs, such as MAISnCl2 or MABrSnCl2 have lower Power Conversion Efficiencies than (PCE) of
OPSCs and OIPSCs devices due to the low
absorption of cubic structure of perovskite absorption layer. 2. Experimentally, PCE of FLPSCs devices are depended on the optical properties of light harvester layer of FLPSCs device, its increased when increased the absorption and decreased the energy band gap of perovskite material of harvester light layer of FLPSCs devices.
General Conclusions
Chapter five Suggestions for Future Work
5.1 General Conclusions : In discussing the results , it is observed the conclusions that : 1. the OPSCs with
construction (FTO/TiO2/(CH3NH3)PbX3
perovskite with Al2O3 scaffold /CuI/Al electrode)
have been
successfully fabricated. 2. In OPSCs devices, an optimum PCE = 2.15% can be achieved by using CH3NH3PbI3 with perovskite tetragonal structure as sensitized absorption layer, harvester light layer of configuration device. An optimum PCE = 0.74% can be achieved by using CH3NH3PbBr3 with perovskite cubic structure as sensitized absorption layer, harvester light layer of configuration device, as shown in table (5.1). 3. Experimentally,
PCE is improved
when increased the
absorption and decreased optical band gap energy of pervskite layer of OPSCs . 4. The percentage of the Br in MAPb(BrxI1−x)3−yCly, proveskite materials, is influencing of optical properties of absorption layer of OPSCs devices at y = 0. When the amount of Cl in term MAPb(BrxI1−x)3−yCly is existed, the changing in the optical energy gap of perovskite materials is very slight increasing or isn't appeared, then energy gap is increased (1.9 to 1.92) at y = 2. 5.
The distorting of perovskite structure is improved of the optical properties of absorption layer caused that the performance of OPSCs devices with tetragonal are better than performance of OPSCs with cubic structure of perovskite materials of absorption layer.
6. In OPSCs, the doing of layer of CuI
is barrier potential
between MAPbI3 layer and Al electrode and it is prevented the recombination of the generated photo-electrons and holes via Al electrode . 7. In OIPSCs, the distorted perovskite
structure
of
HTL is
influencing the PCE of OIPSC devices and values Rs and Rsh of these
devices. Experimentally , the tolerance factor (t) of
perovskite structure of
the hole transport
materials is
influencing of the performance of OIPSCs devices. PCE is increasing when the value of the tolerance factor (t) of perovskite structure of the hole transport materials is closer to unity. 8. Experimentally,
inorganic composites of cesium lead halide
peroveskite HTM with cubic structure have high transparent and larger optical energy gap than HTM have distorted peroveskite structure , Hexagonal structure, which have high absorption and narrow optical energy gap. 9. PCE of OIPSC devices which employed HTM with perovskite cubic structure is more than PCE of devices employed HTM with perovskite hexagonal structure. 10. The best PCE of OIPSC is (1.45) to the cubic structure of HTM (CsPbCl3) device, as shown in table (5.1). The best PCE of OIPSC is (0.81) to the hexagonal structure of HTM (CsIPbBr2) device . 11. Solar cells based on tin-based perovskite absorbers, FLPSCs, such as MAISnCl2 or MABrSnCl2 have lower Power Conversion Efficiencies than (PCE) of OPSCs and OIPSCs devices .The
optimum PCE of FLPSC photovoltaic device is (PCE = 0.05%), as shown in table (5.1). 12. Experimentally, PCE of FLPSCs devices are depended on the optical properties of light harvester layer of FLPSCs device , its increased when
increased the absorption and decreased the
energy band gap of perovskite material of harvester light layer of FLPSCs devices. Table (5.1) shows data of best photo-voltaic devices of the present work PV
Peroviskite
PCE
Voc
Isc
devices
structure
%
(mV)
(mA)
FF
Eg (eV)
(FTO/compact TiO2/MAPbI3 with Al2O3 scaffold/CuI/Al) OPSC
Tetragonal
2.15
595.9
1.397
0.25
1.56
(FTO/compact TiO2/MAPbBr3 with Al2O3 scaffold/CuI/Al) OPSC
Cubic
0.74
614.3
0.29
0.41
2.1
(FTO/compact TiO2/MAPbI3 with Al2O3 scaffold/ CsPbCl3/Al) OIPSC
Cubic
1.45
640.8
1.006
0.22
2
(FTO/compact TiO2/MAPbI3 with Al2O3 scaffold/ CsPbIBr2/Al) OIPSC
Hexagonal
0.81
472.9
0.808
0.21
1.6
(FTO/compact TiO2/MASnICl2 with Al2O3 scaffold/ CuI/Al) FLPSC
Cubic
0.05
400.5
0.039
0.31
1.72
5.2 Suggestions for Future Work : 1. Extensive studies for improving the performance of photovoltaic devices employing the peroveskite materials as harvesting light of solar cells have
environmentally friendly properties and
achieve high efficiency. 2. In fabrication devices , inorganic materials such as C or NiO instead of the perovskite materials employ as HTM of OIPSCs and poly aniline instead of CuI employ as HTM of
OPSCs
and FLPSCs . 3. In Syntheses
perovskite
materials , thermal evaporation
technique instead of the chemical reaction employ to improve the optical properties of peroveskite films and performance of photovoltaic devices .
References : 1. Jiandong Fan, Baohua Jia, and Min Gu," Perovskite-based low-cost and high-efficiency hybrid halide solar cells", Photon. Res, Vol. 2, No. 5, pp (111-120), 2014. 2. James Keith Walton," Thin Film Group II-VI Solar Cells Based on Band- Offsets", A thesis submitted to Portland State University in partial fulfillment of the requirements for the degree of Master of Science, Paper 59, ۳202 . 3. Huawei Zhou, Yantao Shi, Qingshun Dong , Hong Zhang, Yujin Xing, Kai Wang, Yi Du, and Tingli Ma," Hole-Conductor-Free, Metal-Electrode-Free TiO2/CH3NH3PbI3 Heterojunction Solar Cells Based on a Low-Temperature Carbon dx.doi.org/10.1021/jz5017069
|
J.
Phys.
Chem.
Electrode", Lett,
5,
pp(3241−3246), 2014. 4. Tsutomu Miyasaka," Hybrid Photovoltaic Cells Based on Organo Metal Halide Perovskite with Crystalline and Noncrystalline Conductors", International Conference on Hybrid and Organic Photovoltaics ,Lausanne, Switzerland, 11th to 14th May 2014. 5. Nam-Gyu Park," Organometal Perovskite Light Absorbers Toward a 20% Efficiency Low-Cost Solid-State Mesoscopic Solar Cell", 2013 American Chemical Society, dx.doi.org/10.1021/jz400892a, J. Phys. Chem. Lett, 4, pp (2423−2429), 2013. 6. Edri. E, S. Kirmayer, Cahen. D, and Hodes. G, “High opencircuit voltage solar cells based on organic-inorganic lead bromide perovskite”, The Journal of Physical Chemistry Letters, vol. 4, no. 6, pp(897–902), 2013. 7. Etgar, L.; Gao, P.; Xue, Z.; Peng, Q.; Chandiran, A.K.; Liu, B.; Nazeeruddin, M.K.; Grätzel, M. Mesoscopic CH3NH3PbI3/TiO2
heterojunction solar cells. J. Am. Chem. Soc. 134,pp(17396−17399), 2012. 8. Bi. D.Q, Boschloo. G, Schwarzmüller. S, Yang. L, and Johansson. E. M. J, “Efficient and stable CH3NH3PbI3-sensitized
ZnO
nanorod array solid-state solar cells,” Nanoscale 5,pp(11686– 11691), 2013. 9. Hui-Seon Kim, Jin-Wook Lee, Natalia Yantara, Pablo P. Boix, Sneha A. Kulkarni, Subodh Mhaisalkar, Michael Gratzel, and NamGyu Park," High Efficiency Solid-State Sensitized Solar Cell-Based on Submicrometer Rutile TiO2 Nanorod and CH3NH3PbI3 Perovskite Sensitizer", Nano Lett, 13, pp(2412−2417), 2013. 10. Liu. M, Johnston. M. B, and Snaith. H. J, “Efficient planar heterojunction perovskite solar cells by vapour deposition,” Nature 501,pp( 395–398), 2013. 11. Seigo Ito," Printable solar cells", WIREs Energy Environ, 4 ,pp(51– 73), 2015, doi: 10.1002/wene.112 12. Miguel Anaya, Gabriel Lozano, Mauricio E. Calvo, Wei Zhang, Michael B. Johnston, Henry J. Snaith, and Hernán Míguez ," Optical Description of Mesostructured Organic−Inorganic Halide Perovskite Solar Cells", J. Phys. Chem. Lett, 6, pp(48−53), 2015. 13. Kojima. A, Teshima. K, Shirai. Y, and Miyasaka. T, “Organometal halide perovskites as visible-light sensitizers for photovoltaic cells,” J. Am. Chem. Soc. 131,pp (6050–6051) , 2009. 14. Im. J. H , Lee. C. R, Lee. J. W, Park. S. W, and Park. N. G, “6.5% efficient perovskite quantum-dot-sensitized solar cell,” Nanoscale 3, pp(4088–4093), 2011. 15. Lioz Etgar, Peng Gao, Zhaosheng Xue, Qin Peng, Aravind Kumar Chandiran, Bin Liu, Md. K. Nazeeruddin, and Michael Grätzel ,
"Mesoscopic CH3NH3PbI3/TiO2 Heterojunction Solar Cells", J. Am. Chem. Soc, 134, pp(17396--17399) , 2012. 16. Jeong-Hyeok Im, Jaehoon Chung, Seung-Joo Kim and Nam-Gyu Park," Synthesis, structure, and photovoltaic property of a nanocrystalline
2H
perovskite-type
novel
sensitizer
(CH3CH2NH3)PbI3", Nanoscale Research Letters, 7:353,pp(1-7), 2012. 17. In Chung , Byunghong Lee, Jiaqing He1, Robert P. H. Chang and Mercouri G. Kanatzidis," All-solid-state dye-sensitized solar cells with high efficiency", Nature ,Vol, 485, No, 24, pp.486-490, (2012). 18. Zhiliang Ku, Yaoguang Rong, Mi Xu, Tongfa Liu and Hongwei Han, " Full Printable Processed Mesoscopic CH3NH3PbI3/TiO2 Heterojunction Solar Cells with Carbon Counter Electrode", Scientific reports , Nanophotonics and plasmonics -renewable energy , Solar cells - Solar energy and photovoltaic technology, 3 : 3132, (2013), DOI: 10.1038/srep03132. 19. Saman Ghanavi," Organic-inorganic hybrid perovskites as light absorbing/hole conducting material in solar cells ", Master Thesis is submitted to the Uppsala University , ISSN: 1650-8297, 2013. 20. Giles E. Eperon, Samuel D. Stranks, Christopher Menelaou, Michael B. Johnston, Laura M. Herz and Henry J. Snaith," Formamidinium lead trihalide: a broadly tunable perovskite for efficient planar heterojunction solar cells ", The Royal Society of Chemistry , Energy and Environmental
Science. 7 ,288–28۳ , 2014, DOI:
10.1039/c3ee43822h. 21. Aharon. S , Cohen. B. E and Etgar. L ," Hybrid Lead Halide Iodide and Lead Halide Bromide in Efficient Hole Conductor Free Perovskite Solar Cell ", J. Phys. Chem., 118 , 17160, 2014.
22. Kuo-Chin Wang, Jun-Yuan Jeng, Po-Shen Shen, Yu-Cheng Chang, Eric Wei-Guang Diau, Cheng-Hung Tsai, Tzu-Yang Chao, HsuCheng Hsu, Pei-Ying Lin, Peter Chen , Tzung-Fang Guo, and TenChin Wen, " p-type Mesoscopic Nickel Oxide/ Organometallic Perovskite Heterojunction Solar Cells", Scientific reports, 4: 4756, 2014, DOI: 10.1038/srep04756. 23. Christians. J. A, R. Fung. C. M, and Kamat. P.V “An inorganic hole conductor for organo-lead halide perovskite solar cells. Improved hole conductivity with copper iodide,” J. Am. Chem. Soc. 136, 758– 764 (2014). 24. Huawei Zhou, Yantao Shi, Qingshun Dong , Hong Zhang, Yujin Xing, Kai Wang, Yi Du, and Tingli Ma," Hole-Conductor-Free, Metal-Electrode-Free TiO2/CH3NH3PbI3 Heterojunction Solar Cells
Based
on
a
Low-Temperature
Carbon
Electrode",
dx.doi.org/10.1021/jz5017069 | J. Phys. Chem. Lett. 5, 3241−3246, 2014. 25. Jingbi You, Yang (Michael) Yang, Ziruo Hong, Tze-Bin Song, Lei Meng, Yongsheng Liu, Chengyang Jiang, Huanping Zhou, WeiHsuan Chang, Gang Li, and Yang Yang ," Moisture assisted perovskite film growth for high performance solar cells" , Applied Physics Letters 105, 183902(1-5), (2014); DOI: 10.1063/1.4901510. 26. Daniel Bryant , Peter Greenwood , Joel Troughton , Maarten Wijdekop , Mathew Carnie , Matthew Davies , Konrad Wojciechowski , Henry J. Snaith , Trystan Watson , and David Worsley," A Transparent Conductive Adhesive Laminate Electrode for High-Effi ciency Organic-Inorganic Lead Halide Perovskite Solar
Cells", Adv.
Mater.
10.1002/adma.201403939.
26, 7499–7504, 2014,
DOI:
27. Feng Hao, Constantinos C. Stoumpos, Duyen Hanh Cao1, Robert P. H. Chang
and Mercouri G. Kanatzidis," Lead-free solid-state
organic–inorganic halide perovskite solar cells", Nature photonics ,Vol 8 , 489-494, (2014). 28. Belen Suarez
,
Victoria Gonzalez-Pedro,
Rafael S. Sanchez,
Luis Otero , and
Teresa S. Ripolles, Ivan Mora-Sero ,"
Recombination Study of Combined Halides (Cl, Br, I) Perovskite Solar Cells", dx.doi.org/10.1021/jz5006797 | J. Phys. Chem. Lett, 5, 1628−16352014, 2014. 29. Sigalit Aharon, Bat El Cohen, and Lioz Etgar," Hybrid Lead Halide Iodide and Lead Halide Bromide in Efficient Hole Conductor Free Perovskite Solar Cell", American Chemical Society, J. Phys. Chem, 118, 17160, 2014, DOI.org/10.1021/jp5023407, J. Phys. Chem. 30. Chong Chen , Chunxi Li, Fumin Li, Fan Wu, Furui Tan, Yong Zhai and Weifeng Zhang," Efficient perovskite solar cells based on low temperature solution-processed (CH3NH3)PbI3 perovskite /CuInS2 planar heterojunctions", Nanoscale Research Letters 9:457(1-8), 2014. 31. Jie Zhang, Emilio Jos´e Ju´arez-P´erez, Iv´an Mora-Ser, Bruno Vianaa and Thierry Pauport," Fast and low temperature growth of electron transport layers for efficient perovskite solar cells",J. Mater. Chem. A, The Royal Society of Chemistry, 09:14:44, 2015, Downloaded by Universitat Jaume I on 04/02/2015 DOI: 10.1039/c4ta06416j. 32. Hsin-Hua Wang, Qi Chen, Huanping Zhou, Luo Song, Zac St Louis, Nicholas De Marco, Yihao Fang, Pengyu Sun, Tze-Bin Song, Huajun Chena and Yang Yang," Improving the TiO2 electron transport layer in perovskite solar cells using acetylacetonate-based additives ", J. Mater. Chem. A, The Royal Society of Chemistry,
19:17:39, 2015, Downloaded by University of California - Los Angeles on 11/03/2015, DOI: 10.1039/c4ta06394e. 33. Kim. H. S, Lee C. R, Im. J. H, Lee. K. B, and T. Moehl, “Lead iodide perovskite sensitized all-solid-state submicron thin film mesoscopic solar cell with efficiency exceeding 9%,” Sci. Rep. 2, 591 (2012). 34. J. H. Noh. J. H, Im. S. H, Heo. J. H, Mandal. T. N, and Seok. S. I, “Chemical management for colorful, efficient, and stable inorganic– organic hybrid nanostructured solar cells,” Nano Lett. 13, 1764– 1769 (2013). 35. J. Burschka. J, Pellet. N, Moon. S. J, Humphry-Baker. R, and Gao. P, “Sequential deposition as a route to high-performance perovskitesensitized solar cells,” Nature 499, 316–319 (2013). 36. Stranks. S. D, G. Eperon. G. E, Grancini. G, Menelaou. C, and Alcocer. M. J. P, “Electron-hole diffusion lengths exceeding 1 micrometer in an organometal trihalide perovskite absorber,” Science 342, 341–344 (2013). 37. Pablo Docampo , Stefan Guldin , Tomas Leijtens , Nakita K. Noel , Ullrich Steiner , and Henry J. Snaith ," Lessons Learned: From Dye-Sensitized Solar Cells to All-Solid-State Hybrid Devices", Adv. Mater, pp:1-18, 2014, DOI: 10.1002/adma.201400486. 38. Seigo Ito," Printable solar cells",WIREs Energy Environ, 4, pp:51– 73, 2015, DOI: 10.1002/wene.112. 39. Muhammad Imran Ahmed, Amir Habib, and Syed Saad Javaid," Perovskite Solar Cells: Potentials, Challenges, and Opportunities", Hindawi
Publishing
Corporation
,International
Journal
of
Photoenergy, Volume ID 592308,pp:1-13, 2015. 40. Bi. D, Yang. L, Boschloo. G, Hagfeldt. A, and Johansson. E. M. J, “Effect of different hole transport materials on recombination in
CH3NH3PbI3 perovskite-sensitized mesoscopic solar cells,” Journal of Physical Chemistry Letters, vol. 4, no. 9, pp. 1532–1536, 2013. 41. Hui-Seon Kim, Ivan Mora-Sero, Victoria Gonzalez-Pedro, Francisco Fabregat-Santiago,Emilio J. Juarez-Perez, Nam-Gyu Park & Juan Bisquert “Mechanism of carrier accumulation in perovskite thinabsorber solar cells,” Nature Communications, vol. 4, No. 2242, 2013. 42. Dongqin Bi, Lei Yang,
Soo-Jin Moon,
Leif Häggman,
Erik M. J. Johansson,
Michael Grätzel and
Gerrit Boschloo,
Mohammad K. Nazeeruddin,
Anders Hagfeldt., “Using a two-step
deposition technique to prepare perovskite (CH3NH3PbI3) for thin film solar cells based on ZrO2 and TiO2 mesostructures,” RSC Advances, vol. 3, no. 41, pp. 18762–18766, 2013. 43. Sch¨olin. R, Karlsson. M. H, Eriksson. S. K, Siegbahn. H, Johansson. E. M. J, and Rensmo. H, “Energy level shifts in spiroOMeTAD molecular thin films when adding Li-TFSI,” Journal of Physical Chemistry C, vol. 116, no. 50, pp. 26300–26305, 2012. 44. Antonio Abate, Derek J. Hollman, Joël Teuscher, Sandeep Pathak, Roberto Avolio, Gerardino D’Erric, Giuseppe Vitiell, Simona Fantacc, and Henry J. Snaith ,“Protic ionic liquids as p-dopant for organic hole transporting materials and their application in high efficiency hybrid solar cells,” Journal of the American Chemical Society, vol. 135, no. 36, pp. 13538–13548, 2013. 45. Chen. Q, Zhou. H, Hong. Z, Luo. S, Duan. H-S, Wang. H.-H, Liu. Y, Li. G and Yang. Y," Planar Heterojunction Perovskite Solar Cells via Vapor-Assisted Solution Process", J. Am. Chem. Soc, 136, 622– 625, 2013.
46. Im. J.-H , Kim. H.-S, Park. N.-G ," Morphology-photovoltaic property correlation in perovskite solar cells: One-step versus twostep deposition of CH3NH3PbI3" ,APL Mater, 2, 081510, 2014. 47. Pang. S, Hu. H, Zhang. J, Lv. S, Yu. Y, Wei. F, Qin. T, Xu. H, Liu. Z and Cui. G, " NH2CH-NH2PbI3 An Alternative
Organolead
Iodide Perovskite Sensitizer for mesoscopic Solar Cell,"Chem. Mater, 26, 1485–1491, 2014. 48. Hyun Suk Jung and Nam-Gyu Park ," Perovskite Solar Cells: From Materials to Devices", Materials Views solar cells, 11, No. 1,pp:10– 25, 2015. 49. Eperon. G. E, Burlakov. V. M, Docampo. P, Goriely. A, and Snaith. H. J," Morphological Control for High Performance, SolutionProcessed Planar Heterojunction Perovskite Solar Cells", Adv. Funct. Mater. 24, pp:151-157 (2014). 50. Jingbi You, Yang (Michael) Yang, Ziruo Hong, Tze-Bin Song, Lei Meng, Yongsheng Liu, Chengyang Jiang, Huanping Zhou, WeiHsuan Chang, Gang Li, and Yang Yang," Moisture assisted perovskite film growth for high performance solar cells", Applied physics letters 105, 183902(pp1-5), (2014). 51. Im. J.-H , Jang. I.-H , Pellet. N , Grätzel. M , Park. N.-G ," Growth of CH3NH3PbI3 cuboids with controlled size for high-efficiency perovskite solar cells", Nature Nanotechnology 9, pp:927–932 , 2014 , DOI: 10.1038 /NNANO.2014.181 . 52. Edri. E , Kirmayer. S , Henning. A , Mukhopadhyay. S , Gartsman. K , Rosenwaks. Y , Hodes. G , Cahen. D ," Why Lead Methylammonium Tri-Iodide Perovskite-Based Solar Cells Require a Mesoporous Electron Transporting Scaffold (but Not Necessarily a Hole Conductor " Nano Lett, 14 , pp:1000-1004, 2014.
53. Hyun Suk Jung and Nam-Gyu Park ," Perovskite Solar Cells: From Materials to Devices", Materials Views solar cells, 11, No. 1, pp:10– 25, 2015. 54. Stranks. S. D, Eperon. G. E, Grancini. G, Menelaou. C, and Alcocer. M. J. P, “Electron-hole diffusion lengths exceeding 1 micrometer in an organometal trihalide perovskite absorber,” Science, 342, pp:341–344, 2013. 55. Zhao. Y , Nardes. A. M , Zhu. K , "Solid-State Mesostructured Perovskite
CH3NH3PbI3
Solar
Cells:
Charge
Transport,
Recombination, and Diffusion Length", J. Phys. Chem. Lett. 5(3) , pp:490-494, 2014. 56. Ponseca C. S. , Savenije. T. J , Abdellah. M , Zheng. K , Yartsev. A , Pascher. T , Harlang. T , Chabera. P , Pullerits. T , Stepanov. A , Wolf. J.-P , Sundstrom. V ," Organometal Halide Perovskite Solar Cell Materials Rationalized: Ultrafast Charge Generation, High and Microsecond-Long Balanced Mobilities, and Slow Recombination " J. Am. Chem. Soc, 136 , pp:5189 -5192, 2014. 57. Tze Chien Sum and Nripan Mathews ," Advancements in perovskite solar cells: photophysics behind the photovoltaics", Energy Environ. Sci, 7, pp:2518–2534,2014. 58. Park, N.-G., "Organometal perovskite light absorbers toward a 20% efficiency lowcost
solid-state mesoscopic solar cell.", J. Phys.
Chem. Lett. 4,pp: 2423–2429, 2013. 59. Niu. G, Guo. X, and Wang. L, “Review of recent progress in chemical stability of perovskite solar cells,” Journal of Materials Chemistry A, vol. 3, pp:8970–8980, 2014. 60. Pathak. S. K, Abate. A and Leijtens. T “Towards long-term photostability of solid-state dye sensitized solar cells,” Advanced Energy Materials, vol. 4, no. 8, Article ID 1301667, 2014.
61. Leijtens. T, Eperon. G. E, Pathak. S, Abate. A, Lee. M. M, and Snaith. H. J, “Overcoming ultraviolet light instability of sensitized TiO2 with meso-superstructured organometal trihalide perovskite solar cells,” Nature Communications, vol. 4, no. 2885, 2013. 62. Simone Guarnera, Antonio Abate, Wei Zhang, Jamie M. Foster, Giles Richardson, Annamaria Petrozza, and Henry J. Snaith., “Improving the longtermstability of perovskite solar cellswith a porousAl2O3 buffer
layer,” The Journal of Physical Chemistry
Letters, vol. 6, no. 3, pp:432–437, 2015. 63. Poglitsch.
A
methylammonium
and
Weber.
D,
“Dynamic
trihalogenoplumbates
(II)
disorder observed
in by
millimeter-wave spectroscopy,” The Journal of Chemical Physics, vol. 87, no. 11, pp:6373–6378, 1987. 64. Habisreutinger. S. N, Leijtens. T, Eperon. G. E, Stranks. S. D, Nicholas. R. J, and Snaith. H. J, “Carbon nanotube/polymer composites as a highly stable hole collection layer in perovskite solar cells,” Nano Letters, vol. 14, no. 10, pp. 5561–5568, 2014. 65. Michael Grätzel," The light and shade of perovskite solar cells", Nature materials, Vol. 13, pp:838-842, 2014 . 66. Henry J. Snaith, Antonio Abate, James M. Ball, Giles E. Eperon, Tomas Leijtens, Nakita K. Noel, Samuel D. Stranks, Jacob Tse-Wei Wang, Konrad Wojciechowski, and Wei Zhang," Anomalous Hysteresis in Perovskite Solar Cells", J. Phys. Chem. Lett, 5, pp:1511−1515, 2014. 67. Nam Joong Jeon, Jun Hong Noh, Young Chan Kim, Woon Seok Yang, Seungchan Ryu &Sang Il Seok ," Solvent engineering for high-performance inorganic–organic hybrid perovskite solar cells " , Nature Mater. 13, pp:897–903, 2014.
68. Kim. H.-S , Park. N.-G ," Parameters Affecting I–V Hysteresis of CH3NH3PbI3 Perovskite Solar Cells: Effects of Perovskite Crystal Size and Mesoporous TiO2 Layer ", J. Phys. Chem. Lett, 5 , 2927, 2014. 69. Frost. J. M, Butler. K. Brivio. F, Hendon. C. H ,Van Schilfgaarde. M, and Walsh. A, “Atomistic origins of high-performance in hybrid halide perovskite solar cells,” Nano Letters, vol. 14, no. 5, pp. 2584– 2590, 2014. 70. Liu. S, Zheng. F,N. Koocher. N. Z, Takenaka. H, Wang. F, and Rappe. A. M, “Ferroelectric domain wall induced band gap reduction and charge separation in organometal halide perovskites,” The Journal of Physical Chemistry Letters, vol. 6, no. 4, pp. 693– 699, 2015. 71. Lioz Etgar," Semiconductor Nanocrystals as Light Harvesters in Solar
Cells",
Materials,
6,
pp:445-459,
2013,
DOI:10.3390/ma6020445 ISSN 1996-1944. 72. Grégoire Sissoko and Senghane Mbodji," A Method to Determine the Solar Cell Resistances from Single I-V Characteristic Curve Considering the Junction Recombination Velocity (Sf)" Int. J. Pure Appl. Sci. Technol., 6(2) ,pp:103-114,2011. 73. Aqel Mashot Jafar, Kiffah Al-Amara, FarhanLafta Rashid and Ibrahim Kaittan Fayyadh," Fabrication and Characterization of Fluorine-Doped Tin Oxide Transparent Conductive Nano-Films", Elixir Thin Film Tech. 65,pp:19799-19803, 2013. 74. Vasylechko. L, Senyshyn. A, and Bismayer. U, "Perovskite-Type Aluminates and Gallates", In K.A. Gschneidner, Jr., J.-C.G. Bünzli and V.K. Pecharsky, editors: Handbook on the Physics and Chemistry of Rare Earths, Vol. 39, Netherlands: North-Holland,
pp:113-295. 2009, ISBN: 978-0-444-53221-3 © Copyright Elsevier B.V. North-Holland. 75. Martin A. Green1, Anita Ho-Baillie and Henry J. Snaith ," The emergence of perovskite solar cells", Nature Photonics ,Vol 8 , 2014 . 76. Simon A. Bretschneider, Jonas Weickert, James A. Dorman, and Lukas Schmidt-Mende,"Research Update: Physical and electrical characteristics of lead halide perovskites for solar cell applications", APL Materials ; 2 , 040701, pp:1-9, 2014. 77. Tze-Bin Song,ab Qi Chen,
Huanping Zhou,
Chengyang Jiang,
Hsin-Hua Wang, Yang (Michael) Yang, Yongsheng Liu, Jingbi You and Yang Yang," Perovskite solar cells: film formation and properties", J. Mater. Chem. A, 3, 9032-9050 , 2015,
DOI:
10.1039/c4ta05246c. 78. Takeo Oku,"Crystal Structures of CH3NH3PbI3 and Related Perovskite Compounds Used for Solar Cells ",Solar Cells - New Approaches and Reviews,Ch.3,pp:83-101,book edited by Leonid A. Kosyachenko, ISBN 978-953-51-2184-8, Published: October 22, 2015 under CC BY 3.0 license. 79. Baikie, T.; Fang, Y,; Kadro, J. M.; Schreyer, M.; Wei, F.; Mhaisalkar, S. G.; Grätzel, M. and Whitec, T. J, "Synthesis and crystal chemistry of the hybrid perovskite (CH3NH3)PbI3 for solid– state sensitised solar cell applications", Journal of Materials Chemistry A, Vol. 1, pp: 5628–5641, 2013. 80. Priante. D, Dursun. I, M. Alias. M. S, Shi. D, Melnikov. V. A, Ng. T. K, Mohammed. O. M,
Bakr. O. M, and Ooi. B. S," The
recombination mechanisms leading to amplified spontaneous emission
at
the
truegreen
wavelength
in
CH3NH3PbBr3
perovskites", Applied Physics Letters, Vol.106,No. 081902, 2015.
81. Sudam Chavhan, Oscar Miguel, Hans-Jurgen Grande, Victoria Gonzalez-Pedro, Rafael S. S´anchez, Eva M. Barea, Iv´an Mora-Ser´ and Ram´on Tena-Zaer, " Organo-metal halide perovskite-based solar cells with CuSCN as the inorganic hole selective contact", J. Mater. Chem. A, Vol.2,No.12754, 2014. 82. StoumposC. C, Malliakas. C. D, and Kanatzidis. M. G," Semiconducting tin and lead iodide perovskites with organic cations: phase
transitions,
high
mobilities,
and
near-infrared
photoluminescent properties " , Inorg Chem. Inorg. Chem, 52, pp:9019−9038, 2013, DOI: 10.1021/ic401215x. 83. Hao. F , Stoumpos. C. C , Chang. R. P. H , and Kanatzidis. M. G, " Anomalous band gap behavior in mixed Sn and Pb perovskites enables broadening of absorption spectrum in solar cells." , J Am Chem Soc.
Vol. 4, No. 136(22), pp:8094(1-9). 2014, DOI:
10.1021/ja5033259. 84. Mosconi. E, Amat. A, Nazeeruddin. M. K, Gratzel. M and De Angelis. F, " First-Principles Modeling of Mixed Halide Organometal Perovskites for Photovoltaic Applications " ,J. Phys. Chem, 117, pp:13902–13913, 2013. 85. Wang. Y, Gould. T, Dobson. J. F, Zhang. H, Yang. H, Yao. X and Zhao. H,"
Density functional theory analysis of structural and
electronic properties of orthorhombic perovskite CH3NH3PbI3 " ,Phys. Chem. Chem. Phys, 16, pp:1424–1429, 2014. 86. Even. J, Pedesseau. L , Jancu. J. M and Katan. C, " Importance of Spin-Orbit Coupling in Hybrid Organic/Inorganic Perovskites for Photovoltaic Applications ", J. Phys. Chem. Lett, 4, pp:2999–3005, 2013.
87. Andrea Del Quarto," Meso-Superstructured Solar Cell based on Organo-Metal Halide Perovskite", Master thesis submitted to Anno Accademico ,2015. 88. Sulabha K. Kulkarni, "Nanotechnology : Principles and Practice", Hand book ,Department of Physics , University of Pune, Pune, New Delhi, pp: 60-63,1st Print 2009. 89. Miguel Anaya , Gabriel Lozano, Mauricio E. Calvo , Wei Zhang , Michael B. Johnston,
Henry J. Snaith, and Hernan Míguez ,"
Optical Description of Mesostructured Organic−Inorganic Halide Perovskite Solar Cells", J. Phys. Chem. Lett, 6, pp:48−53, 2015, DOI.org/10.1021/jz502351s. 90. Lee, M. M., Teuscher, J., Miyasaka, T., Murakami, T. N. & Snaith, H. J." Efficient hybrid solar cells based on meso-superstructured organometal halide perovskites ", Science 338, pp:643–647, 2012. 91. Ball, J. M., Lee, M. M., Hey, A. & Snaith, H. J., "Low-temperature processed meso-superstructured to thin-film perovskite solar cells" ,. Energy Environ. Sci. 6, pp:1739–1743, 2013. 92. Manda Xiao, Fuzhi Huang, Wenchao Huang, Yasmina Dkhissi, Ye Zhu,Joanne Etheridge, Angus Gray-Weale,
Udo Bach, Yi-Bing
Cheng, Leone Spiccia. , "A fast deposition-crystallization procedure for highly efficient lead iodide perovskite thin-film solar cells. Angew" ,. Chem. Int. Ed. 53, pp:9898–9903, 2014. 93. Huanping Zhou, Qi Chen, Gang Li, Song Luo, Tze-bing Song, HsinSheng Duan, Ziruo Hong, Jingbi You, Yongsheng Liu1, Yang Yang, ." Interface engineering of highly efficient perovskite solar cells" ,. Science 345, pp:542–546 ,2014. 94. Pablo Docampo, James M. Ball, Mariam Darwich, Giles E. Eperon and Henry J. Snaith," Efficient organometal trihalide perovskite planar-heterojunction solar cells on flexible polymer substrates",
Nature
communications,
Vol.
4,
No.
۳670,
2013,
DOI:
10.1038/ncomms3761 . 95. Hotra. Z, Stakhira. P , Cherpak. V , Volynyuk. D , Voznyak. L , Gorbulyk. V , Tsizh. B," Effect of thickness of a CuI hole injection layer on the properties of organic light emitting diodes" , doi: 10.4302/plp.2012.1.13 Photonics letters of Poland , Vol. 4, No.1,pp: 35-37, 2012. 96. Jae-Hyun Lee, Dong-Seok Leem, Hyong-Jun Kim, and Jang-Joo Kim," Effectiveness of p-dopants in an organic hole transporting material", Applied physics letters, Vol. 94, No. 123306, pp1-3 , 2009. 97. Yuan Ye, Xu Run, Xu Hai-Tao, Hong Feng, Xu Fei, and Wang LinJun," Nature of the band gap of halide perovskites 𝐴𝐵𝑋3 (𝐴 = CH3NH3,Cs; 𝐵 = Sn, Pb; 𝑋 = Cl, Br, I): First-principles calculations", Chin. Phys. B Vol. 24, No. 11, pp:116302,1-5, 2015. 98. Lei Yang ," Hole Transport Materials for Solid-State Mesoscopic Solar Cells", Dissertation presented at Uppsala University to be publicly examined in Uppsala, Friday, 31 October 2014 at 13:15 for the degree of Doctor of Philosophy. 99. Quinten A. Akkerman, Valerio D’Innocenzo, Sara Accornero, Alice Scarpellini, Annamaria Petrozza, Mirko Prato, and Liberato Manna,” Tuning the Optical Properties of Cesium Lead Halide Perovskite Nanocrystals by Anion Exchange Reactions", J. Am. Chem. Soc, 2015, DOI: 10.1021/jacs.5b05602 . 100. Quinten A. Akkerman, Silvia Genaro Motti, Ajay Ram Srimath Kandada, Edoardo Mosconi, Valerio D’Innocenzo, Giovanni Bertoni, Sergio Marras, Brett A. Kamino, Laura Miranda, Filippo De Angelis,
Annamaria Petrozza,
Mirko Prato, and Liberato
Mannam, "Solution Synthesis Approach to Colloidal Cesium Lead
Halide Perovskite Nanoplatelets with Monolayer-Level Thickness Control" , J. Am. Chem, January 2016, DOI: 10.1021/jacs.5b12124. 101. Somma. F, Nikl. M, Nitsch. K, Giampaolo. C Phani. A. R and Santucci. S, "The growth, structure and optical properties of CsIPbI2 co-evaporated thin films" , Superficies y Vacío, 9, pp:62-64, 1999. 102. Christopher Eames, Jarvist M. Frost, Piers R.F. Barnes, Brian C. O’Regan, Aron Walsh1 and M. Saiful Islam, "Ionic transport in hybrid lead iodide perovskite solar cells",Nature communications ,Vol. 6, No. 7497, pp 1-8, 2015. 103. Mizusaki, J., Arai, K. & Fueki, K. "Ionic conduction of the perovskite-type halides", Solid State Ionics 11, pp:203–211, 1983. 104. Narayan, R. L. and Suryanarayana, S. V, "Transport properties of the perovskitetype halides", Mater. Lett, 11, pp:305–308 , 1991. 105. Kuku, T. A, " Ionic transport and galvanic cell discharge characteristics of CuPbI3", Thin Solid Films, 325, pp:246–250, 1998.
Appendix A
(a)
(b)
a) I-V of OPSCs (FTO/Compact TiO2/scaffold Al2O3 with CH3NH3PbBr3/CuI/Al electrode ) device. b) I-V of OPSCs (FTO/Compact TiO2/scaffold Al2O3 with CH3NH3IPbCl2/CuI/Al electrode ) device.
(a)
(b)
a) I-V of OPSCs (FTO/Compact TiO2/scaffold Al2O3 with CH3NH3BrPbI2/CuI/Al electrode ) device. b) I-V of OIPSCs (FTO/Compact TiO2/scaffold Al2O3 with CH3NH3I3/CsClPbBr2/Al electrode ) device.
(a)
(b)
a) I-V of OIPSCs (FTO/Compact TiO2/scaffold Al2O3 with CH3NH3I3/CsIPbBrCl/Al electrode ) device. b) I-V of OIPSCs (FTO/Compact TiO2/scaffold Al2O3 with CH3NH3I3/CsIPbCl2/Al electrode ) device.
Appendix B
Publications :
1.
2.
3.
الخالصة : يهدف البحث الحالي إلى توليد طاقة نظيفة من خاليا البروفسكايت الشمسية ذات الكلفة الواطئة . تم تحضير خاليا البروفسكايت الشمسية من هاليدات الرصاص العضوية ) (OPSCمع طبقة ) (CuIالتي تستخدم حامالت الشحنة األكثرية ,الفجوات . (HTM) ,تم دراسة الخصائص البصرية والتركيبية لطبقة االمتصاص المتحسسة ,لمركبات البروفسكايت ) , (CH3NH3PbX3إذ أن (X=I, Br or Cl) ,أو مزيج من هذه الهالوجينات لهذا الصنف من الخاليا الشمسية .تشير دراسة ) (XRDأن المركب ) (CH3NH3PbX3ذات تركيب رباعي أو مكعب عندما ) (X=I, Brوتركيب رباعي عندما يكون مزيج من )(X=I, Cl وتركيب مكعب عندما يكون مزيج من ) . (X= Br ,Clتم انجاز أفضل كفاءة تحويل للطاقة
) (PCE = 2.15%عندما تمتلك خلية البروفسكايت
الشمسية
المركب
) (CH3NH3PbI3كطبقة امتصاص متحسسة .تم اختبار الخاليا تحت ظروف محاكاة ضوء الشمس ). (100 mW cm−2 تم تحضير خاليا البروفسكايت الشمسية ) (OIPSCمن مركب مثيل امين ايوديد الرصاص العضوي مع طبقة بروفسكايت ال عضوية )) (CsPbIxBryCl3-(x+yالتي تستخدم كحامالت الشحنة األكثرية ,الفجوات (HTM) ,في المختبر .وتشير دراسة ) (XRDأن المركب )) (CsPbIxBryCl3-(x+yذات تركيب مكعب عندما ) (x = 0, y = 0, 2وتركيب سداسي عندما الشمسية
) . (x = 1, y = 0,1,2تم انجاز أفضل كفاءة تحويل للطاقة للخاليا
) (PCE =1.45%أو ) (PCE = 0.81%عندما تمتلك طبقة ) (HTMتركيبا
مكعب أو سداسي (CsPbCl3) ,أو ) ,(CsIPbBr2على التوالي .تم اختبار الخاليا تحت ظروف محاكاة ضوء الشمس ). (100 mW cm−2 تم تحضير خاليا البروفسكايت الشمسية الخالية من الرصاص ) (FLPSCالتي تستخدم كلوريد القصدير االمائي ) (anhydrous SnCl2بدل هاليدات الرصاص ) (PbX2لتحضير مركبات طبقة االمتصاص البروفسكايت المتحسسة للضوء .خاليا ) (FLPSCتعطي كفاءة قليلة مقارنة بخاليا ) (OPSCوخاليا ) . (OIPSCأفضل كفاءة تحويل للطاقة للخاليا الشمسية ) (FLPSCهي ) . (PCE = 0.05%تم اختبار الخاليا تحت ظروف محاكاة ضوء الشمس ). (100 mW cm−2
تم دراسة طبوغرافية السطح لألغشية الرقيقة لجميع النماذج باستخدام مجهر القوة الذرية ) (AFMأو المجهر الماسح االلكتروني ) . (SEMتم التحقق من اتجاهات البلورية لمركبات البروفسكايت باستخدام تحليل ) . (XRDتم دراسة الخصائص البصرية لألغشية البروفسكايت الرقيقة لكل الخاليا الشمسية باستخدام جهاز التحليل الطيفي في مجال األشعة المرئية وفوق البنفسجية ,تم دراسة مخططات ) (I-Vلجميع الخاليا الشمسية باستخدام منظومة القياس المتكاملة للخلية الشمسية تتضمن منظومة قياس مخطط ) (I-Vومنظومة محاكاة الشمس.
جمهورية العراق وزارة التعليم العالي والبحث العلمي جامعة بغداد كلية العلوم
تصنيع وخصائص الخاليا الشمسية البروفسكايت أطروحة مقدمة إلى مجلس كلية العلوم -جامعة بغداد وهي جزء من متطلبات نيل درجة دكتوراه فلسفة في الفيزياء من قبل
عقيل مشحوت جعفر (بكلوريوس علوم في الفيزياء )0222 (ماجستير علوم في الفيزياء )0222
بأشراف أ د .مهدي حسن سهيل 2017م
٤١۳۸ھ
