Synthesis of Perovskite (FAPbI ) Solar Cell Using

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Vanessa L. Pool , Benjia Dou, Douglas G. Van Campen , Md I. Ahmad, Maikel F. A. M.van Hest. “Thermal engineering of FAPbI3 perovskite material via radiative ...
Synthesis of Perovskite (FAPbI3) Solar Cell Using Rapid Thermal Processing Instrument Sooraj Kumar, Md. Imteyaz Ahmad* Department of Ceramic Engineering Indian Institute of Technology (BHU)Varanasi *[email protected] ABSTRACT Hybrid halide perovskites have emerged as a promising optoelectronic material with high photovoltaic power conversion efficiency (PCE) i.e. above 23 % by a solution based processing. In order to reduce the thermal budget of processing and ease in scalability we have designed and developed a Rapid Thermal Processing (RTP) instrument which has ramp rate 28 ̊C/sec and can be utilized for rapid and uniform annealing compact TiO2 and FAPbI3 layer. Here the compact TiO2 (electron transport layer) and FAPbI3 perovskite (absorber layer) were prepared by solution processing method followed by annealing in RTP. The results were compared for conventional hotplate and tube furnace annealing with RTP annealing.

Temperature (C)

INTRODUCTION for roll to roll processing, high throughput processing. Perovskite is most promising materials for RTP has potential to overcome challenges future photovoltaic technologies having of scalability and stability. •Unique electronic structure •Can work in vacuum and inert atmosphere. •Ramp rate nearly 30 ̊C/s. •Band gap tunability-(1.47eV to 2.3eV) •Superior charge transport •Roll to roll processing(fast cell fabrication) •Low raw material cost •Low thermal budget of processing. Major problems in commercialization Ramp rate=27.35 ͦC/ s 700 •Stability 600 y = 27.354x + 37.761 500 •Scalability 400 Linear (Temp©) 0 Band gap Profile

NREL efficiency data

RTP Chamber

EXPERIMENTAL

1.Preparation of c-TiO2 (ETL)layer by spin coating and annealing in RTP and Furnace TTIP 1.5ml

Acetic acid 0.5 ml

c- TiO2

Transparent TiO2

10 Time (s) 20 Ramp rate profile

30

1 ml DMF

Spin coating 5 times on cleaned substrate Annealed on 500 ̊C for 2hours in furnace Characterization and perovskite layer coating

Spin coating 5 times on cleaned substrate Annealed on 500 ̊C for 5 minutes in RTP. Characterization and perovskite layer coating

Hotplate The solution was spin coated on c-TiO2/FTO substrate (In glove box). The substrate was then annealed on hotplate at 170̊C for 10 minutes Characterizations and coating of SpiroOMeTAD.

RTP The solution was spin coated on c-TiO2 coated FTO substrate Annealed in RTP for 45 seconds at 170̊C

32mg of Spiro in 0.5ml CB

Spiro OMeTAD Solution in Glovebox

Solution was coated on top of perovskite layer

50µm

•Peak positions are confirming anatase phase. •Band gap is in the required range.

100nm

•RTP annealed c-TiO2 was pinhole free. •Will prevent short circuit b/w FTO and FAPbI3. •Will enhance efficiency. •Has comparable transparency. •Films are annealed by absorption of radiation hence uniform heating.

Hotplate Annealed d-phase along with a-phase Hotplate annealing RTP annealing observed after •Transformation back •a-phase(black) stable annealing to d-phase(Yellow) in for more than 30 days 2h

10 µm

RTP Annealed Complete transformation to a-phase observed after annealing

3 µm

10 µm

3 µm

Perovskite (FAPbI3 ) Solution in Glove box

8.8µl of LiTFSI sol

SpiroOMeTAD

Furnace Annealed

Characterizations and coating of Spiro- OMeTAD.

3.Preparation of Spiro-OMeTAD (HTL) using LITSFI and TBP 14.4µl of TBP solution

Furnace Annealed

100nm

1 ml DMF

Vigorous stirring at room temperature for 3h RTP

50µm

0.7 M FAI

This mixture was stirred for 2 hours in glove box.

Furnace

RTP Annealed

0.1203gm FAI 0.7M PbI2

Transparent TiO2 solution

RTP Annealed

2.Preparation of perovskite layer by spin coating and annealing in RTP and on hotplate 0.3227g m PbI2

Ethanol 10ml

RESULTS & DISCUSSION Results

Temp©

300 200 100 0

Common cell architecture

4.Preparation of counter electrode by thermal evaporation •Counter electrode (gold) of thickness 30 nm was sputtered on the Spiro-OMeTAD using the mask

CONCLUSION I In this study it has been demonstrated that using RTP following can be achieved, . a- phase of FAPbI3 was found more stable when annealed in RTP. RTP can be utilized for roll to roll processing of perovskite cell. Very compact and pinhole free surface morphology of c- TiO2. Pinhole free surface morphology of FAPbI3 Thermal budget of processing reduced by 40 times. Processing was done within few hours compared to a day. Annealing profile for c-TiO2

400 nm

400 nm

•RTP annealed perovskite was compact. •Might lead efficient carrier transfer.

•Hotplate annealed perovskite had pinhole. •Might lead to recombination losses.

REFERENCE 1. Vanessa L. Pool , Benjia Dou, Douglas G. Van Campen , Md I. Ahmad, Maikel F. A. M.van Hest “Thermal engineering of FAPbI3 perovskite material via radiative thermal annealing and in situ XRD” Nature communication doi:10.1038/ncomms14075 2. Md. Imteyaz Ahmad, Douglas G. Van Campen, Jeremy D. Fields, Jiafan Yu, Vanessa L. Pool “ Rapid thermal processing chamber for in-situ x-ray diffraction” Review of Scientific Instruments 86, 013902 (2015). 3. 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” Energy Environ, Sci., 2014, 7, 982–988.

ACKNOWLEDGEMENTS

Authors would like to thank Mr. Asim Aftab, and Mr. Harsh Baldi of Dept. of Ceramic Engineering for their help in experiments, and to Mr. Harshvardhan Singh and Mr.Hrish Kumar for their help while developing RTP. Authors would also like to thank DIH(IIT BHU) offering opportunity to develop RTP and CIF(IIT BHU) for characterizations.