Photo-catalytic or Photo-electrochemical

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Perovskite solar cells (PSCs) exceeding a power conversion efficiency (PCE) of 20% .... the ⟨110⟩-oriented family, A′2AmBmX3m+2, which includes 1-D chain (m = 1) and 2-D .... functional calculations (with quasi-particle corrections).

Photo-catalytic or Photo-electrochemical Decomposition of Water

National Centre for Catalysis Research Indian Institute of Technology Madras Presentation No. 4 Dated 5th April 2017

Questions, suggestions and remarks these can form a habit to all of us

Photo-catalytic or Photo-electrochemical Decomposition of Water 1.One of the promising steps towards generating clean and renewable alternatives for fossil fuels. Band structure and redox potentials match are pursued. The dynamic nature of the electronic energy levels is postulated. 2.The need for knowing the positions of the energy levels of conduction band and valence band of semiconductors and methodology for determining them are outlined. 3.The layer type of semiconductors and water adsorption was postulated

State of the Art Challenges 1. 2. 3. 4.

Slow reaction rate, low yields Arresting catalyst deactivation Low quantum efficiency Need for catalysts active in VIS range with >10% QE – For economic viability-Yet to be realized

Phil. Trans. R. Soc. A., 2010, 368, 3343-3364.

(a)

(b)

(a) PCE record plot of perovskite solar cells. (b) Crystal structure of perovskite adopting the form of ABX3, where A is methyl ammonium, B is Pb(II) or Sn(II), and X is Cl, Br, or I, or a coexistence of several halogen elements. Journal of Nanomaterials, vol. 2015, Article ID 241853, 10 pages, 2015. doi:10.1155/2015/241853

Carbon nanotube act as an electron accepter thereby reducing the electron- hole recombination J. Phys. Chem. C, 2011, 115 (44), pp 22025–22034

J. Am. Chem. Soc., 2009, 131 (17), pp 6050–6051

A schematic illustration of perovskites-sentitized TiO2 undergoing photoexcitation and electron transfer (left). The Incident Photon to Electron Conversion Efficiency (IPCE) spectra for perovskites sensitized solar cell

Next Generation Perovskite Solar Cells with New WorldRecord Performance Perovskite solar cells (PSCs) exceeding a power conversion efficiency (PCE) of 20% have mainly been demonstrated by using mesoporous titanium dioxide (mp-TiO2) as an electron-transporting layer. However, TiO2 can reduce the stability of PSCs under illumination (including ultraviolet light). Lanthanum (La)–doped BaSnO3 (LBSO) perovskite would be an ideal replacement given its electron mobility and electronic structure, but LBSO cannot be synthesized as well-dispersible fine particles or crystallized below 500°C. A superoxide colloidal solution route for preparing an LBSO electrode under very mild conditions (below 300°C) is developed. The PSCs fabricated with LBSO and methylammonium lead iodide (MAPbI3) show a steady-state power conversion efficiency of 21.2%, versus 19.7% for a mp-TiO2 device. The LBSO-based PSCs could retain 93% of its initial performance after 1000 hours of full Sun illumination. First release: 30 March 2017 www.sciencemag.org (Page numbers not final at time of first release) 1, Downloaded from http://science.science 6620 Cite as: S. S. Shin et al., Science 10.1126/science.aam6620 (2017)

Hybrid lead perovskites containing a mixture of organic and inorganic cations and anions have led to solar cell devices with performance and stability that are better than those of their single-halide analogs. 207Pb solidstate nuclear magnetic resonance and single-particle photoluminescence spectroscopies show that the structure and composition of mixed-halide and likely other hybrid lead perovskites are much more complex than previously thought and are highly dependent on their synthesis. While a majority of reports in the area focus on the construction of photovoltaic devices, this Perspective focuses instead on achieving a better understanding of the fundamental chemistry and photo-physics of these materials, because this will aid not only in constructing improved devices but also in generating new uses for these unique materials. ACS Energy Lett. 2017, 2, 906-914

Organic Inorganic Perovskites • New generation of photoactive materials • Absorber in solar cells and significant progress towards improved efficiency, fabrication and scale up process. • Organic inorganic perovskite materials in photovoltaics as well as photo-electrochemical applications

Background Solar Cell History: 1839: Alexandre Edmond Becquerel son of physicist Antoine Cesar Becquerel and father of physicist Henri Becquerel 1873: Willoughby Smith, an English engineer , discovered the photoconductivity of selenium 1883: American inventor Charles Fritts made the first solar cells from selenium 1940 Russell Shoemaker Ohl, a semiconductor researcher at Bell Labs. Patented with 1% Efficiency 1953 Daryl Chapin, Calvin Fuller and Gerald Pearson

April 25, 1954: Bell Labs Demonstrates the First Practical Silicon Solar Cell

Past History of Organic-Inorganic Perovskites H.L. Wells (1893) synthesized Alkali-metal lead and tin halides

Christian Møller (1958) first crystallographic studies that determined that caesium lead halides had a perovskite structure with the chemical formula CsPbX3(X = Cl, Br or I) Dieter Weber (1978) replaced caesium with methylammonium cations (CH3NH3+)to generate the first three-dimensional organic– inorganic hybrid perovskites Mitzi, D. B. Methylammonium lead iodide, CH3NH3PbI3, has both interesting optical and electronic properties that have been actively investigated during the past two decades

Recent Development in PSC

Tolerance Factor (t) and Octahedral Factor (μ) t = (RA+ RX )/(√2(RB+ RX)

μ = RB/RX

Cubic Perovskite Structure Symmetric Tetragonal or Orthorhombic Structures

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