Non-Toxic Indium Selenide Quantum Dots as Photosensitizers and Cu2ZnSnS2Se2 Counter Electrode for Solar Cells

Saha, Sukanya and M, Deepa (2017) Non-Toxic Indium Selenide Quantum Dots as Photosensitizers and Cu2ZnSnS2Se2 Counter Electrode for Solar Cells. Masters thesis, Indian Institute of Technology Hyderabad.

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Abstract

6 Abstract Quantum Dots Sensitized Solar Cells (QDSCs), are one of the most promising third generation solar cell s , where quantum dots are used as light harvester s due to their unique characteristics such as adjustable band gap, plausibility of multiple exciton generation, high absorption coefficient and low cost. Over the past few years, the power conversion efficiency (PCE) of QDSCs has shown a meteoric enhancement from less than 1% to above 12 %. The photovoltaic performance of QDSCs is how ever limited by charge recombination at the electrode/electrolyte interface. QDSCs of lead and cad mium chalcogens are widely used; these well - known quantum dots are toxic pollutant s for the environment and human being s . So the goal of this work was to find a non - toxic or less toxic, stable photosensitizer. Indium selenide ( In 2 Se 3 ) satisfied these qualities , it has a band gap of 1.87 eV with a  max value of 660 nm. In 2 Se 3 is a n - type semiconductor. An approach involving the use of visible light absorbing material In 2 Se 3 quantum dots (QDs) as photosensitizer s, coupled with highly electrocatalytic Cu 2 ZnSnSe 2 S 2 (CZTSeS) as counter electrode (CE) and with a poly (2 - hydroxy ethylmethacrylate) (PHEMA) gel as the solar cell electrolyte , resulted in a remarkable power conversion efficiency (PCE) , which is presented in this work . T he application of TiO 2 /In 2 Se 3 to a QDSC has been done for the first time. The s tructural characterizations based on SEM analysis, X - Ray Diffraction, optical characterizations such as flu orescence and absorption spectral analyses, lifetime decay as well as cyclic voltammetry, impedance studies and J - V characteristics have been executed . From J - V characteristics of TiO 2 /In 2 Se 3 /C - fabric - CZTSeS cell , the power conversion efficiency ( PCE ) of the champion cell is 4.15% whereas the PCE of TiO 2 /In 2 Se 3 /C - fabric - CZTSeS is 2.97% , which shows that CZTSeS enhances the cell efficiency up to 39.7%. These studies show the potential of In 2 Se 3 as photoabsorbers, CZTSSe as an effective CE and a PHEMA ge l as a good hole transport material for practical applications of QDSCs

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