Theoretical investigations on enhancement of photovoltaic efficiency of nanostructured CZTS/ZnS/ZnO based solar cell dev
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Theoretical investigations on enhancement of photovoltaic efficiency of nanostructured CZTS/ZnS/ZnO based solar cell device S. Vallisree1 · R. Thangavel1 · T. R. Lenka2 Received: 20 October 2017 / Accepted: 1 February 2018 © Springer Science+Business Media, LLC, part of Springer Nature 2018
Abstract We report a model of CZTS/ZnS/ZnO nanorod device designed using optical coefficients of each thin film layers obtained from the experimental results. The J − V characteristic was compared with available experimental result in order to validate our model. In this model, we have examined the effect of thickness of each material layer, CZTS minority carrier lifetime, CZTS acceptor concentration, shallow and deep states formed during the fabrication process on the photovoltaic device parameters. The thickness of the CZTS absorber, buffer and window layer are optimized using optoelectronic simulations and the optimum thicknesses are found to be 2.5–3.0 µm, 30 nm and 500 nm respectively. Also, we analyzed the effect of shallow states and deep states in CZTS and ZnO layer on the photovoltaic parameters of the solar cell. After optimization of the above mentioned parameters, it is observed that the efficiency of the solar cell is improved from 3.69 to 7.65%.
1 Introduction Thin film solar cells are used worldwide for power generation due to its low cost deposition with each layer thickness in the order of few micrometers. Photovoltaic solar cells are developed using various semiconducting materials such as amorphous silicon, polycrystalline CdTe, CIGS etc [1, 2]. Even though CIGS solar cells have reported world record efficiency upto 21.7% [3], its production is limited by the use of rare earth metals such as In and Ga. CZTS solar cells are promising candidates for emerging photovoltaic technologies owing to its abundance in nature and Zn and Sn are available at low cost. In addition to these, kesterite materials possess low band gap tunable in the range 1–1.7 eV and has high absorption coefficient greater than 1 04 cm−1 [4–7] thereby allowing efficient absorption of photons with absorber thickness of few micrometers. Several kesterite based solar cells fabricated by researchers using different deposition methods are reported in [8, 9]. However, the performance of kesterite based solar cells is limited by open circuit voltage deficit * R. Thangavel [email protected] 1
Department of Applied Physics, Indian Institute of Technology (ISM), Dhanbad, Jharkhand 826004, India
Department of Electronics and Communication Engineering, National Institute of Technology Silchar, Silchar, Assam 788010, India
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and meager efficiency. Optical modeling of thin film solar cells help us to elucidate the device physics and chemistry of materials in order to minimize losses and improve the efficiency. Efficiency improvement of CIGS and CZTS solar cells are studied through numerical simulations by optimization of various material parameters in [10, 11] respectively. The improvement of CZTS solar cell performance with the bifacial
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