Conference Papers
Permanent URI for this collectionhttps://idr.nitk.ac.in/handle/123456789/28506
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Item Improvement in performance of CZTSSe solar cell by using cadmium free buffer layers(SPIE, 2021) Prabhu, S.; Pandey, S.K.; Chakrabarti, S.Cadmium Sulphide(CdS) has been the most preferred n-type buffer layer and Indium Tin Oxide(ITO) is the popular window layer in kesterite solar cells. Cadmium being toxic and Indium being a rare earth element, continuous efforts are being made to replace these materials from kesterite solar cells structure. In this work, ZnS, ZnSe, and Zn0.8Sn0.2O are considered as possible alternatives for CdS. Similarly, Aluminium doped Zinc Oxide(AZO) is considered as an alternative for ITO. Firstly, a cell model with CdS and ITO (Mo/CZTSSe/CdS/ZnO/ITO) is developed using SCAPS-1D software. To optimise the performance parameters namely open-circuit voltage(Voc), short-circuit current density(Jsc), fill factor(FF), and the power conversion efficiency (PCE) for irradiation under normal working conditions, thickness and the composition ratio of the absorber layer(CZTSSe) are evaluated through numerical simulations. PCE of 14.51% is achieved for a 40% of Sulphur content and 2 um thickness of Cu2ZnSn(SxSe1-x)4 when CdS is used as the buffer layer. For the same structure, replacing ITO with AZO results in a PCE of 14.62%. Use of Cadmium-free buffer layers ZnS, ZnSe, and Zn0.82Sn0.18O with ITO as window layer result in PCE of 13.98%, 14.28%, and 14.53%, respectively. For the Cadmium-free buffer layers, an improvement in PCE is achieved when ITO is replaced by AZO, with the highest being 14.62% for Zn0.82Sn0.18O. This can be attributed to the smaller conduction band offset, which reduces the recombination of photogenerated carriers and improves the carrier transport in the solar cell. The above results indicate that the Zn0.8Sn0.2O and AZO can be potential candidates for the buffer layer and window layer, respectively, for high-performance and cheap kesterite solar cells. © 2021 SPIE.Item Simulation and optimization of nanostructure incorporated CZTS solar cell towards higher performance(SPIE, 2022) Prabhu, S.; Pandey, S.K.; Chakrabarti, S.Kesterite solar cells require a novel high-research implementation to replace the costlier Copper Indium Gallium Selenide (CIGS) solar cells. This study, attempts to demonstrate the performance improvement of kesterite solar cells using multiple quantum wells (MQWs). A numerical simulation approach using Atlas software from Silvaco is used. Firstly, a baseline model of the best performing Cu2ZnSnS4(CZTS) solar cell Mo/CZTS/CdS/i-ZnO/ITO with 11% power conversion efficiency (PCE) is implemented. Further, to exploit the use of MQWs, Cu2ZnSn(SxSe1-x)4 (CZTSSe) with 40% sulfur content is added as well material in a series of wells while keeping the CZTS as the barrier material. This structural modification facilitates the absorption of lower energy photons by the lower bandgap well material. Further, MQW induced quantized energy levels and higher electric fields help to increase the carrier collection, thereby increasing the solar cell's short circuit current density (Jsc) and overall power conversion efficiency (PCE). A detailed study on the effect of well and barrier thickness on the solar cell performance is done, and a well thickness of 5 nm and a barrier thickness of 10 nm was chosen for further optimization. The number of wells is also optimized to 70, which results in the highest performance of the solar cell. This structural modification and optimization remarkably improved Jsc by 48.76% (rel.) and PCE by 34.72% (rel.) compared to solar cells without nanostructures. Moreover, with an optimized structure, an external quantum efficiency (EQE) of over 95% is achieved with the optimized structure. © © 2022 SPIE.