Modeling of a Tandem Solar Cell Structure Based on CZTS and CZTSe Absorber Materials

Abstract

In this paper, we simulated a double junction cell based on top CdS/Cu2ZnSnS4 cell, stacked on a bottom CdS/Cu2ZnSnSe4 cell. We started by studying the perfomance of the bottom solar cell, based on the copper zinc tin selenide Cu2ZnSnSe4 (CZTSe) absorber. Then, we evaluated the photovoltaic parameters of the tandem cell at the optimized thickness of the copper zinc tin sulfide Cu2ZnSnS4 (CZTS) absorber of the top cell, where the top and bottom cells deliver the same photocurrent density. We achieved A maximum efficiency of 24.68% with an open circuit voltage of 1.33 V and a photocurrent density of 16.54 mA/cm² for the thicknesses 413.8 nm and 2 µm of CZTS and CZTSe absorbers, respectively. İn order to improve power conversion efficiency, light trapping effects was studied. The use of randomly textured top cell absorber allows the reduction of its thickness to 270 nm. An efficiency of 24.71% was then obtained. Finally, the effect of replacing the toxic CdS buffer absorber with the ZnS material was investigated.