Simulation study of CZTS/CZTSe tandem solar cell by using SCAPS-1D software

Abstract

The solar spectrum can be divided by tandem solar cells into several subcells that have different bandgaps which convert, more effectively, the light into electricity than the single cells. In this study, the simulation of the photovoltaic (PV) characteristics of a CZTS/CZTSe tandem solar cell, based on structures of copper zinc tin sulfide (CZTS) as a top cell and copper zinc tin selenide (CZTSe) as a bottom cell, was accomplished by using SCAPS-1D simulator under AM1.5 illumination. Initially, the simulation of single CZTS and CZTSe solar cells was performed to give efficiency of 14.37 % and 17.87 %, respectively, which are in good agreement with the literature results. Before feeding with filtered spectrum, the simulated PV parameters of the CZTS/CZTSe tandem solar cell are the conversion efficiency (η) of 20.68 % and the shortcircuit current density (Jsc) of 20.205 mA/cm2 of the top and bottom cells with arbitrary normal thicknesses. Furthermore, and in order to reach the matching current, both top and bottom cells have been investigated at different thicknesses for tandem configuration after validation, where the performance of the top and bottom cells is at thicknesses ranged from 0.05-0.5 μm and 0.1-1 μm, respectively. The performance of the tandem solar cell is determined after filtered spectrum feeding and current matching. The Jsc of CZTS/CZTSe tandem solar cell is 20.33 mA/cm2 for 0.255 μm thick of the top, CZTS, cell and 0.8 μm of the bottom, CZTSe, cell. The maximum η of 22.98 % is reached for tandem structure design with open circuit voltage (Voc) enhancing of 1.48 V