ZnxCd1−xS as prospective window layer in CdTe thin film solar cells from numerical analysis

In this work, a conventional structure of CdS/CdTe cells was investigated, where Zn_xCd_1-xS window material that possesses wider bandgap replaced CdS window layer. The effect of composition variation in Zn_xCd_1-xS was analysed for high efficiency cell using AMPS 1D Simulator and the optimal value of x was found to be around 8%. Moreover, to explore the possibility of high efficiency, ultra thin and stable Zn_xCd_1-xS/CdTe cells the CdTe absorber layer thickness was decreased to the extreme limit and 1μm CdTe layer showed reasonable range of efficiency with stability. The thickness of Zn_xCd_1-xS window layer was reduced to 80 nm to increase the overall cell performance with the insertion of ZnO/Zn₂SnO₄ as the buffer layer. The proposed cell with Zn_xCd_1-xS as window layer showed promising result with an efficiency of 22.42% (Voc = 0.98 V, Jsc = 29.35 mA/cm², FF = 0.85) using As₂Te₃ as back surface field (BSF) and copper (Cu) as final back contact. The cell normalized efficiency was found to be decreased linearly at the gradient -0.24/C with the operating temperature that indicated better stability of Zn_xCd_1-xS/CdTe solar cells.