Front interface defect signature and benefits of CdSeTe thickness and band gap in CdSeTe/CdTe graded solar cell

Abstract

Thin film solar cells based on CdTe absorber suffer from abnormal current density – voltage (J-V) shapes and open‑circuit voltage deficit due to suboptimum device architecture, non-optimal back contact and bulk absorber limiting factors, such as low doping density, grain boundary and low carrier lifetime. In this study, we investigate the role of window/absorber interface defects properties in the J‑V curve shape and the combined effect of CdSexTe1-x thickness and band gap on the device performance using SCAPS-1D. For donor-type interface defects no abnormalities are reported in the J-V curve shape of the device. Acceptor-like defects show strong effect on the J-V shape and two types of anomalies in the J-V curve are reported, hysteresis and s-kink. Those abnormalities are eliminated when the defects concentration at the front interface is bellow or equal to. The simulations also point out the optimum CdSeTe thickness and band gap to achieve simultaneously high values of open-circuit voltage and short-circuit density, as well as, high conversion efficiency and fill factor. We demonstrate that further device structural optimization is required in MZO/CdSeTe/CdTe solar cell.