Optimization of vertical gradient Pb-Sn hybrid perovskite solar cells using SCAPS (Solar Cell Capacitance Simulator)

Abstract

Lead-tin hybrid perovskite solar cells emerge as a promising alternative to traditional lead-based cells, addressing environmental and stability concerns, however their efficiency lags. During the fabrication of lead-tin mixed perovskites, the Pb/Sn ratio varies across the film due to different solubilities under various processing conditions. To tackle this issue, we propose a novel perovskite absorber with a vertical gradient in the lead-tin ratio. Our study employs SCAPS-1D simulations to investigate the performance of ITO/HTL/gradient perovskite/ETL/Ag cell structures with different transport layer materials. We systematically analyze the impact of doping levels, defect density states, and interfacial defects in the absorber layer on device efficiency. Through optimization of the device structural parameters, reflecting real experimental conditions, we achieved an energy conversion efficiency of 24.84%. This efficiency is comparable to that of lead-based perovskite solar cells. Interestingly, simulations suggest that omitting the electron transport layer still yields an efficiency above 23.5%, potentially simplifying the fabrication process. This finding indicates that vertically graded Pb-Sn hybrid perovskite solar cells hold great promise for high-efficiency solar cell applications.