Towards high-efficiency flexible lead-free RbGeI3 perovskite solar cells: numerical insights from SCAPS-1D

Abstract

Lead-free perovskite materials have attracted increasing attention as viable substitutes for conventional lead-based absorbers in next-generation photovoltaic technologies. In this study, the performance of a flexible perovskite solar cell (FPSC) employing rubidium germanium iodide (RbGeI3) as the absorber material was simulated numerically using the SCAPS 1-D program. The device architecture utilizes C60 as the electron transport layer (ETL) and poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) as the hole transport layer (HTL). To enhance device performance, key structural and electrical parameters were systematically optimized. The optimized device parameters include the thickness of the absorber material, carrier concentration, and defect density. The influence of these optimized parameters on the photovoltaic characteristics namely the open-circuit voltage (VOC), short-circuit current density (JSC), fill factor (FF), and power conversion efficiency (PCE) was carefully analysed. The results showed that the optimized device structure can achieve a maximum efficiency of 31.75%. The VOC was 1.19 V, JSC was 31.27 mA cm−2, while FF was 85.08%. The enhanced photovoltaic performance is mainly associated with more efficient charge carrier extraction and the suppression of recombination losses within the optimized device structure. These findings suggest that RbGeI3 is a promising lead-free perovskite absorber for the development of high-performance flexible solar cells, offering potential for environmentally friendly next-generation photovoltaic applications.