Optimization & enhancement of KGeCl₃-based perovskite solar cells through charge transport layer engineering

The growing demand for efficient, stable, and environmentally friendly photovoltaic technologies has motivated the exploration of nontoxic perovskite materials such as KGeCl₃. However, the performance of KGeCl₃-based perovskite solar cells (PSCs) depends heavily on the compatibility of charge transport layers (CTLs) and optimization of device parameters. In this study, six PSC configurations were simulated using SCAPS-1D software, incorporating CTLs such as Alq₃, CSTO, V₂O₅, nPB, and Sb₂S₃. Key optimization steps included analyzing CTL-perovskite heterojunction compatibility, evaluating band offsets, electric potential distribution, and recombination rates, followed by fine-tuning layer thickness, doping concentration, defect density, electrode work function, and back-end reflectivity. These optimizations significantly reduced recombination losses, enhanced charge carrier extraction, and improved light absorption, leading to substantial performance improvements. The CSTO-KGeCl₃-nPB configuration demonstrated the highest power conversion efficiency (PCE) of 29.30%, outperforming other optimized configurations, such as Alq₃-KGeCl₃-nPB and Alq₃-KGeCl₃-Sb₂S₃, which achieved PCE values of 25.19% and 24.87%, respectively. This comprehensive optimization study highlights the potential of KGeCl₃ as a promising absorber material for PSCs. The findings pave the way for developing efficient, stable, and sustainable photovoltaic solutions, contributing to the advancement of clean energy technologies.