Comparative performance analysis of lead-free perovskite solar cells based on FASnI₃, CsSnI₃, KGeCl₃, and CsGeI₃...

Perovskite solar cells (PSCs) are promising for next-generation photovoltaics, but their commercial viability is hindered by the toxicity of lead (Pb). This study investigates the performance of lead-free PSCs by comparatively evaluating four different perovskite absorber layers: FASnI₃, CsSnI_3, KGeCl₃ and CsGeI₃. Using SCAPS-1D numerical simulations, the impact of the absorber material, along with the thickness and carrier concentration of the electron and hole transport layers (ETL and HTL), on photovoltaic parameters was systematically analyzed. Results show that among the four materials, FASnI₃ delivers the highest overall power conversion efficiency (PCE), followed by CsSnI₃ and KGeCl₃, while CsGeI₃ exhibits the lowest. Subsequently, detailed optimization of FASnI₃-based PSCs reveals the crucial and complex interplay between ETL (TiO₂) and HTL (Spiro-OMeTAD) parameters (thickness, carrier concentration, and defect density) on device performance. A key finding is that the defect density in the ETL has a more significant adverse impact on PCE compared to the HTL, primarily by enhancing non-radiative recombination. This study provides vital insights and optimization strategies for developing high-efficiency, environmentally friendly lead-free perovskite solar cells.