Comparative performance analysis of lead-free perovskite solar cells based on FASnI3, CsSnI3, KGeCl3, and CsGeI3 absorbers with optimized charge transport layers
Abstract
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, CsSnI3, 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.