Precision Design of Lead-Free Sr ₃ SbCl ₃ Perovskite Solar Cells: Role of Electron Transport Layers and Interface Optimization

This work presents a systematic SCAPS-1D simulation of lead-free perovskite solar cells (PSCs) employing Sr₃SbCl₃ as a light-absorbing material. A comparative analysis of six electron transport layers (ETLs), CdS, SnS₂, ZnSe, In₂S₃, WS₂, and Zn-(O,S) was performed based on conduction band alignment, carrier mobility, and interfacial compatibility. Among them, ZnSe, In₂S₃, and WS₂ exhibited the most superior photovoltaic performance and were selected for detailed optimization. Key parameters, including ETL and absorber thickness, doping concentration, and bulk and interface defect densities, were systematically optimized to suppress recombination and enhance charge transport. The electric field distribution and Shockley-Read-Hall recombination were analyzed to elucidate the carrier lifetimes and recombination dynamics. The Au/Sr₃SbCl₃/WS₂/FTO configuration achieved the highest power conversion efficiency (PCE) of 31.4%, outperforming ZnSe- and In₂S₃-based devices with PCEs of 30.92% and 30.93%, respectively. Notably, while all three configurations displayed identical open-circuit voltages (V_oc = 0.958 V), WS₂ provided superior short-circuit current densities (J_sc) and fill factors, attributed to optimal interfacial energetics and elevated electron mobility. This investigation highlights the significance of ETL selection and interface engineering in the advancement of stable, nontoxic perovskite devices that achieve efficiencies above 30%. This work establishes Sr₃SbCl₃ as a novel, environmentally benign, and sustainable alternative for next-generation perovskite photovoltaics.