Advanced optimization of lead-free FASnI3 photovoltaics with spiro-OMeTAD/ZnO structure for high power conversion efficiency

In the global quest for a more sustainable and clean energy source, solar photovoltaics continue to be a key technology for fossil fuel substitution. To meet the demand for future generations of sustainable energy, solar energy devices must combine high efficiency, environmental safety, stability, and cost-effectiveness. Organic–inorganic lead-based perovskite solar cells (PSCs) offer such a solution. But their lead content introduces serious environmental and health concerns. To address this problem, introducing non-toxic tin (Sn) in place of lead provides a promising path toward safer and more sustainable perovskite-based solar cells. This study presents an extensive theoretical investigation of organic-inorganic lead-free FASnI 3 PSCs with the structure Spiro-OMeTAD/FASnI 3 /ZnO/FTO, simulated by SCAPS-1D. The effects of absorber thickness, defect density, band gap, and operating temperature were systematically optimized. The initial configuration achieved a power conversion efficiency (PCE) of 25.25% (V oc = 1.19 V, J sc = 27.49 mA/cm², FF = 76.58%). Under optimized parameters, the device reached a PCE of 33.40% without an interface defect and 25.17% with interface defect. These simulation results demonstrate the potential of FASnI 3 for high-performance, lead-free perovskite photovoltaic solar cells and provide a greener pathway toward environmentally safe, commercially viable solar cell technologies.