Theoretical and device-level insights into FASnBr3 perovskite solar cells: a synergistic approach Combining density functional theory and SCAPS-1D

• Perovskite FASnBr 3. • Density functional theory (DFT) • SCAPS-1D numerical simulations. • J sc of 15.88 mA cm −2 , a V oc of 1.530 V, and an FF of 88.50% • TCO/WS 2 /FASnBr 3 /Cu 2 O/Au device exhibited the highest PCE of 19.80% In the present study, the lead-free organic–inorganic hybrid perovskite FASnBr 3 , where FA represents formamidinium, is investigated as a promising solar absorber material with high photovoltaic performance and environmental sustainability. In response to the environmental and health concerns associated with lead-based perovskites, increasing attention has been directed toward the development of lead-free alternatives that can maintain excellent optoelectronic properties. This work focuses on the previously synthesized FASnBr 3 compound, with a detailed investigation of its structural and optoelectronic properties using density functional theory (DFT), alongside a comprehensive evaluation of FASnBr 3 -based solar cell performance through SCAPS-1D numerical simulations. The DFT analysis reveals that FASnBr 3 possesses a direct bandgap of 1.775 eV and a high absorption coefficient, indicating its strong potential for photovoltaic applications. At the device level, multiple solar cell architectures were examined using SCAPS-1D by incorporating both inorganic and organic electron and hole transport layers. Specifically, WS 2 , C 60 , and PCBM were employed as electron transport layers (ETLs), while NiO, Cu 2 O, PEDOT:PSS, and Spiro-MeOTAD were considered as hole transport layers (HTLs), with Au used as the back contact for all simulated devices. In total, twelve different device configurations were analyzed to identify the optimal structure for maximum power conversion efficiency (PCE). Key photovoltaic parameters, including open-circuit voltage (V oc ), short-circuit current density (J sc ), and fill factor (FF), were systematically evaluated by varying the combinations of ETLs, HTLs, and absorber layer thickness. The simulations indicate that an optimized absorber thickness of 600 nm, along with a defect density of 10 15 cm −3 and a donor density of 10 18 cm −3 , leads to enhanced device performance. Among all the investigated configurations, the TCO/WS 2 /FASnBr 3 /Cu 2 O/Au device exhibited the highest PCE of 19.80% compared to other ETL-HTL combinations. The corresponding photovoltaic parameters were also optimized, yielding a J sc of 15.88 mA cm −2 , a V oc of 1.530 V, and an FF of 88.50%. Furthermore, the operating temperature was varied to examine the thermal behavior and operational stability of FASnBr 3 -based devices. Overall, the favorable physical, optical, and photonic properties of the lead-free FASnBr 3 perovskite, which has already been experimentally synthesized, together with the promising simulated photovoltaic performance, demonstrate that this material is a strong candidate for future solar cell development.