This study focuses on optimizing the performance and long-term stability of lead-free methylammonium tin bromide (MASnBr₃) perovskite solar cells (PSCs) using advanced interface layers and graphene. The research aims to enhance the efficiency and sustainability of PSCs, which have gained significant attention due to their rapid performance improvements and high potential for renewable energy applications. The study employs numerical simulations with the SCAPS-1D software to model and optimize the device structure, including the thicknesses and defect densities of the absorber and interface layers. Key findings include: 1. **Interface Layer Optimization**: Graphene is used as an interface layer between the hole transport layer (HTL) and the absorber layer, while ZnO/Al and 3C−SiC are used as interface layers between the electron transport layer (ETL) and the perovskite layer. These layers significantly improve charge carrier extraction and reduce recombination losses. 2. **Absorber Layer Thickness**: Adjusting the thickness of the perovskite layer from 100 to 700 nm optimizes performance, with the highest efficiency achieved at 700 nm. 3. **Defect Density**: Reducing the defect density in the perovskite layer enhances efficiency, with the optimal doping concentration at 10¹⁸ cm⁻³. 4. **Graphene and 3C−SiC Thickness**: The thickness of the graphene and 3C−SiC layers also affects performance, with the optimal thicknesses being 0.3 μm for graphene and 0.015 μm for 3C−SiC. The optimized device structure, ZnO/3C−SiC/MASnBr₂/graphene/CuO/Au, achieves theoretical power conversion efficiencies of 31.97%, fill factors of 89.38%, a current density of 32.54 mA/cm², a voltage of 1.112 V, and a quantum efficiency of 94%. This research highlights the potential of MASnBr₃ as a non-toxic perovskite material for sustainable energy applications.This study focuses on optimizing the performance and long-term stability of lead-free methylammonium tin bromide (MASnBr₃) perovskite solar cells (PSCs) using advanced interface layers and graphene. The research aims to enhance the efficiency and sustainability of PSCs, which have gained significant attention due to their rapid performance improvements and high potential for renewable energy applications. The study employs numerical simulations with the SCAPS-1D software to model and optimize the device structure, including the thicknesses and defect densities of the absorber and interface layers. Key findings include: 1. **Interface Layer Optimization**: Graphene is used as an interface layer between the hole transport layer (HTL) and the absorber layer, while ZnO/Al and 3C−SiC are used as interface layers between the electron transport layer (ETL) and the perovskite layer. These layers significantly improve charge carrier extraction and reduce recombination losses. 2. **Absorber Layer Thickness**: Adjusting the thickness of the perovskite layer from 100 to 700 nm optimizes performance, with the highest efficiency achieved at 700 nm. 3. **Defect Density**: Reducing the defect density in the perovskite layer enhances efficiency, with the optimal doping concentration at 10¹⁸ cm⁻³. 4. **Graphene and 3C−SiC Thickness**: The thickness of the graphene and 3C−SiC layers also affects performance, with the optimal thicknesses being 0.3 μm for graphene and 0.015 μm for 3C−SiC. The optimized device structure, ZnO/3C−SiC/MASnBr₂/graphene/CuO/Au, achieves theoretical power conversion efficiencies of 31.97%, fill factors of 89.38%, a current density of 32.54 mA/cm², a voltage of 1.112 V, and a quantum efficiency of 94%. This research highlights the potential of MASnBr₃ as a non-toxic perovskite material for sustainable energy applications.