Performance enhancement of hybrid organic–inorganic CH3NH3SnI3 and CH3NH3PbI3 perovskite solar cells: A comprehensive optimization study

: The environmental concerns associated with lead-based perovskite solar cells have driven considerable interest toward lead-free alternatives, yet few studies have fairly compared the two under the same optimized conditions. This study presents a systematic and comprehensive numerical simulation, using the one-dimensional Solar Cell Capacitance Simulator, of two planar n-i-p heterojunction perovskite solar cells, lead-free CH 3 NH 3 SnI 3 and lead-based CH 3 NH 3 PbI 3 , sharing the same device architecture: Glass/Fluorine-doped tin oxide/Electron transport layer/Perovskite/Hole transport layer/Back contact. Both devices were subjected to identical optimization protocols covering electron and hole transport materials, layer thicknesses, doping concentrations, absorber defect densities, and back contact metals. For the tin-based device, tin oxide and nickel oxide were identified as the optimal electron and hole transport materials, respectively, while zinc oxide and molybdenum trioxide were found optimal for the lead-based counterpart, with both transport layers converging on an optimal thickness of 20 nm in the two structures. The optimized tin-based device employed an absorber thickness of 700 nm, a donor density of 5×10 18 cm -3 in the electron transport layer, an acceptor density of 5×10 15 cm -3 in the hole transport layer, and an absorber defect density of 1×10 13 cm -3 , while the lead-based device was optimized at an absorber thickness of 650 nm under the same doping and defect conditions. Platinum was selected as the back contact for both structures based on its superior work function alignment. The fully optimized tin-based device achieved a power conversion efficiency of 28.85%, with an open-circuit voltage of 0.98 V, a short-circuit current density of 33.78 mA/cm 2 , and a fill factor of 86.63%, significantly outperforming the optimized lead-based device, which reached 21.10% under the same conditions. Defect density analysis confirmed that both devices maintain stable performance up to 1×10 13 cm -3 , beyond which recombination losses drive substantial efficiency degradation. These results demonstrate that tin-based perovskite solar cells, when properly optimized, not only match but clearly outperform their lead-based counterparts, establishing a clear direction for high-performance lead-free photovoltaic development.