Lead-Free p-n Homojunction Cs-Doped and Pure FASnI₃-based perovskite solar cells–a performance analysis using SCAPS 1D simulator

• This study compares a Cs-doped p-n homojunction PSC with (FTO/TiO 2 /n-FA 75 Cs 25 SnI 3 /p-FA 75 Cs 25 SnI 3 /CuSCN/Au) based structure and a pure (FTO/TiO 2 /n-FASnI 3 /p-FASnI 3 /CuSCN/Au) based structure. • The impact of variation in defect density, thickness and temperature are thoroughly analyzed using SCAPS-1D simulation software. • The simulation results with optimized parameters, the Cs-doped structure has increased PCE, reduced recombination losses and enhanced charge carrier transport compared to the pure structure. • An open circuit voltage (V OC ) of 1.039 V, short circuit current density (J SC ) of 35.66 (mA/cm 2 ), fill factor (FF) of 86.46% and PCE of 32.03% are achieved in the Cs-doped structure. The development of lead-free perovskite solar cells (PSCs) has received significant interest in recent years, particularly in tin-based perovskites such as formamidinium tin iodide (FASnI₃). However, FASnI 3 performance is limited by its poor stability, high defect density, low power conversion efficiency (PCE) and oxidation susceptibility. In this study, a Cs-doped p-n homojunction PSC with (FTO/TiO 2 /n-FA 75 Cs 25 SnI 3 /p-FA 75 Cs 25 SnI 3 /CuSCN/Au) based structure is modeled and compared with a pure (FTO/TiO 2 /n-FASnI 3 /p-FASnI 3 /CuSCN/Au) based structure. A comparison study of Cs-doped FASnI₃ and pure FASnI₃ is conducted and the impact of Cs doping in the p-n homojunction structure is analyzed using one-dimensional solar cell capacitance simulator (SCAPS-1D) software. The impact of variation in defect density, thickness and temperature are thoroughly analyzed using SCAPS-1D simulation software. Based on the simulation results with optimized parameters, the Cs-doped (FTO/TiO 2 /n-FA 75 Cs 25 SnI 3 /p-FA 75 Cs 25 SnI 3 /CuSCN/Au) structure increases the PCE, decreases recombination losses and enhances charge carrier transport compared to the pure (FTO/TiO 2 /n-FASnI 3 /p-FASnI 3 /CuSCN/Au) structure. Under optimized conditions, an open circuit voltage (V OC ) of 1.039 V, short circuit current density (J SC ) of 35.66 (mA/cm 2 ), fill factor (FF) of 86.46% and PCE of 32.03% are achieved in the Cs-doped structure. These results highlight the potential of Cs-doped (FTO/TiO 2 /n-FA 75 Cs 25 SnI 3 /p-FA 75 Cs 25 SnI 3 /CuSCN/Au) p-n homojunction PSCs structure, which is much better than the pure (FTO/TiO 2 /n-FASnI₃/p-FASnI₃/CuSCN/Au) based p-n homojunction PSC structure. This work validates that the p-n homojunction structure is effective for achieving highly efficient PSCs which produces lower carrier recombination losses, going beyond the current planar heterojunction PSCs.