Computational insights into wide bandgap lead free perovskite solar cells for silicon based tandem configurations

The quest for high-efficiency solar cells has led to significant research into lead-free perovskite materials, particularly tin-based perovskites. This study investigates the photovoltaic properties of various compositions of FASn(I_{1 - x}Br_x)₃ perovskites for potential application in solar cells. Computational simulations explore the influence of absorber layer thickness and bulk defect density on the performance of lead-free single-junction perovskite solar cells. Additionally, a two-terminal monolithic tandem solar cell configuration comprising FASn(I_0.75Br_0.25)₃ for the top cell and silicon for the bottom cell is proposed and analyzed. The proposed tandem device, with a 1.66 eV perovskite top cell and a 1.12 eV c-Si-based heterojunction, achieved a maximum power conversion efficiency (PCE) of 33.39%, an open circuit voltage (V_OC) of 2.04 V, a short-circuit current density (J_SC) of 21.14 mA/cm², and a fill factor (FF) of 77.26%. For comparison, the perovskite top cell alone achieved a V_OC of 1.36 V, J_SC of 20.44 mA/cm², FF of 75.51%, and PCE of 21.07%. The bottom cell under AM 1.5G illumination exhibited a V_OC of 0.68 V, J_SC of 40.36 mA/cm², FF of 80.18%, and PCE of 22.05%. Under a filtered spectrum, the bottom cell produced a V_OC of 0.67 V, J_SC of 30.46 mA/cm², FF of 79.13%, and PCE of 16.33%. This performance comparison highlights the enhanced efficiency, voltage, and overall stability provided by the tandem structure over individual cells. This examination encompassed the variation of absorber layer thickness, J-V curves under illumination, quantum efficiency, energy band diagrams, filtered spectra, and tandem photovoltaic parameters governing the conversion efficiency. The study demonstrates the potential of lead-free perovskite/silicon tandem devices, showcasing their promise for the future development of high-efficiency and stable solar cells.