Improved Performance of Lead‐Free Perovskite Solar Cells Based on Multi‐Absorber MASnI3/CsGeI3 Heterojunction by Device Simulation

Abstract Lead‐free perovskite solar cell (PSC) is the direction of future development of PSCs due to its reduced toxicity. However, the power conversion efficiency (PCE) of the lead‐free PSCs is still lagging behind their lead‐based counterparts, which hinders their further application. Multi‐absorber approach can effectively overcome this problem as it allows the maximum utilization of solar spectrum. Therefore, in this study a novel lead‐free MASnI 3 /CsGeI 3 heterojunction structure is proposed to boost the performance of PSCs based on single CsGeI 3 absorption layer. The critical device parameters including absorber thickness, defect density, doping concentration, and back contact work function are studied and optimized using the numerical software SCAPS‐1D. Under optimized conditions, PSCs based on Sn/Ge bilayer structure yield a considerable PCE of 16.15%, significantly higher than the single CsGeI 3 based PSCs (optimized PCE of 7.43%) with higher thermal stability. The simulation results indicate a huge potential of the proposed multi‐absorber heterojunction structure for highly efficient lead‐free PSCs, which will contribute to achieving clean and sustainable energy in the future.