Numerical simulation of all-inorganic CsPbI3 / CsGeI3 bilayer perovskite solar cells

Perovskite solar cells (PSCs) have gained momentum in the photovoltaic field because of its high-power conversion efficiency (PCE) and low-cost manufacturing process. In the screening of perovskite materials, CsPbI₃ has attracted widespread due to its good thermal stability, high degradation resistance and excellent photovoltaic performance. However, CsPbI₃'s high band gap (1.73 eV) limits its development in single-junction PSC. In this study, we constructed a double absorption layer CsPbI₃/CsGeI₃ PSC with SCAPS-1D (solar cell capacitance simulator). Compared with the conventional single-layer structure of CsPbI3 PSC, the double-layer CsPbI₃/CsGeI₃ PSC has a broader absorption spectrum and better photovoltaic performance. We systematically analyzed the thickness and defect density of the absorber layer, and the operating temperature on the cell performance and obtained the optimal parameters. In addition, we selected the best electron transport layer and hole transport layer (ETL/HTL) for the double absorption layer CsPbI₃/CsGeI₃ PSC. Under the optimized conditions, all cell performance parameters improve significantly, and its PCE is as high as 28.92%.