Study on the Key Parameters Affecting the Power Conversion Efficiency of Cs₂AgBiBr₆-Based Perovskite Solar Cells

The lead-free halide double perovskite material A 2 BB’X 6 represented by Cs 2 AgBiBr 6 , has higher potential as a photovoltaic material since it has good electronic and optical properties in recent years. However, the highest power conversion efficiency (PCE) achieved for solar cells made with Cs 2 AgBiBr 6 as the light-absorbing layer in experiments is only 2.51%. To investigate this phenomenon, we used the Solar Cell Capacitance Simulator (SCAPS) simulation software to build five solar cell models with the structure of FTO/ZnO/Light-absorbing layer/Cu 2 O/Au based on different light-absorption layer materials. Two reasons causing the low PCE of Cs 2 AgBiBr 6 solar cells were identified. On the one hand, interlayer defects in Cs 2 AgBiBr 6 film synthesis significantly decreased the fill factor (FF), thereby reducing the quantum efficiency (QE). On the other hand, Cs 2 AgBiBr 6 ’s larger indirect bandgap resulted in a narrower absorption range. Additionally, it was demonstrated that adjusting the material thickness and alloying method could, respectively, improve the two aforementioned issues. When the thickness of the light-absorbing layer material was 300[Formula: see text]nm, the FF increased from 39.88% to 55.01%, resulting in an optimal PCE of 3.88% for the solar cell. Alloying increased the short-circuit current ([Formula: see text]) from 8.44[Formula: see text]mA/cm 2 to 21.24[Formula: see text]mA/cm 2 , leading to a simulated PCE increase of 8.92% for solar cells based on Cs 2 NaSb[Formula: see text]In[Formula: see text]I 6 . This work, from the perspective of device simulation, is highly significant for improving the photoelectric conversion efficiency of Cs 2 AgBiBr 6 -based perovskite solar cells in experimental settings. It offers new insights for optimizing solar cell efficiency.