Electronic Structure and Optical Properties of ABI 3 Inorganic Lead‐Free Halide Perovskites: A DFT + U Study

Organic–inorganic lead halide perovskites have attracted extensive attention from researchers due to their excellent optoelectronic properties. However, the toxicity of lead limits their further development and practical applications. Here, the DFT + U method was employed to investigate the electronic structure and optical properties of ABX 3 halide perovskites, aiming to screen potential absorption materials for solar cells. Through formation energy calculations, 23 stable structures were selected from 30 ABX 3 halide perovskites. Among these 23 stable structures, 9 Sn/Ge perovskites (CsSnI 3 , LiSnI 3 , NaSnI 3 , KSnI 3 , RbSnI 3 , CsGeI 3 , NaGeI 3 , KGeI 3 , and RbGeI 3 ) are p‐type direct semiconductors with high thermal stability, low effective mass, high absorption coefficient, and suitable bandgaps (1–1.5 eV). Notably, the absorption coefficients of Ge‐based perovskites are higher than those of Sn‐based perovskites. Specifically, the average absorption coefficient of CsGeI 3 is 2.23 times that of CsSnI 3 , exhibiting excellent visible light utilization ability. Our calculation results can provide valuable guidance for the design of high‐efficiency inorganic lead‐free perovskite solar cells.