Achieve near-infrared absorption in Cs3Sb2Br9 through 3d orbital energy level splitting to construct high-performance intermediate band solar cells

Through high-throughput screening, this study identified Cs3Sb2Br9 (triclinic system) layered perovskite, with an optimal bandgap as the primary material for constructing intermediate bands. Due to the complex electronic configuration of transition metals, the partially filled 3d orbitals are utilized to construct intermediate bands. 25 % of transition metal ions were introduced into the Cs3Sb2Br9 lattice, resulting in octahedral contraction. The induced Jahn-Teller (J-T) effect caused the 3d orbitals to split into four energy levels, which coupled with the intrinsic energy bands, form four types of band structures. The intermediate bands within the original energy bandgaps are formed by doping with Cr, Mn, Fe, and Ni. The study suggests that intermediate bands constructed from eg orbitals have better dispersion levels than those constructed from t2g orbitals, making them more suitable for intermediate band construction. Further computational results demonstrated that Ni doping, with d7 electron configurations, successfully introduced a well-dispersed intermediate band. This leads to strong absorption of near-infrared light, expanding the absorption range of Cs3Sb2Br9 to approximately 1550 nm. Therefore, in device simulations of solar cells, Ni-doped Cs3Sb2Br9 generated a significant number of photogenerated carriers, achieving an optimal efficiency of 43.51 %. This study introduces a novel approach to improve the optical sensitivity of lead-free layered perovskites in near-infrared photodetectors and intermediate band optoelectronic devices.