All-inorganic perovskite CsPbI2Br as a promising photovoltaic absorber: a first-principles study

Hybrid organic-inorganic halide perovskites as promising solar cell materials have great concern on their stability. Recently, all-inorganic perovskite CsPbI2Br has been considered as a first-class alternative with good stability as well as a suitable bandgap, and the highest solar cell efficiency has been achieved up to 16%. Using the first-principles calculations, we found that (i) CsPbI2Br is stable in tetragonal cell with a direct bandgap of 1.67 eV under PBE functional calculations approximating to the experimental value (1.92 eV). The upper valence band is derived from the antibonding states of s-p coupling, and the CBM is mainly composed of Pb-p states. (ii) The optical absorption is as strong as 10(4) cm(-1)in the visible light range which can compare to that of the popular halide organic-inorganic hybrid perovskite. (iii) The electron transport material (ETM) in popular perovskite solar cells such as TiO2, ZnO, SnO2, PCBM and C(60)together with the hole transport material (HTM) such as P3HT, CuI, NiO, PTAA and Spiro are suitable for CsPbI2Br solar cell devices. The band offset between different perovskites demonstrates that it is easier for CsPbI2Br to be doped p-type than for CsPbBr(3)but harder than for CsPbI3.