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 10⁴ 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 C₆₀ 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 CsPbBr₃ but harder than for CsPbI₃.

Graphic Abstract

: Band alignments of perovskites including CsPbI₃, CsPbBr₃, CsPbI₂Br and CsSnI₂Br together with the commonly used electron transport materials and hole transport materials are presented using the first principles calculations, which could help to improve the all inorganic CsPbI₂Br solar cell performance.