Exploring the air stability of all-inorganic halide perovskites in the presence of photogenerated electrons by DFT and AIMD studies

Abstract

Developing ambient air and light stable metal halide perovskites could lead to tremendous progress in reducing energy waste and environmental damage through photocatalysis. In this work, we systematically investigated the structural stability of three all-inorganic lead halide perovskites (CsPbCl₃, CsPbBr₃, and CsPbI₃) towards ambient air (O₂); in particular, the role of light (photo-generated electrons and holes) in the perovskites' structural degradation was investigated using density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulation methods. We find that the adsorbed O₂ molecule is strongly activated on these perovskite surfaces even in the dark. Our results show that the presence of photo-generated electrons and holes increases the strength of O₂ adsorption; specifically, photo-generated electrons enhance the electrostatic interactions of these perovskite surfaces with O₂, resulting in a larger activation effect. AIMD simulations clearly show that adsorbed O₂ is readily activated on the surfaces of CsPbBr₃ and CsPbI₃, and Pb–O bonds form spontaneously in the presence of photo-generated electrons. Although the CsPbCl₃ perovskite surface has greater adsorption strength and activation effect towards O₂ in the presence of photo-generated electrons, it does not undergo light-induced structural degradation. Based on these results, we suggest that CsPbCl₃ perovskite can be a promising photocatalyst material.