Theoretical Investigation of Organohalide Perovskite Degradation in Water

Abstract

Methylammonium lead iodide (CH3NH3PbI3) is an extensively used organic-inorganic perovskite material with a remarkable potential for solar energy conversion. Despite its high photovoltaic efficiency, it suffers from fast degradation in humid air atmospheric working environments. Low stability of CH3NH3PbI3 solar cells in humid air environments is a serious drawback, severely limiting their practical application. Protecting organohalide perovskite thin films from water and ambient humidity represents a paramount challenge, in which the interfacial interactions between CH3NH3PbI3 surface and water molecules need to be understood thoroughly. Here, we present ab initio molecular dynamics simulations aimed at investigating interfacial interactions between the CH3NH3PbI3 perovskite of different surfaces and water molecules. We harness enhanced free-energy sampling techniques to simulate CH3NH3PbI3 degradation with explicit treatment of water molecules to examine the degradation kinetics. The degradation energetics from different CH3NH3PbI3 surfaces along with the effect of various type of defects in the material are also explored. Our findings add a comprehensive mechanistic understanding to the state of knowledge of CH3NH3PbI3 degradation mechanisms in humid air. The presentation will close with a discussion of similar stability predictions on other organohalide perovskite materials.