Water in Hybrid Perovskites: Bulk MAPbI3 Degradation via Super-Hydrous State
Journal Article - Open Access
PENNSYLVANIA UNIV PHILADELPHIA PHILADELPHIA United States
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Here, first-principles density functional theory calculations are presented which reveal how water incorporation in hybrid halide perovskiteCH3NH3PbI3 MAPbI3 catalyzes the phase transition to the CH3NH3PbI3.H2O edge-sharing monohydrate colorless phase, eliminatingits favorable photovoltaic properties. First, fundamental chemical and electrostatic interactions between water and each componentof MAPbI3 are analyzed, demonstrating their dependence on water concentration. Second, the energetics of incorporated water is explored,leading to the discovery of spontaneous phase segregation into dry regions and regions with more than one water per formula unittermedthe super-hydrous state. Third, the properties of the super-hydrous state are analyzed, including the acceleration of octahedron breaking andrearrangement by the high water density. This reveals the phase transformation to be a bulk process, initiated at the super-hydrous regions.This paper concludes with a discussion of how this super-hydrous model explains disparate recent experimental observations concerning thewater-induced transition from black perovskite to edge-sharing PbI2 yellow phase.
- Physical Chemistry
- Quantum Theory and Relativity