An ab-initio study of water interactions in the hybrid perovskite MAPbI₃

Hybrid (organic-inorganic) perovskites have recently received great attention as candidates for commercially viable and efficient conversion of solar energy. Nevertheless, the performance and stability of these materials gets affected by water and moisture in the environment. Here, using density functional theory (DFT) simulations, and taking MAPbI₃ as our case study, we investigate the nature of water interactions in hybrid perovskite MAPbI₃. Changing water concentration over 2 orders of magnitude, we study the process of water infiltration and the surface and bulk chemistry that follows and leads to first reversible, and then irreversible changes to the material’s structure. We discuss, based on electronic-structure analyses, how water changes the optical properties of the material in different concentrations. Such understanding of the nature of water--hybrid-perovskite interactions, can then be used to design better and more stable solar cells.