First-principles Study on Water Dissociation in Grain Boundary of MAPbI₃ Perovskite

Using first-principles calculation, we investigate water-dissociation dynamics in a Σ5 tilt grain boundary (GB) of Methyl-Ammonium Lead Triiodide (MAPbI3) perovskite. We find that the water dissociation process undergoes with two-step reaction at the GB: one of H ions of a water molecule that segregates into the GB is dissociated, migrates along the GB, and is attracted by an N atom in the MAPbI3, following the H-ion release from the ammonium. The process thereby generates OH^- ion and, in turn, leads to possible initiation of the degradation for crystallinity in the perovskite.