A mechanistic investigation of moisture-induced degradation of methylammonium lead iodide

We performed in situ x-ray diffraction (XRD) experiments on an inorganic-organic hybrid perovskite, CH3NH3PbI3 (MAPbI3), during its interaction with moisture to understand the degradation mechanism. Although the degradation of inorganic-organic hybrid perovskite is an important factor hampering their development as solar cell materials, understanding of the degradation process is currently limited. The moisture-induced degradation mechanism was revealed by the temperature dependence of the in situ XRD pattern sequences and first-principles calculations based on the nudged elastic band method. The combination of experimental and computational data suggests that the MAPbI3 crystal spontaneously changes into the MAPbI3 mono-hydrate crystal once water molecules activated with an energy of more than ∼0.6 eV penetrate the (100) outer surface of the MAPbI3 lattice. These findings have important implications for the development of more robust inorganic-organic hybrid perovskites as light absorbing layers in solar cells and other applications.