Effect of crystal structures on the stability of CH3NH3PbI3 under humidity environment

Abstract The efficiency of organic-inorganic hybrid perovskite (CH 3 NH 3 PbI 3, MAPbI 3 ) solar cells has been dramatically increased from 3.8% to 20.1% in the past five years, which is close to its theoretical limit. Nevertheless, the stability of perovskite solar cells remains a major hurdle for its commercialization. Here, we investigated the morphology and structure of MAPbI 3 films with different preparation conditions, and reported the existence of orthorhombic structure in tetragonal MAPbI 3 cuboids at room temperature. More interestingly, a special orthorhombic-to-tetragonal phase transition could lead to intensity oscillations in the time evolution of photoluminescence (PL), and increased the films stability in a high humidity (∼50%) environment. Furthermore, we used the films to prepare photovoltaic devices with a half-life over 200 h, and showed the potential of the phase transition to improve the lifetime and practical application for perovskite solar cells.