Bismuth Enhances the Stability of CH3NH3PbI3 (MAPI) Perovskite under High Humidity

Methylammonium lead iodide (CH3NH3PbI3, MAPI) is a high-performance solar cell material but lacks stability in the presence of humidity. Addition of a few percent bismuth (Bi) as a trivalent cation substitute for Pb (i.e., MAP­(Bi)­I) leads to enhanced stability under high (90%) relative humidity (RH). At moderate humidity (60% RH), however, MAP­(Bi)I degrades more rapidly than MAPI. Bi incorporation into MAPI either stabilizes or destabilizes the two hydration products, MAPI·H2O and PbI2, depending on the amount of humidity in the environment.