Steric Mixed-Cation 2D Perovskite as a Methylammonium Locker to Stabilize MAPbI3

The reduced dimension perovskite including 2D perovskites are one of the most promising strategies to stabilize lead halide perovskite. A mixed-cation 2D perovskite based on a steric phenyltrimethylammonium (PTA) cation is presented. The PTA-MA mixed-cation 2D perovskite of PTAMAPbI(4) can be formed on the surface of MAPbI(3) (PTAI-MAPbI(3)) by controllable PTAI intercalation by either spin coating or soaking. The PTAMAPbI(4) capping layer can not only passivate PTAI-MAPbI(3) perovskite but also act as MA(+) locker to inhibit MAI extraction and significantly enhance the stability. The highly stable PTAI-MAPbI(3) based perovskite solar cells exhibit a reproducible photovoltaic performance with a champion PCE of 21.16 %. Such unencapsulated devices retain 93 % of initial efficiency after 500 h continuous illumination. This steric mixed-cation 2D perovskite as MA(+) locker to stabilize the MAPbI(3) is a promising strategy to design stable and high-performance hybrid lead halide perovskites.