A Rapid and Robust Light-and-Solution-Triggered In Situ Crafting of Organic Passivating Membrane over Metal Halide Perovskites for Markedly Improved Stability and Photocatalysis

Despite intriguing optoelectronic attributes in solar cells, light-emitting diodes, and photocatalysis, the instability of organic-inorganic perovskites poises a grand challenge for long-term applications. Herein, we report a simple yet robust strategy via light-and-solution treatment to create an organic membrane that effectively passivates CH3NH3PbI3 (MAPbI3). Specifically, the restructuring of MA+ is observed on MAPbI3 in aqueous hydrogen iodide. HIO3 molecules are generated via the reaction between water and I2 induced by photocatalysis when MAPbI3 is illuminated. The hydrogen bonding between HIO3 molecules at different perovskite particles not only directs the creeplike growth of perovskite particles but also in situ forms a passivating layer firmly anchoring on the perovskite surface with hydrophilic -NH3+ groups tethering to perovskites and hydrophobic -CH3 moieties exposed to air. Intriguingly, such MA+ film greatly improves the stability of perovskites against moisture as well as their crystal quality, considerably enhancing the photocatalytic hydrogen evolution rate.