Insight into the Interaction between Perovskite and Water via In Situ PL Measurement

Contrary to widely held view that water induces negative effect on lead halide perovskites, publications on active role of water in photoluminescence (PL) and stability of perovskites have been emerged recently. Until now, comprehensively understanding the interaction between perovskite and water is absolutely necessary for its highly correlation with the practical application and remains a significant challenge. In this study, we utilize in situ PL measurement, ex situ transmission electron microscopy, UV–vis spectroscopy and X-ray photoelectron spectroscopy to track and reveal the interaction of perovskite with water. For the organic-inorganic lead bromide perovskite, water induces amorphization, degradation of MAPbBr3, as well as formation of PbBrOH. As-obtained MAPbBr3@PbBrOH composites exhibit high PL quantum yield (QY) of 41.8–57.0% and robust water stability for the protection from PbBrOH. For cesium lead bromide perovskite, water facilitates the phase transition from non-luminescent Cs4PbBr6 to luminescent CsPbBr3, and could also instigate the formation of PbBrOH. However, the water-induced Ostwald maturation of CsPbBr3 and structure defects brought by the phase transition ultimately lead to the production of large CsPbBr3 crystals or CsPbBr3@PbBrOH composites with ultralow PLQY. This work provides valuable insights into the interaction between perovskite and water, and holds important implications for comprehending the instability of lead halide perovskites.