Interactions between H2O and lead halide perovskites: Recent progress and applications

The synthesis of lead halide perovskites typically involves airborne H2O molecules, which can exist in gaseous, liquid, or solid forms. Generally, H2O is considered harmful to perovskite materials and devices, causing alarm at the mere mention of it. However, this pair of "old friends"always demonstrate a complex "love-hate"relationship. In some cases, H2O can positively affect perovskites, endowing them with excellent properties. A comprehensive understanding of their interactions with H2O will be crucial for the commercialization of perovskites. Here, we summarize recent progress on the interactions between H2O and lead halide perovskites, focusing primarily on three areas: growth regulation, crystallization regulation, and interactions with already-formed perovskites. These interactions allow perovskites to be widely used in a variety of fields, including light-emitting diodes, solar cells, photodetectors, anti- counterfeiting, and bioimaging. Finally, we discuss the challenges and prospects of green synthesis, interfacial chemistry, and precursor solution chemistry.