Lead Halide Perovskites: Size-Dependent Properties and Photostability

Lead halide perovskite [APbX₃; A=CH₃NH₃⁺, CH(NH₂)₂⁺, Cs⁺; X=Cl^-, Br^-, I^-] thin films and colloidal nanocrystals (NCs) have taken a dominant position in the pursuit for next-generation photovoltaic and light-emitting devices. Improved knowledge of their fundamental properties and photostability are still required to realize large-scale commercialization. In particular, the origin of universally observed size-dependent Stokes shifts in perovskite NCs and the precise crystal structure assumed by CsPbBr₃ NCs remain of fundamental interest. In terms of photostability, uniformly mixed halide perovskites [e.g., APb(I_1-xBr_x)₃] thin films and NCs suffer dramatic changes to their underlying optical and structural properties during continuous visible or ultraviolet illumination. Elucidating the role played by defects (e.g. halide vacancies) as well as other photochemical processes (e.g. photoinduced I₂ sublimation) provides critical mechanistic insight into this phenomenon. Only by developing a truly comprehensive understanding of their fundamental properties and photostability can lead halide perovskites be successfully implemented into working devices.