Аннотация:Various phenomena and techniques canbe explained by ambient temperature iondiffusion in halide perovskites. It is shownthat the really fast diffusers are protons,rather than halides, using deuterium isotopetracing in MAPbI3, MAPbBr3, andFAPbBr3, and other methods, find waterto be critical for proton diffusion, and thatalready reported results are compatiblewith this new insight