Zero-Dimensional Hybrid Organic–Inorganic Lead Halides and Their Post-Synthesis Reversible Transformation into Three-Dimensional Perovskites

Zero-dimensional (0D) mixed-halide hybrid organic–inorganic MA4PbX6·2H2O (MA = CH3NH3+; X = Br1 – xIx with 0 < x < 1) has been synthesized by a solvent-free mechanochemical approach. It has been shown that this 0D phase with sharp absorption features in the near-UV is a hydrated structure, which can be reversibly transformed into the three-dimensional perovskite phase MAPbX3 by simple thermal annealing (dehydration) in air. This work reveals a new approach to hybrid organic–inorganic perovskites and related 0D structures, which have so far only been thoroughly studied for the inorganic Cs4PbX6 compounds.