Crystallization of CH3NH3PbI3−xBrx perovskite from micro-droplets of lead acetate precursor solution

Abstract

The physical properties of organic–inorganic hybrid perovskite materials are greatly influenced by their composition, crystallinity, and morphology. Here, we investigate the growth of CH₃NH₃PbI_3−xBr_x perovskite from micro-droplets of a methylammonium iodide/lead acetate/dimethylformamide precursor solution added with different concentrations of PbBr₂, which helps to control the morphology and crystallinity of the perovskite film. We find that both perovskite and its intermediate containing an acetate group growing from the micro-droplets. By adding some PbBr₂, there is a tendency to form cubic perovskite crystals due to partial substitution of iodine with bromide. There is composition segregation when the crystals grow freely from the droplets. Smooth and uniform CH₃NH₃PbI_3−xBr_x perovskite films with a tunable band gap are thus fabricated from the precursor solution added with PbBr₂.