Microspacing In-Air Sublimation Growth of Thickness-Controllable Lead Halide Crystal and the Morphology Evolution in Conversion to Perovskite

The formation process of hybrid perovskites affects the morphology, performance, and stability of the materials to a large extent. This work takes the preparation of a prototypical perovskite, methylammonium lead iodide (MAPbI3) from vapor conversion to illustrate the effect of reaction conditions. First, we applied our recently invented microspacing in-air sublimation (MAS) to grow PbI2 crystals with thicknesses ranging from several to hundreds of nanometers. The PbI2 single crystals were employed to investigate the conversion to MAPbI3. This proved that vapor conversion is indeed a single-crystalline-to-polycrystalline process, following a deconstruction–reconstruction mechanism. Both the crystal thickness and activation temperature greatly affect the revolution, while the morphology of the formed perovskite is dictated by the thickness of the precursor crystal. Clarification of the intrinsic and exerted factors on the conversion process is conducive to a deep understanding of the perovskite formation process.