Precipitation-Dissolution Phase Diagrams of Lead Halide Perovskites in Solutions for Single Crystallization in Capillaries

Organic-inorganic halide perovskite materials have attracted significant attention in the field of optoelectronics, and their single crystals, in particular, exhibit high carrier mobility. However, because single crystals were typically grown from highly polar donor solvents, the crystallization process was complicated by the formation of complexes, solvated crystals, and polymorphs. Despite these complexities, many studies have relied on empirical trial-and-error approaches, without systematically integrating the crystallization process into crystal engineering through phase diagrams. In this study, we constructed a phase diagram of methylammonium lead iodide perovskite and clarified its solubility and precipitation curves. From van't Hoff analysis, we determined the enthalpy and entropy of dissolution. Based on the supersaturation conditions obtained from the precipitation and solubility curves, we successfully grew single crystals. These insights are expected to provide important guidance for the fabrication of solar cells, photodetectors, and integrated devices.