Growth of Hybrid Perovskite Crystals from CH 3 NH 3 PbI 3- x Cl x Solutions Subjected to Constant Solvent Evaporation Rates.

In this work, we subjected hybrid lead-mixed halide perovskite (CH 3 NH 3 PbI 3- x Cl x ) precursor inks to different solvent evaporation rates in order to facilitate the nucleation and growth of perovskite crystals. By controlling the temperature of perovskite solutions placed within open-air rings in precise volumes, we established control over the rate of solvent evaporation and, thus, over both the growth rate and the shape of perovskite crystals. Direct utilization of diluted lead-mixed halide perovskites solutions allowed us to control the nucleation and to favor the growth of only a low number of perovskite crystals. Such crystals exhibited a clear sixfold symmetry. While crystals formed at a lower range of temperatures (40-60 °C) exhibited a more compact dendritic shape, the crystals grown at a higher temperature range (80-110 °C) displayed a fractal dendritic morphology.