Room-temperature synthesis, growth mechanisms and opto-electronic properties of organic–inorganic halide perovskite CH3NH3PbX3 (X = I, Br, and Cl) single crystals†
Single crystals of organic–inorganic halide perovskites are well needed in order to fully explore their potential in optoelectronic applications and to gain a fundamental understanding of their intrinsic properties. Previously, inverse temperature crystallization (ITC) was used to grow halide perovskite crystals at high temperatures (≈100 °C). Here, we develop an effective synthetic technique by which the CH3NH3PbX3 (X = I, Br, and Cl) crystals are grown in polar solvents at room temperature (except for CH3NH3PbI3 grown at 45 °C) in a relatively short time. A constant supersaturation during the crystal growth is created to produce large single crystals, which is achieved during room temperature crystallization (RTC) through controlled solvent evaporation. We investigate the effects of the temperature and supersaturation level on the nucleation kinetics of CH3NH3PbCl3 as an example, and propose and compare the different growth pathways. The crystal structural analysis, steady-state absorption, photoluminescence, and charge-transport properties demonstrate excellent long-term stability (over 2 years) of the RTC-grown CH3NH3PbX3 (X = Br, Cl) crystals against environmental degradation and moisture. The crystal optical properties are studied by polarized light microscopy, revealing birefringent ferroelastic domain structures characteristic of the tetragonal (X = Br) or orthorhombic (X = Cl) symmetry and high optical quality. This work presents a general strategy for designing, controlling, and optimizing the growth of high-quality halide perovskite crystals, which is an important step forward toward realizing high-end and stable optoelectronic devices such as nonlinear absorbers, photocatalyst, and micro-electromechanical actuators.