CsPbBr3 crystal nucleation and growth kinetics within acoustically levitated organic solution at room temperature

All inorganic perovskite CsPbBr 3 is regarded as a promising candidate for optoelectronic material applied in high-performance photodetectors. Herein, acoustic levitation technique was employed to study the crystallization process of the CsPbBr 3 solution, consisting of phase selection, crystal nucleation, and dynamic growth kinetics. It is found that the initial concentration and volume of the droplets closely relate to the evaporation rate and therefore influence the phase selection and crystallization mechanism. The crystallization of CsPbBr 3 crystals becomes dominant under acoustic levitation. With the increase of droplet volume and the solution concentration, the primary phase transforms from CsPbBr 3 to PbBr 2 ·DMSO crystal. The nucleus always forms near the surface at the equator of acoustically levitated droplets, which is attributed to the enhanced evaporation rate by acoustic streaming. The CsPbBr 3 crystals always grow in two patterns: free growth and adherent growth, which are characterized by faceted dendrites. The maximum growth velocity of CsPbBr 3 crystals reaches 0.34 μm·s -1 and 0.57 μm·s -1 in the two growth patterns, which is at least ten times larger than that by the conventional crystallization method. The formation of competitive PbBr 2 ·DMSO crystals can be modulated by controlling the droplet volume and the crystallization time. The acoustic levitation technique provides a unique way for investigating the crystallization of CsPbBr 3 solutions with containerless environment and improving the crystal quality by active modulations.