Optimization of the Growth Conditions for High Quality CH3NH3PbBr3 Hybrid Perovskite Single Crystals

Methylammonium lead tribromide (CH3NH3PbBr3) single crystals have gained growing attention in the past few years due to their use as a model material to investigate relevant intrinsic perovskite properties and for their potential applications for radiation detection. Their study has been facilitated by the ease and speed of fabrication of millimetric single crystals through a simple protocol of unseeded inverse temperature crystallization (ITC). In this study, we show that such growing conditions suffer from both insufficient reproducibility regarding crystal quality and low yield of single crystal obtention. In particular, we observed that more than half of the crystals obtained by this technique are polycrystals. The structural defects of the rest of the single crystals obtained have been characterized by cross polarized light, surface chemical etching to reveal dislocations, X-ray diffraction, ICP-MS, and H NMR. The results reveal a strong variability of crystals regarding internal strains and dislocation densities. Such defects can further severely impact the electronic transport properties of these materials. A more robust and reproducible protocol is proposed based on seeded growth combined with appropriate temperature profile selected from continuous crystal growth monitoring. A clear improvement in crystal quality is reached with higher transparency, minimized internal strains, and a low dislocation density in the range of 104–105 cm–2.