Combined Purification and Crystal Growth of CsPbBr3 by Modified Zone Refining

Abstract

The all-inorganic semiconducting perovskite Cesium Lead Bromide, CsPbBr3, exhibits promising properties for ionizing radiation detection applications. In this work, polycrystalline CsPbBr3 was synthesized from the melt of binary compounds CsBr and PbBr2. Moisture and oxides in the synthesized CsPbBr3 compounds were removed by a reduction process under hydrogen. The CsPbBr3 materials were purified and grown into high-quality single crystals via a modified zone refining process. The single-crystal samples obtained from the combined zone-refining/crystal growth process exhibited total trace impurity levels below 1 ppm (w.t.). Obtained single crystals exhibited an electrical resistivity within a range of 10^8~10^9 Ω·cm. Stoichiometry imbalance was observed in the CsPbBr3 crystal growth. Around 1% Cs deficiency was observed in all the samples, despite different ratios between the starting materials of PbBr2 and CsBr. The positive impact of excess PbBr2 in starting materials was also revealed. With a slight excess Pb (2%), CsPbBr3 single crystals displayed significantly higher photosensitivity compared to the stoichiometric or excess Cs samples.