Ligand regulated selective synthesis of Cs4PbCl6 microcrystals in microemulsion and their cathodoluminescence

In recent years, all-inorganic perovskite semiconductor CsPbCl3 is widely studied because of its excellent optical and electronic properties, but its derivative Cs4PbCl6, which possesses a wider band gap, is seldom studied due to the challenging synthesis. In this work, we demonstrate a selective synthesis method for Cs4PbCl6 and CsPbCl3 in microemulsion regulated by the ligand concentration of n-octylamine. When the concentration is sufficiently high, the products are regular hexagonal Cs4PbCl6 microcrystal in sizes of 1-2 mu m; when the concentration is sufficiently low, the products are rectangular plate-shaped CsPbCl3 nanocrystals in sizes of 200-800 nm; and when the concentration is moderate, the products are their mixtures. Cathodoluminescence spectrum of a single particle of Cs4PbCl6 is measured. The change of Pb2+ solubility regulated by the ligand concentration is mainly responsible for the selective synthesis. This method applies for the synthesis of Cs4PbBr6.