Controlled synthesis and photoluminescence study of blue-emitting Cs3Bi2Br9 nanocrystals prepared by the ligand-assisted reprecipitation (LARP) method

Cs3Bi2Br9 perovskite nanocrystals (PNCs) offer promising light-emitting properties due to a tunable bandgap, excellent luminescence, and low-cost fabrication. Multiple synthesis methods to produce Cs3Bi2Br9 have been investigated in recent years, with discrepancies in their reported photoluminescent properties, and low quantum yields. In this study, the ligand-assisted reprecipitation (LARP) method was adopted to synthesize Cs3Bi2Br9 PNCs using dimethyl sulfoxide and chloroform as the solvent and anti-solvent, respectively. LARP provided a simple approach to produce Cs3Bi2Br9 PNCs with the freedom to vary parameters such as temperature, solvents, and ligands. The use of dimethyl sulfoxide allowed for the rapid dissolution of the precursors, thereby decreasing the fabrication time, while chloroform resulted in a high product yield. The synthesis temperature was demonstrated as a significant parameter that influenced the direct and indirect bandgap nature of the PNCs. Oleylamine and oleic acid were used as ligands in the LARP synthesis. By varying the concentration of oleic acid, the bandgap of the Cs3Bi2Br9 NCs changed from 3.85 eV to 3.29 eV. Oleic acid concentration demonstrated influence over the crystal structure of the Cs3Bi2Br9 NCs. The photoluminescence quantum yield (PLQY) of the optimum PNCs was 62%.