Room-Temperature Synthesis and Tuning Optical Properties of CsPbBr₃ Nanocrystals via Ligand-Assisted Reprecipitation

Perovskite nanocrystals (NCs) have attracted significant attention owing to their unique properties such as high photoluminescence (PL) quantum yield and color tunability. They can be easily synthesized at room temperature via ligand-assisted reprecipitation (LARP). The bandgap energy of the NCs could be tuned by controlling the growth conditions of the LARP method. Therefore, we synthesized the CsPbBr₃ perovskite NCs with the precursor dissolution time sequentially increased (10, 15, 20, and 25 min) so as to increase the precursor concentration in the solution. The PL spectra showed that the PL peak positions of the samples shifted from 509.5 to 518.0 nm with increasing dissolution time owing to the decreased ligand-to-precursor ratio. The full-width at half-maximum and Stokes shift decreased with increasing dissolution time because of size-defocusing and the confined hole states near the valance band, respectively. In addition, the bandgap and size estimations were investigated using the Tauc plot and effective mass approximation. With increasing the dissolution time, the estimated bandgap of the NCs varied from 2.41 to 2.37 eV, while the calculated size increased from 5.7 to 6.6 nm.