Silver thiocyanate treatment-induced enhancement of photoluminescence efficiency of CsPbBr₃ perovskite quantum dots

Metal halide perovskite nanostructures have received much attention for many optoelectronic devices, such as solar cells, light-emitting diodes, photodetectors, and sensors due to their sharp emission spectra and adjustable wide optical bandgap. However, low emission efficiency and stability still impede their development and application. This paper reports a facile surface modification of the CsPbBr₃ quantum dots (QDs) to enhance the optical performance using a silver thiocyanate (AgSCN) additive. Structural and chemical investigations show that the QD morphology and size do not change significantly, while the SCN^– anion is incorporated into the CsPbBr₃ QDs as a function of AgSCN loading. In addition, the SCN^– anion interacts with Pb²⁺ in the CsPbBr₃ QDs, which indicates that the SCN^– anion fills out the Br^– anion vacancy site or substitutes the Br^- anion without significantly affecting the ligand configuration. Therefore, the photoluminescence (PL) intensity and stability of the AgSCN-treated CsPbBr₃ QDs are improved compared to the pristine one, because the AgSCN plays a critical role in recovering the appropriate surface stoichiometry and eliminating the defective surface states.