Suppression of blinking in single CsPbBr₃ perovskite nanocrystals through surface ligand exchange

Photoluminescence blinking in individual semiconducting and perovskite quantum dots reflects reduced emission quantum yield and represents an obstacle towards quantum dot applications. One of the origins of blinking is the presence of surface structural defects that can function as charge traps. To reduce the defects the surface can be modified by, e.g., covering with ligands that are more strongly bound to the surface. Here, we report exchange of ligands on the CsPbBr₃ perovskite nanocrystal surface and the effect of the exchange on photoluminescence blinking. Replacement of the oleic acid and oleylamine ligands which are used in the synthesis process with quaternary amine ligands leads to substantial increase of photoluminescence quantum yield. On single particle level this is reflected by significantly improved blinking characteristics. Statistical analysis using the probability density function shows that the ligand exchange leads to longer duration of ON-times and shorter OFF-times, as well as to the presence of a higher fraction of ON-time intervals. These characteristics are not affected by sample aging within three weeks. On the contrary, storage of the samples in solution for one-to-two weeks leads to further improvement of the ON-time interval fraction statistics.