Ligand-Exchange-Ready CuInS₂/ZnS Quantum Dots via Surface-Ligand Composition Control for Film-Type Display Devices

Quantum dots (QDs) are promising material that regularly requires ligand exchange for application in film-type display devices. However, the photoluminescence quantum yield (PLQY) and ligand exchangeability of the QDs are often incompatible with each other because strongly bonded ligands, which easily grant high PLQY, require more energy to be changed to other ligands. Here we present CuInS₂/ZnS QDs comprising both high ligand exchangeability and PLQY through a simple mixed-ligand synthesis approach to control the composition of the surface ligands. The QDs were able to maintain both beneficial traits of thiol- and amine-based ligands, which are high PLQY and ligand exchangeability, respectively. The analysis showed that the resulting QDs that contain combined ligand composition have PLQYs reaching up to 90% of the QDs with only the thiol-based ligand while maintaining a certain portion of the amine-based ligand as intended to comprise facile ligand exchangeability. Furthermore, it was found that the PLQY of the QDs was able to be augmented even further by the ligand exchange. These findings are expected to greatly simplify the fabrication of efficient film-type display devices.