Facile Synthesis of Cu–In–S/ZnS Core/Shell Quantum Dots in 1-Dodecanethiol for Efficient Light-Emitting Diodes with an External Quantum Efficiency of 7.8%

CuInS2 quantum dots (QDs) are promising alternatives for user- and environment-friendly light-emitting diode (LED) applications, but the capping of electrically insulating ligands on QDs limits the device charge injection efficiency and results in poor LED performance. To solve the problem, in this work, we demonstrate the facile synthesis of Cu–In–S/ZnS (CIS/ZnS) core/shell QDs employing 1-dodecanethiol (DT) as the single ligand. The capping of QDs solely by DT not only enhances the colloidal stability of the QD ink by avoiding proton transfer between different kinds of ligands but also improves the electrical property of the QD films. By controlling the molar feed ratio of cations, the photoluminescence emission peak of the CIS/ZnS QDs is tunable from 530 to 710 nm. Because the QD surface chemistry is optimized, it becomes facile to perform QD surface modification for LED application. A QD LED prototype is fabricated using CIS/ZnS QDs as the emissive layer, which exhibits a maximum luminance of 4490 cd m–2 and a peak external quantum efficiency of 7.8%, boosting the best performance of CIS QD-based LEDs.