Performance Enhancement of Quantum Dot Light-Emitting Diodes via Surface Modification of the Emitting Layer

CdSe-based quantum dots (QDs) have increasingly become important QDs for emerging display material because of their suitable bandgap, controllable size, and high PLQY. However, there are still many problems with CdSe QD films, including severe fluorescence quenching and low conductivity. Herein, we replace the long insulated oleic acid ligand with the shorter thiol ligand to enhance the mobility of charge carriers. It was found that the QDs with octanethiol in a quantum dot light-emitting diode (QLED) exhibited higher conductivity and lower turn-on voltage. Moreover, the defects on the surface of the QD layer were effectively passivated by adding a thin layer of cesium carbonate, and the radiation recombination of the quantum dot light-emitting layer was also significantly improved. It was evident that the performance of the optimized QLED device was improved with a peak luminance of 166 300–294 500 cd/m2 and a peak current efficiency of 10–32 cd/A. Thus, the current work provides two ways to optimize QD films and proposes a method to improve the performance of QLEDs.