Performance Enhancement of All-Inorganic Quantum Dot Light-Emitting Diodes via Surface Modification of Nickel Oxide Nanoparticles Hole Transport Layer

All-inorganic quantum dot light-emitting diodes (QLEDs) show promise for advanced lighting and display due to their superior advantage in stability. However, all-inorganic QLEDs suffer from low efficiency because of the exciton quenching and inefficient hole transport from the inorganic hole transport layer (HTL) to QDs. Herein, we demonstrate an efficient all-inorganic QLED with NiO nanoparticles (NPs) HTL modified by 11-mercaptoundecanoic acid (MUA). The MUA can passivate the defects of NiO and suppress the exciton quenching. Moreover, the declined valence band level of modified NiO could facilitate the hole transport, promoting the charge balance. In addition, the surface engineering improves the quality of the NiO film, leading to the decrease of current leakage. As a result, the maximum current efficiency and external quantum efficiency (EQE) of our QLEDs achieve 5.50 cd/A and 1.28%, respectively, exhibiting an enhancement of 4.5- and 1.72-fold, respectively. Meanwhile, the stability of the device is drastically improved by more than 20-fold after modifying the NiO with MUA. The strategy offers a pathway to enhance the efficiency and the operation lifetime of all-inorganic QLEDs.