Modified Zinc Magnesium Oxide for Optimal Charge-Injection Balance in InP Quantum Dot Light-Emitting Diodes

Balanced charge injection into the emissive layer is a prerequisite for achieving highly efficient quantum dot light-emitting diodes (QLEDs). The similar energy distribution of charge transport layers and indium phosphide (InP) quantum dots (QDs) facilitates excess electron injection to the InP QD layer. In this study, magnesium-doped ZnO nanoparticles (ZMO NPs) are modified to suppress the electron injection to the InP QD layer. Particularly, hydroxyl groups are effectively replaced by electrically stable states through the passivation of ZMO NPs, retarding electron injection through the ZMO NP layer. The modified ZMO-NP-based InP QLEDs exhibit a maximum external quantum efficiency of 9.6% with a substantially enhanced operational lifetime compared with that of devices made with unmodified ZMO NPs.