Passivating defects in ZnO electron transport layer for enhancing performance of red InP-based quantum dot light-emitting diodes.

• Mg-doped and ZnMgo-coated shell of ZnO NPs were synthesized using the sol-gel method. • The performance of QLED devices using Mg-doped ZnO NPs as ETLs was significantly improved, achieving a maximum EQE of 6.0 % and a maximum current efficiency of 8.2 cd A−1. • The device performance was further improved by utilizing Mg-doped and ZnMgO-coated ZnO NPs as ETL, which achieved a maximum EQE of 9.0 % and a maximum current efficiency of 11.5 cd A−1. ZnO nanoparticles (NPs) are considered the most promising materials for electron transport layer (ETL) in quantum dot light-emitting diodes (QLEDs). Herein, we employed a synergistic strategy of Mg doping and ZnMgO shell coating to modify the defect states and energy levels of ZnO NPs. Mg doping mitigated the exciton luminescence quenching caused by charge transfer. A ZnMgO shell was also applied to coat the Mg-doped ZnO (ZMO) NPs to passivate surface oxygen defects further. Consequently, QLEDs utilizing ZMO@ZnMgO ETL demonstrate external quantum efficiency and maximum current efficiency of 9.0 % and 11.5 cd A−1. This work shows an effective defect passivation strategy to enhance the performance of red-emitting InP-based QLEDs. A coordinated strategy of Mg doping and ZnMgO shell coating was employed to modify the defect states and energy levels of ZnO nanoparticles to improve the performance of red-emitting InP-based QLEDs. With Mg doping, the conduction band minimum of ZnO NPs shifts upward, which reduces the electron accumulation at the QD/ZnO interface and mitigates exciton luminescence quenching caused by spontaneous charge transfer at the interface. Additionally, a ZnMgO shell was applied to coat the Mg-doped ZnO (ZMO) NPs to passivate surface oxygen defects and improve the luminescence efficiency of the QLED devices. As a result, QLEDs utilizing ZMO@ZnMgO ETLs demonstrate an external quantum efficiency of 9.0 % and a maximum current efficiency of 11.5 cd A−1, which are approximately 2.4-fold higher than those of the devices with ZnO ETLs. [Display omitted] [ABSTRACT FROM AUTHOR]