ZnMgO Nanoparticles via Ultrasonic-Assisted Synthesis for Electron Transport Layer in InP-Based QD-LEDs

Ultrasonic-assisted synthesis was performed to effectively dope ZnO nanoparticles (NPs) with Mg for use in colloidal quantum dot light-emitting diodes (QD-LEDs). When ZnMgO NPs were synthesized through ultrasonic synthesis, higher Mg doping concentrations could be achieved, despite the smaller sizes of NPs than those synthesized using conventional heating methods. Additionally, to improve the stability of the electron transport layer (ETL) in the QD-LED structure, a ZnO/Mg(OH)₂ (s-ZnO/Mg) structure was synthesized by first synthesizing ZnO via ultrasonication, followed by Mg treatment. When s-ZnO/Mg was applied to a green-emitting InP QD-LED device, the brightness and efficiency of the device were significantly improved. Specifically, the green-emitting InP QD-LED device exhibited a luminance of 25,396 cd/m² and an external quantum efficiency (EQE) of 2.51%. These results represent a 1.32- and 1.43-fold increase in luminance and EQE, respectively, compared to the QD-LED device with ultrasound-assisted ZnO. During the lifetime measurement of the QD-LED device, it required approximately 43.0 h to reach half its brightness at a luminance of 2,200 cd/m², which is a 1.69-fold increase compared to the QD-LED device with ZnO.