Optimization of ZnO Nano Particles Preparation and Its Performance as Electron Transfer Layer in Quantum Light-Emitting Diode

In this paper, different diameters ZnO Nano Particles (ZnO NPs) are prepared through wet chemistry method. The size effects on Quantum light-emitting diodes (QLED) performance are investigated. In addition, the influences of reaction temperature, reaction time and reactant ratio on ZnO size and performance of QLED are also studied. Transmission electron microscope (TEM), Ultraviolet-Visible spectroscopy (UV-Vis) absorption spectra and photoluminescence (PL) spectra are employed to analyze the influence of preparation conditions on optical properties of the ZnO NPs packaged QLED. The results show that 2.5 nm ZnO NPs can be obtained at 25 °C for 6 hours when the Zn²+:OH^- ratio is 1:1. In comparison to the 5 nm ZnO QLED, the EQE of the 2.5 nm ZnO QLED has increased from 1% to 7.8%, and the brightness has increased from 8000 to 13000 cd/m². When ZnO NPs solution concentration is 30 mg/ml and spin speed is 4000 rpm, the optimal turn-on voltages and luminous intensity of QLED can also be attained.