Water-passivated ZnMgO nanoparticles for blue quantum dot light-emitting diodes

Abstract

It is known that the use of magnesium doped zinc oxide (ZnMgO) nanoparticles results in a serious exciton quenching and unbalanced charge carriers inside the quantum dot light-emitting diodes (QLEDs), leading to an inferior device performance (particularly in blue QLEDs). Herein, we use water as a passivation agent to fix the interface between QDs and ZnMgO. On the one hand, the oxygen atoms in water could contact with metal atoms through an electrostatic interaction to fill the oxygen vacancies on the surface of ZnMgO and remove the surface defects so that the excitons formed inside QDs are less quenched. On the other hand, it slightly decreases the electron transport from ZnMgO to QDs, resulting in much more balanced holes and electrons inside the QD emissive layers. Therefore, the blue QLEDs made by the water-passivated ZnMgO exihibit an improved external quantum efficiency (EQE) of 11.0% and luminance of over 20 000 cd m-2 at 6 V, which is significantly higher than those of blue QLEDs made by pristine ZnMgO. To further understand the improved performance among the blue QLEDs, photoluminescence (PL) spectroscopy, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) were used to characterize these water-passivated ZnMgO nanoparticles.