Highly efficient and low turn-on voltage quantum-dot light-emitting diodes using a ZnMgO/ZnO double electron transport layer

A ZnMgO and ZnO double-layered structure was prepared to create a stepwise interfacial electronic structure to improve the electron-injection and electron-transport behaviors in quantum-dot light-emitting diodes (QLEDs). The current density of the electron-only device (EOD) with ZnMgO/ZnO was higher than that of the EOD with only ZnMgO. The detailed QLED interfacial electronic structure was measured using X-ray and ultraviolet photoelectron spectroscopy. A stepwise interfacial electronic structure for electron injection and electron transport was observed connecting the aluminum cathode to the ZnMgO conduction band minimum (CBM) via the ZnO CBM. The QLEDs with the ZnMgO/ZnO double electron transport layer showed an improved performance, with a maximum luminance and current efficiency of 90,892 cd m−2 and 19.2 cd A−1, respectively. Moreover, the turn-on voltage of the device was significantly reduced to 2.6 V due to the stepwise interfacial electronic structure between the aluminum cathode and ZnMgO CBM. This research provides a useful method for developing highly efficient and low turn-on voltage QLEDs using a ZnMgO/ZnO double ETL for next-generation display.