Inverted green quantum-dot light-emitting diode with sputtered ZnO as the electron transporting layer

Recently, Quantum-dot light-emitting diode (QLED) has attracted much attention due to narrow electroluminescence (EL) spectra, low driving voltage, tunable emission colors and simple fabrication. In conventional QLED structure, inorganic zinc oxide (ZnO) nanoparticles was usually used as electron transporting layer material by spin-coating. However, defects in solution-processed ZnO film may quench quantum dot (QD) emission and increase the driving voltage. In this study, we fabricated ZnO by sputtering process with the inverted structure. Compared to the QLED with solution-processed ZnO as the ETL, driving voltage of the device with sputtered-ZnO as the ETL significantly decreased from 7.04 V to 2.95 at current density of 20 mA/cm2, while the current efficiency remained at 11.46 and 11.70 cd/A at current density of 80 mA/cm2.