Large-Area Quantum Dot Light-Emitting Diodes Employing Sputtered Zn_0.85Mg_0.15O Electron Transport Material

We report a large-area quantum dot light-emitting diode (QLED) with sputtered Zn_0.85Mg_0.15O (ZMO) as an electron transport layer (ETL). Uniform ZMO is applied as ETL of the inverted structured QLED and the adjustment of Ar/O₂ ratio on device characteristics is studied in detail. Compared to pristine ZMO, ZMOs with O₂ gas are found to be beneficial to the charge balance in the emitting layer of QLEDs mainly by their upshifted conduction band minimum, which in turn limits an electron injection. Additionally, it is found that oxygen vacancies in the ZMO, acting as the exciton quenching sites, are responsible for the device stability. QLEDs with 6:1 ZMO produce a maximum luminance of 136,257 cd/m² and external quantum efficiency of 5.15%, which are the best device performances to date among QLEDs with sputtered ETLs. These results indicate that the sputtered ZMO shows great promise for use as an inorganic ETL for future large-area QLEDs.