Efficient inverted top-emitting organic light-emitting devices with double electron injection layers

Inverted top-emitting organic light-emitting devices (TEOLEDs) have great potential in flat-panel displays and lighting, yet poor electron injection is a key issue limiting its use in active-matrix OLED. Here, a high-performance green phosphorescent inverted TEOLEDs with ZnO and ZnS double electron injection layers (EILs) were demonstrated. The double EILs which provide a work function gradient can greatly enhance the electron-injection efficiency. For the green phosphorescent TEOLED device based on this double EILs, a high current efficiency of 33.1 cd A(-1) is achieved with low turn-on voltage of 4.0 V. Results indicate that a novel pathway of electron transport to accelerate electron injection is created by applying this double EILs.