Low resistance and high work-function WO3/Ag/MoO2 multilayer as transparent anode for bright organic light-emitting diodes

The authors report efficient organic light-emitting diodes (OLEDs) using a high conductive transparent WAM multilayer as anode electrode [WAM=WO3 (30nm)/Ag (10 nm)/MoO2 (5 nm)], which was prepared by thermal evaporation under room temperature condition to form the smooth morphology on anode surface, leading to reduce the injection barrier between metal/organic interface. The WAM anode shows a low sheet resistance of 8.27 Ω/sq, suitable injection workfunction of ~5.68 e V, and high optical transmittance of ~80% at range of visible light from 400 to 550 nm. In addition, a hole only WAM-device by atomic-force microscopy and electrical characterizations has demonstrates that the efficient hole injection property is existing at WAM/NPB interface as compared with the standard transparent conductive oxide of indium tin oxide. From the device characterization, the device performance of green fluorescent OLED based on WAM anode exhibiting a high brightness of 150 000 cd/m² and current efficiency of 20 cd/A at driving voltage of 8 V has been achieved.