A class of oxadiazole-functionalized iridium complexes was used as phosphor emitters in poly (vinylearbazole)-hosted devices. Efficient green electrophosphorescences were achieved in the devices with a maximum luminance efficiency of 9.3 cd/A at 10.6 mA/cm(2) and brightness of 3882 cd/m(2) at 92.1 mA/cm(2). More importantly, the iridium complexes-doped devices exhibited a low turn-on voltage of 7.0 V and an applied voltaae of 9.2 V at 500 cd/m(2). The good optoelectronic properties of the complexes were attributed to the enhanced electron-injection and transport properties resulting from the effect of oxadiazole ligands in the complexes. (c) 2007 Elsevier B.V. All rights reserved.