A carbazole-functionalized Ir complex used in efficient single-layer electrophosphorescent devices

The fabrication of electroluminescent devices that combine high device performance with simple device configuration remains an attractive challenge for their low costs and simple fabrication process. In this paper, a novel red phosphorescent iridium complex containing a carbazole-functionalized beta-diketonate ligand, bis(1-phenylisoquinolinato-C2,N) iridium 1-(carbazol-9-yl)-5,5-dimethylhexane-2,4-diketonate (Ir(piq)(2)(CBDK)), is designed, synthesized, and characterized. The electrophosphorescence of Ir(piq)(2) (CBDK) as an emitter in organic light-emitting diodes was examined and compared with that of Ir(piq)(2) (acac) (acac = acetylacetonate) without carbazolyl group. A series of single-layer devices containing different concentration gradients of Ir(piq)(2)(CBDK) as an emitting and hole-transporting material and 1,3,5-tris(N-phenylbenzimidazole-2-yl)benzene as an electron-transporting material were constructed. A maximum current efficiency of 9.9 cd A(-1) and power efficiency of 7.8 lm W-1 were obtained, which is one of the best performances obtained for a single-layer device containing one material as a host. (C) 2012 Elsevier Ltd. All rights reserved.