Very high-efficiency organic light-emitting diodes based on cyclometallated rhenium (I) complex

A phosphorescent (Ph) cyclometallated rhenium (1) (Re-I) complex was synthesized by reacting 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline with pentacarbonylbromorhenium in refluxing toluene solutions. The precipitates were easily sublimed to obtain a pure electrically neutral carbonyl diamine Re-I complex, (2,9-dimethyl-4,7-diphenyl-1, 10-phenanthroline)Re(CO)(3)Br. The Re complex was used as an orange emitting dopant in 4,4'-N,N'-dicarbazole-biphenyl host to fabricate Ph organic light-emitting diodes (PhOLEDs). The maximum electroluminescence (EL) efficiency and luminance of 21.8 cd/A and 8315 cd/cm(2) were harvested, respectively, which were the highest EL results among the PhOLEDs based on Re-I complexes. The improvements of the EL performances could be ascribed to the synergistic effects of together incorporation of two reciprocally repulsive phenyl and methyl groups on the backbone of 1,10-phenanthroline molecule of the ligand. (c) 2008 American Institute of Physics.