Abstract: Polymer doped organic light-emitting diodes (OLEDs) with the structure of indium-tin oxide (ITO)/poly(N-vinylcarbazole) (PVK):(pbi)2Ir(acac)/2,9-dimethyl-4,7-diphenyl-1,10-phenan throline (BCP)/Mg:Ag were fabricated. The light-emitting layer was processed by doping noble metal iridiumcomplex (pbi)2Ir(acac) into a PVKmatrix with the concentrations of 4%and 5%(w), using spin coating method. Through characterizing the UV-Vis absorption spectrum, photoluminescence (PL) spectrum of the (pbi)2Ir(acac) and the electroluminescence (EL) properties of the devices, the main energy transfer mechanisms from phosphorescent material (pbi)2Ir(acac) to PVK were discussed. The device performance was investigated at different current densities and doping concentrations. The results showed that the devices with above two different doping concentrations have the maximum brightness of 11210 and 9174 cd·m-2 and maximum luminance efficiency of 1.53 and 1.31 lm·W-1, respectively. The EL spectrum and the Commissions Internationale de 1’Eclairage (CIE) coordinates were independent on the variation of bias voltage and the doping concentration, indicating a stable color purity.

Key words: Organic light-emitting diode, Phosphorescence, Iridiumcomplex, Polymer doped, Energy transfer, Direct charge trapping