Electroluminescence of an iridium complex phosphorescent material doped polymeric system

Abstract

With a novel iridium complex (pbi)2Ir(acac) doped into carbazole copolymer, polymer doped electrophosphorescent organic light-emitting diodes with the structure of indium-tin oxide(ITO)/poly(N-vinylcarbazole) (PVK):(pbi)2Ir(acac) (x)/2,9-dimethyl-4,7-diphenyl-1,10-phenan throline (BCP) (20nm)/8-Hydroxyquinoline aluminum(Alq3) (10nm)/Mg:Ag were fabricated. The photoluminescent (PL) and electroluminescent (EL) characteristics of the polymer doped system were investigated at the low doping concentrations of 0.1% and 0.5%, respectively. The results demonstrate that the luminescent spectra with different intensities of PVK and (pbi)2Ir (acac) co-existed in the PL and EL spectra of blend system, which was ascribed to an incomplete energy transfer process and direct charge trapping in the electroluminescence process. The 0.1% (pbi)2Ir(acac) doped device achieved a white light emission with the commissions internationale de 1'eclairage (CIE) coordinates of (0.32, 0.38) when the bias voltage was 19V; the 0.5% (pbi)2Ir(acac) doped device had a maximum luminance of 11827 cd·m-2 and a maximum luminance efficiency of 4.13 cd·A-1 corresponding to a bias of 20.6V and 13.4V, respectively.