High efficiency deep blue phosphorescent organic light-emitting diodes using a double emissive layer structure

High efficiency deep blue phosphorescent organic light-emitting diodes (PHOLEDs) have been developed with a double emissive layer structure (D-EML). Using bis(4',6'-difluorophenylpyridinato)tetrakis(1-pyrazolyl)borate (FIr6) as an electro-phosphorescent dopant, we achieved a maximum external quantum efficiency of 14.8% in the deep blue PHOLEDs with D-EMLs, which is 50% higher value than that of 9.76% with single emissive layer structure (S-EML). Moreover, the external quantum efficiency at high current density region of 10mA/cm(2) was maintained up to 11.3% in this D-EML device. We attributed this enhancement to the expansion of carrier recombination region and the effective confinement of exciton within the emissive layer. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.