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 10 mA/cm2 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.