Green Phosphorescent Organic Light-Emitting Diode Based on Interlayer Emitting Layer Blend of Hole- and Electron-Transporting Materials as a Co-Host of the Three Emitting Layers

Highly efficient green phosphorescent organic light-emitting diodes (PHOLEDs) are achieved by using a three emitting layers structure in which the interlayer composes a blend of a hole- and an electron-transporting materials as the co-host. Both the efficiency and operational lifetime of the devices are improved with such a three emitting layers structure. The optimized device shows a maximum current efficiency and luminance of 65.8 cd/A and 127435 cd/m(2), respectively, which are nearly two folds over the conventional structure device. The three emitting layers structure improves the charge carriers injection and transport balance and confinement in the emitting layers, which lead to increasing charge carriers recombination probability and decreasing exciton annihilation by the hole transporting and electron transporting materials. Such factors are critical to improve the efficiency and operational lifetime of the green PHOLEDs. (C) 2014 The Electrochemical Society.