Recombination zone in organic light emitting diodes with emitting layer of diphenylanthracene-derivative host

White organic light emitting diode devices based on blue-green emitter DSA-ph (1-4-di-[4-(N,N-di phenyl)amino]styrylbenzene) has been studied by co-doping orange emitter. The recombination zone is confirmed to be a region near the interface of hole transport and emitting layers. Although the emission color changes with increasing applied voltage in the co-doped device, white light with high luminance of 16800 cd/m2 was obtained at low voltage of 3.8 V. The maximum luminance efficiency of 14 cd/A was obtained in non-co-doped device.