Bipolar host materials for green triplet emitter in organic light-emitting diodes

We have developed novel bipolar host materials for high efficiency green phosphorescent OLEDs (PHOLEDs). Phenyl moieties were inserted in a 9,9'-(biphenyl-4,4'-diyl)dicarbazole (CBP) compound to provide much easier electron injection and to increase electron mobility. The efficiency increase and voltage reduction by this modification were observed in green PHOLEDs. At a given constant luminance of 1000 cd/m(2), the power efficiency was enhanced about twenty percent in the general green PHOLED devices.