A Highly Efficient Universal Bipolar Host for Blue, Green, and Red Phosphorescent OLEDs

The bipolar host material BCPO (bis-4-(N-carbazolyl)phenylphosphine oxide) containing a phosphine oxide and two carbazole groups, synthesized in three steps, shows a high triplet energy gap of 3.01 eV. The material can be used as a universal host for blue, green, and red phosphorescent devices, all giving extremely high efficiencies with turn-on voltages within 3 V.