Synthesis and their device performance of solution processable host materials based on carbazole derivatives

New carbazole based soluble high triplet-energy host materials, 9-(4-(bis(9-ethyl-9H-carbazol-3-yl)methyl)phenyl)-9H-carbazole and (9-(4-(bis(9-ethyl-9H-carbazol-3-yl)methyl)phenyl)-9H-carbazole-3,6-diyl)bis(diphenylphosphine oxide), were synthesized and device performances of solution processed blue PHOLEDs were investigated. These host materials showed a high triplet energy (∼2.94 eV), excellent film formation ability and thermal stability. The maximum external quantum efficiency of blue PHOLEDs reached as high as 12.1% with a blue color coordinate of (0.14, 0.19).