Carbazolyldibenzofuran-type high-triplet-energy bipolar host material for blue phosphorescent organic light-emitting diodes

A high-triplet-energy material, 9′-(4,4′-(phenylphosphoryl)bis(dibenzo[b,d]furan-6,2-diyl))bis(9H-carbazole) (44DFCzPO), was synthesized as a bipolar host material for blue phosphorescent organic light-emitting diodes (PHOLEDs). 44DFCzPO was synthesized by the selective lithiation of the 4-position of a carbazole-modified dibenzofuran, followed by phosphorylation. 44DFCzPO showed a high triplet energy of 2.91 eV for energy transfer to a blue phosphorescent dopant, and bipolar charge transport properties for balanced hole and electron density in the emitting layer. A high quantum efficiency of 16.7% at a low doping concentration of 3% was obtained using 44DFCzPO as the host in blue PHOLEDs.