Asymmetric Design of Bipolar Host Materials with Novel 1,2,4-Oxadiazole Unit in Blue Phosphorescent Device

The intrinsic asymmetry of 1,2,4-oxadiazole was utilized to synthesize three isomers, DCzmOXD-1, DCzmOXD-2, and mCzmOXD, and high triplet energies over 2.80 eV made them good candidates for host materials in blue OLEDs. The best efficiencies of 23.0 cd A(-1)/20.5 lm W(1-)/11.2% in CE/PE/EQE were achieved by DCzmOXD-1 with derivation at the β-carbon position of 1,2,4-oxadiazole.