High triplet energy Zn complexes as host materials for green and blue phosphorescent organic light-emitting diodes

•Zn based high triplet energy host materials for phosphorescent organic light-emitting diodes.•High quantum efficiency of 23.5% in green phosphorescent organic light-emitting diodes.•Oxazole and imidazole based ligands for high triplet energy.

Two Zn complexes, bis(2-(oxazol-2-yl)phenolate) zinc (ZnOx2) and bis(2-(1-methyl-1H-imidazol-2-yl)phenolate) zinc (ZnIm2), were synthesized as high triplet energy host materials for green and blue phosphorescent organic light-emitting diodes. High triplet energies of 2.71 eV and 2.84 eV were obtained for ZnOx2 and ZnIm2, respectively. Green and blue phosphorescent devices were fabricated using the ZnOx2 and ZnIm2 host materials and high quantum efficiencies of 23.5% and 20.1% were achieved in green and blue devices, respectively.