A versatile efficient one-step approach for carbazole-pyridine hybrid molecules: Highly efficient host materials for blue phosphorescent OLEDs

By using various fluoro-substituted pyridines and carbazole as starting materials, we have synthesized a series of carbazole-pyridine hybrid compounds through an efficient catalyst free C-N coupling reaction with high yields of 85-95%. The bi-, tri- and tetra-carbazole substituted pyridine derivatives exhibit increased thermal stabilities and comparatively high triplet energy levels of ∼3.0 eV. By using them as host materials for blue phosphorescent OLEDs, maximum current efficiencies are achieved ranging from 32-42 cd A^-1.