Pyridine-containing bipolar host materials for highly efficient blue phosphorescent OLEDs

A unique molecular design strategy of bipolar host materials is demonstrated by introducing both carbazole electron donor with high triplet energy and pyridine electron acceptor with high electron affinity for highly efficient blue phosphorescent OLEDs. A record high efficieny and reduced efficiency roll-off at a high driving current were achieved for FIrpic-based blue phosphorescent OLEDs by using the present bipolar host materials as a result of good confinement of the triplet excitons on the guest molecules in the emissive layer and improved carrier balance injected into the emissive layer. The findings suggest a new route to further improve performance of phosphorescent OLEDs, especially at a high driving current.