Phosphine Oxide Type Bipolar Host Material for High Quantum Efficiency in Thermally Activated Delayed Fluorescent Device

Highly efficient thermally activated delayed fluorescence devices were developed using a bipolar host material, 2,7-bis(diphenylphosphoryl)-9-phenyl-9H-carbazole (PPO27), derived from carbazole and diphenylphosphine oxide. The PPO27 host was effective for good charge balance and energy transfer from the PPO27 host to thermally activated delayed fluorescence dopant. The PPO27 device doped with (4s,6s)-2,4,5,6-tetra(9H-carbazol-9-yl)isophthalonitrile dopant could realize a high quantum efficiency of 24.2%.