Over 20% external quantum efficiency in red thermally activated delayed fluorescence organic light-emitting diodes using a reverse intersystem crossing activating host

Highly efficient red thermally activated delayed fluorescence organic light-emitting diodes were developed using a reverse intersystem crossing activating host derived from phenylcarbazole and pyridofuropyridine. An ambipolar type 3-(9-phenyl-9H-carbazol-3-yl)furo[2,3-b:5,4-b′]dipyridine (3PCzPFP) host material was prepared by coupling pyridofuropyridine with 9-phenylcarbazole via the 3-position of the 9-phenylcarbazole. The 3PCzPFP host material was doped with a red-emitting thermally activated delayed fluorescence emitter and reached a high quantum efficiency of 24.3%, which is one of the highest quantum efficiencies of red thermally activated delayed fluorescence devices. The material design, with a high dipole moment facilitating reverse intersystem crossing and ambipolar charge transport character, increased the quantum efficiency of the red thermally activated delayed fluorescence devices.