P‐178: Synthesis of Reverse Intersystem Crossing Facilitating Host Material for High Efficiency in Red Thermally Activated Delayed Fluorescent Organic Light‐emitting Diodes

In this study, we introduced a reverse intersystem crossing activating host material to obtain high efficiency in red thermally activated delayed fluorescent organic light‐emitting diodes. The host material was composed of phenylcarbazole and pyridofuropyridine moieties. The 3‐(9‐phenyl‐9H‐carbazol‐3‐yl)furo[2,3‐b:5,4‐b′]dipyridine (3PCz‐PFP) host material was synthesized by introducing pyridofuropyridine at 3‐ position of the 9‐phenylcarbazole. We were able to obtain a high external quantum efficiency of 24.0% by doping red‐emitting thermally activated delayed emitter in 3PCz‐PFP host material. This efficiency is one of the highest efficiencies in red thermally activated delayed fluorescent devices. The high quantum efficiency of the red thermally activated delayed fluorescent devices was achieved due to improved reverse intersystem crossing rate and ambipolar charge transport character of the host material.