Design of High‐Efficiency and Long‐Lifetime White Organic Light‐Emitting Diodes by Selective Management of Singlet and Triplet Excitons Using a Triplet Exciton Manager

Abstract A novel device design extending the lifetime of white organic light‐emitting diodes (WOLEDs), comprising a thermally activated delayed fluorescent (TADF) blue emitter and a yellow phosphorescent emitter, is developed using a triplet exciton manager (TEM), which selectively quenches the triplet exciton of the blue TADF emitter while harvesting the yellow phosphorescent emission. The TEM host is designed to have a lower triplet energy than the blue TADF emitter and a higher triplet energy than the yellow phosphorescent emitter. The singlet excitons of the TEM host are used to harvest only the singlet excitons of the blue TADF emitter by energy transfer, while the triplet excitons of the TEM host are utilized to activate the phosphorescent emission of the yellow emitter. The singlet and triplet excitons of the TEM host are thus selectively used to harness the blue singlet emission and yellow triplet emission, respectively. The triplet excitons of the blue TADF emitter can thus be excluded from the emission process, which improves the lifetime of the TEM‐based WOLEDs by five times while achieving similar external quantum efficiency as that of the conventional WOLED with a common high triplet energy host activating the triplet excitons of the blue TADF emitter.