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

摘要

A novel device design extending the lifetime of white organic light-emittingdiodes (WOLEDs), comprising a thermally activated delayed fluorescent(TADF) blue emitter and a yellow phosphorescent emitter, is developedusing a triplet exciton manager (TEM), which selectively quenches the tripletexciton of the blue TADF emitter while harvesting the yellow phosphorescentemission. The TEM host is designed to have a lower triplet energy than theblue TADF emitter and a higher triplet energy than the yellow phosphorescentemitter. The singlet excitons of the TEM host are used to harvest only thesinglet excitons of the blue TADF emitter by energy transfer, while the tripletexcitons of the TEM host are utilized to activate the phosphorescent emissionof the yellow emitter. The singlet and triplet excitons of the TEM host arethus selectively used to harness the blue singlet emission and yellow tripletemission, respectively. The triplet excitons of the blue TADF emitter can thusbe excluded from the emission process, which improves the lifetime of theTEM-based WOLEDs by five times while achieving similar external quantumefficiency as that of the conventional WOLED with a common high tripletenergy host activating the triplet excitons of the blue TADF emitter.