Correlation of Molecular Structure with Photophysical Properties and Device Performances of Thermally Activated Delayed Fluorescent Emitters

Thermally activated delayed fluorescent (TADF) emitters having bicarbazole as a donor unit based on a twin emitting core design were developed by substituting the bicarbazole donor with a diphenyltriazine acceptor. Three bicarbazole derived delayed fluorescent emitters linked via 2,3′-, 3,3′-, and 3,4′-positions of carbazole were synthesized and investigated as blue dopants of the TADF devices. A twin emitting core based TADF emitter derived from a 3,3′-bicarbazole donor exhibited a high quantum efficiency of 25.0% in the greenish blue TADF device. A 3,3′-linkage induced red shift of the emission wavelength, a small singlet–triplet energy gap, and a high quantum efficiency were revealed.