ScholarWorks@성균관대학교

초록

The horizontal emitting-dipole-orientation (EDO) in linear and planar small molecules is a widely recognized phenomenon that is critical to the light-outcoupling efficiency and overall performance of organic light-emitting diodes (OLEDs). To maximize the application potential of this phenomenon, two new thermally activated delayed fluorescence (TADF) emitters are designed and synthesized, 10,13-bis(4-(3,6-di-tert-butyl-9H-carbazol-9-yl)phenyl)dibenzo[a,c]phenazine-11,12-dicarbonitrile (tCz-BP2CN) and 10,13-bis(4-(bis(4-(tert-butyl)phenyl)amino)phenyl)dibenzo[a,c]phenazine-11,12-dicarbonitrile (tDPA-BP2CN), exhibiting approximate to 100% horizontal-EDO ratios (98% and 99% for tCz-BP2CN and tDPA-BP2CN, respectively). This high horizontal-EDO ratio is realized by exploiting a para-directed linkage between donor moieties and a planar dibeno[a,c]phenazine acceptor unit. The employed T-shaped geometry design strategy enhances molecular planarity, realizing near-perfect EDO ratios of approximate to 100% in both emitters. Additionally, the adopted T-shaped geometry induced a hydrogen bonding effect between the donor and acceptor units, thereby enhancing the photoluminescence quantum yield of the tDPA-BP2CN emitter. Overall, OLEDs incorporating tDPA-BP2CN as a TADF emitter exhibit a high external quantum efficiency, 18.5%, with pure-red emission at 657 nm.

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