Fluorene-fused Dimeric Carbonyl/amine Multiresonant Thermally Activated Delayed Fluorescence Emitter for Efficient Green OLEDs

Multiresonant thermally activated delayed fluorescence (MR-TADF) materials possessing narrow emission spectra have attracted significant attention as emitters for use in high color purity organic light-emitting diodes (OLEDs). Here we report a fluorene-fused dimeric carbonyl/amine MR TADF emitter DDiKTa-F that is designed to show narrower and brighter emission than the previously reported compound DDiKTa. By locking the conformation of the molecule using a fluorene bridge, a narrower, brighter (PL = 78%), and red-shifted emission at 494 nm (FWHM of 49 nm) was obtained. The OLEDs with DDiKTa-F emitted at 493 nm and showed an EQEmax of 15.3%. Despite a slightly lower efficiency compared to the previously reported device with DDiKTa, the device exhibited a lower efficiency roll-off of 35% at 100 cd m-2.