Merging Boron and Carbonyl based MR-TADF Emitter Designs to Achieve High Performance Deep Blue OLEDs

Multiresonant thermally activated delayed fluorescence (MR-TADF) compounds are attractive as emitters for organic light-emitting diodes (OLEDs) as they simultaneously can harvest both singlet and triplet excitons to produce light and show very narrowband emission, which translates to excellent colour purity. Here, we report the first example of a MR-TADF emitter (DOBDiKTa) that fuses together fragments from the two major classes of MR-TADF compounds, those containing boron and those containing carbonyl groups as acceptor fragments in the polycyclic aromatic hydrocarbon skeleton. Using this molecular design, this compound shows desirable narrowband deep blue emission and efficient TADF character. The OLED with DOBDiKTa as the emitter and mCP:PPT (1:1) as the co-host exhibits an EQEmax of 17.4%, an efficiency roll-off of 32% at 100 cd m-2, and CIE coordinates of (0.14, 0.12). Compared to DOBNA and DiTKa, DOBDiKTa shows higher device efficiency with reduced efficiency roll-off while maintaining a narrow pure blue electroluminescence, which demonstrates the promise of the proposed molecular design.