Merging Boron and Carbonyl based MR‐TADF Emitter Designs to Achieve High Performance Pure Blue OLEDs**

Multiresonant thermally activated delayed fluorescence (MR-TADF) compounds are attractive as emitters for organic light-emitting diodes (OLEDs) as they can simultaneously harvest both singlet and triplet excitons to produce light in the device and show very narrow emission spectra, which translates to excellent color purity. Here, we report the first example of an MR-TADF emitter (DOBDiKTa) that fuses together fragments from the two major classes of MR-TADF compounds, those containing boron (DOBNA) and those containing carbonyl groups (DiKTa) as acceptor fragments in the MR-TADF skeleton. The resulting molecular design, this compound shows desirable narrowband pure blue emission and efficient TADF character. The co-host OLED with DOBDiKTa as the emitter showed a maximum external quantum efficiency (EQE