High‐Performance Orange–Red Organic Light‐Emitting Diodes with External Quantum Efficiencies Reaching 33.5% based on Carbonyl‐Containing Delayed Fluorescence Molecules

Developing orange to red purely organic luminescent materials having external quantum efficiencies ( η ext s) exceeding 30% is challenging because it generally requires strong intramolecular charge transfer, efficient reverse intersystem crossing (RISC), high photoluminescence quantum yield ( Φ PL ), and large optical outcoupling efficiency ( Φ out ) simultaneously. Herein, by introducing benzoyl to dibenzo[ a , c ]phenazine acceptor, a stronger electron acceptor, dibenzo[ a , c ]phenazin‐11‐yl(phenyl)methanone, is created and employed for constructing orange–red delayed fluorescence molecules with various acridine‐based electron donors. The incorporation of benzoyl leads to red‐shifted photoluminescence with accelerated RISC, reduced delayed lifetimes, and increased Φ PL s, and the adoption of spiro‐structured acridine donors promotes horizontal dipole orientation and thus renders high Φ out s. Consequently, the state‐of‐the‐art orange–red organic light‐emitting diodes are achieved, providing record‐high electroluminescence (EL) efficiencies of 33.5%, 95.3 cd A −1 , and 93.5 lm W ‒1 . By referring the control molecule without benzoyl, it is demonstrated that the presence of benzoyl can exert significant positive effect over improving delayed fluorescence and enhancing EL efficiencies, which can be a feasible design for robust organic luminescent materials.