Bridged resonance configuration enables high-efficiency and narrow-emission in blue organic light-emitting diodes

Multi-resonance thermally activated delayed fluorescence (MR-TADF) materials hold significant promise for narrowband organic light-emitting diodes (OLEDs), particularly for blue emission required in ultra-high-definition displays. However, the unsatisfactory exciton dynamics limit the electroluminescence efficiency of blue organic light-emitting diodes. Herein, we propose a bridged resonance configuration to modulate triplet excited states, achieving high photoluminescence quantum yields, small singlet–triplet splittings, and enhanced spin–orbit couplings in the proof-of-concept molecules, BNCz-BOCz and BNA-BOCz. Incorporation into devices delivered high external quantum efficiencies (EQEs) of 40.2% and 36.9%, respectively, coupled with narrowband blue (CIEy = 0.21) and deep-blue electroluminescence (CIEy = 0.08), meeting stringent criteria for high-color-purity blue emission. Moreover, the hyperfluorescent devices demonstrated remarkably high EQE, reaching 42.6% for BNCz-BOCz and 40.7% for BNA-BOCz, with suppressed efficiency roll-off. The satisfactory electroluminescent performance validates the bridged resonance configuration as a practical molecular design strategy that addresses the key limitations of existing blue MR-TADF emitters. Unsatisfactory exciton dynamics limits the electroluminescence efficiency of blue organic light-emitting diodes. He et al. proposed a bridged resonance configuration to modulate triplet excited states, achieving an external quantum efficiency of 42.6%.