Thermally Activated Delayed Fluorescence Materials Featuring Multipathway Charge Transfer for High‐Efficiency BT.2020‐Compliant Deep‐Blue OLEDs

Abstract BT.2020‐compliant deep‐blue emitters for organic light‐emitting diodes (OLEDs) are in high demand to achieve a wide color gamut for ultrahigh‐definition displays. Herein, we report deep‐blue thermally activated delayed fluorescent emitters featuring a unique donor1‐donor2‐acceptor (D 1 ‐D 2 ‐A) molecular configuration in which C 1 ‐N linked carbazole derivatives serve as dual‐function donors and an oxygen‐bridged triarylboron unit acts as the acceptor. The new design strategy focuses on constructing excited states with multipathway charge transfer characteristics—including multiresonance, through‐bond, and through‐space charge transfer—by precisely tuning the relative electron‐donating strengths of the D 1 and D 2 units. Experimental and theoretical studies reveal that the optimized emitter, BO‐BTC, achieves a well‐balanced trade‐off among emission efficiency, color purity, singlet–triplet energy gap, and horizontal dipole orientation ratio. Consequently, OLEDs using BO‐BTC as the terminal emitter or as the sensitizer for ν ‐DABNA achieve high‐efficiency deep‐blue electroluminescence, with external quantum efficiencies of up to 24.7% and 37.9%, Commission Internationale de l’Éclairage‐y values of 0.038 and 0.106, respectively.