Thermally Activated Delayed Fluorescence Materials Featuring Multipathway Charge Transfer for High-Efficiency...

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 (D₁-D₂-A) molecular configuration in which C₁-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 D₁ and D₂ 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.