Achieving Deep‐Blue Through‐Space Charge‐Transfer Emitter by Designing the Donor‐π‐Donor‐σ‐Acceptor Molecular Structure

Abstract In the realm of organic light‐emitting diode (OLED), through‐space charge transfer (TSCT) thermally activated delayed fluorescence (TADF) emitters have demonstrated remarkable achievements. Nevertheless, realizing both deep‐blue emission and high efficiency by the TSCT strategy remains a persistent challenge. Here, the novel donor‐π‐donor‐σ‐acceptor (D‐π‐D‐σ‐A) type deep‐blue TSCT emitter, namely D‐tCz‐BO, is formulated to investigate its performance in OLED. D‐tCz‐BO show a narrow deep‐blue emission and efficient TADF character ( λ PL = 448, FWHM = 54 nm, Φ PL = 82%, and Δ E ST = 0.09 eV). More importantly, the OLED based on D‐tCz‐BO as the emitter showed a maximum external quantum efficiency (EQE max ) of 20.5%, with a Commission Internationale de l'Eclairage (CIE) coordinate of (0.14, 0.12). This represents one of the best deep‐blue TSCT‐TADF emitters to date.