High‐Performance Red OLEDs Enabled by an Organoboron‐Nitrogen‐Carbonyl‐Hybridized Multiresonant Emitter

Abstract Organoboron‐nitrogen‐carbonyl‐hybridized (h‐BNCO) frameworks are emerging templates for developing high‐performance multiresonant (MR) emitters, but their potentials have not been fully explored. In this study, a novel red MR emitter, namely, h‐BNCO‐3, is developed by decorating two diphenylamine moieties onto a h‐BNCO MR skeleton (h‐BNCO‐2). Compared with the green backbone, h‐BNCO‐3 achieves a substantial emission redshift of 76 nm while retaining a narrow full width at half maximum (FWHM) of 45 nm (0.16 eV) in toluene. Moreover, the common advantages of integrating a carbonyl group in B/N‐based systems, e.g., significant nπ^* contribution in the triplet manifolds, are obvious in h‐BNCO‐3. Thus, h‐BNCO‐3 obtained a fast reverse intersystem crossing rate (k_RISC) of over 10⁵ s⁻¹. The optimized non‐sensitized organic light‐emitting diode (OLED) based on h‐BNCO‐3 achieved red emission with an external quantum efficiency (EQE) of 26.4%. Moreover, by further employing a phosphor as a sensitizer, the h‐BNCO‐3‐based OLED can reach an impressive EQE of 38.0%, which is among the best results of red MR‐OLEDs. This work demonstrates the effectiveness of integrating carbonyl into organoboron‐nitrogen‐based frameworks with peripheral decorations for enhancing k_RISC, offering new insights for developing high‐performance MR emitters based on h‐BNCO systems.