Precise Functionalization of a Multiple‐Resonance Framework: Constructing Narrowband Organic Electroluminescent Materials with External Quantum Efficiency over 40%

Abstract It is of important strategic significance to develop high‐efficiency narrowband organic electroluminescent materials that can be employed to fabricate ultrahigh‐definition displays with wide color gamut. This topic implies a great challenge to molecular design and synthesis, especially for the development of universality, diversity, scalability, and robustness of molecular architectonics. In this work, a synthetic methodology is demonstrated for functionalizing brominated BN‐containing multiple‐resonance (MR) frameworks with multifarious functional groups, such as donors, acceptors, and moieties without obvious push–pull electron properties. The m‐DPAcP–BNCz‐based organic light‐emitting diode (OLED) exhibits green emission with a full‐width at half‐maximum (FWHM) of 28 nm and a maximum external quantum efficiency (EQE) of 40.6%. The outstanding performance of m‐DPAcP–BNCz is attributed to the perfect integration of the inherent advantages of the MR framework and the donor–acceptor configuration, which can not only achieve bathochromic shift and narrowband emission, but also obtain high photoluminescence (PL) quantum yield (Φ_PL) and horizontal emitting dipole orientation ratio (Θ_//). This straightforward and efficient approach provides insightful guidance for the construction and enrichment of more high‐efficiency narrowband emitters.