Nitrogen‐Free Multi‐Resonance Skeletons With Intrinsically Twisted Structures, Fast Spin‐Flipping Rates and Aggregation‐Resistant Characteristics for Efficient Deep‐Blue Narrowband Electroluminescence

ABSTRACT Different from conventional nitrogen‐doped multi‐resonance (MR) polycyclic aromatics with planar structures and aggregation emissions, novel nitrogen‐free MR skeletons based on selenium/chalcogen‐doped polycyclic aromatics with intrinsically twisted structures, fast spin‐flipping rates and aggregation‐resistant characteristics are developed for efficient deep‐blue narrowband emission. Weak intermolecular π ‐stacking and aggregation emission at high doping concentrations are realized for the naked skeletons without decoration owing to their inherent deplanarized geometrical configurations induced by much longer Se─C bonds (1.87−1.91 Å) than B−C bonds (1.52−1.57 Å) in the formed selenaborinane heterocycles. Meanwhile, fast reverse intersystem crossing with rate constants up to 8.6 × 10 6 s −1 are triggered by strong spin‐orbit coupling of selenium, which are more than 100‐fold higher than the nitrogen‐based counterpart. Solution‐processed organic light‐emitting diode employing selenium/oxygen‐doped MR emitter exhibits high‐efficiency deep‐blue narrowband electroluminescence with state‐of‐the‐art external quantum efficiency of 20.4% without need of using sensitizer, paving the way for the development of efficient nitrogen‐free MR emitters beyond nitrogen‐doped polycyclic aromatics.