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.
Chen et al. (Mon,) studied this question.