High‐Performance Ultra‐Narrowband Blue Electroluminescence via Intramolecular Noncovalent Interaction‐Enhanced Multiple Resonance Emitters

ABSTRACT The development of high‐performance blue organic light‐emitting diodes (OLEDs) is impeded by the scarcity of molecular scaffolds for ultranarrow multiple‐resonance thermally activated delayed fluorescence (MR‐TADF) emitters and their inherent tendency to suffer from aggregation‐induced broadening and quenching in solid films. To intrinsically address these dual challenges, we report a “soft constraints” molecular design strategy that strategically enhances intramolecular noncovalent interactions. By appending tailored donor (carbazole) or acceptor (triazine) units to the MR‐TADF core, this architecture not only directly suppresses key high‐frequency vibrations (e.g., C─N stretching) to achieve an impressively narrow emission with a full width at half‐maximum (FWHM) of 19 nm in solution, but also effectively inhibits detrimental π…π stacking between the emissive cores. The resulting emitters Cz‑TBN and TRZ‑TBN retain ultranarrow emission (FWHM ≈ 23 nm) and high external quantum efficiencies (up to 40.5%) in OLEDs across a broad doping range (1–10 wt%); the TRZ‑TBN device also reaches a record power efficiency (67.9 lm W −1 ) for blue MR‐OLEDs. This work offers a generalizable strategy for the rational design of high‐performance blue emitters.