3D interlocking triggers intramolecular interactions to achieve an efficient deep‐blue multiple resonance thermal activation delayed fluorescence material

Multi‐resonance thermally activated delayed fluorescence (MR‐TADF) emitters have shown promise for achieving full‐color emission with a high efficiency and a narrow band. However, the development of MR‐TADF materials with both high efficiency and deep‐blue emission for organic light‐emitting diode (OLED) remains a significant challenge. Herein, a B/N‐based MR core and a indolocarbazole group are interlocked in 3D mode to induce intramolecular interaction between both, culminating in the development of the target emitter, DPABN‐ICz. Notably, DPABN‐ICz demonstrates a remarkable deep‐blue emission, peaking at 445 nm, with a small full width at half maximum (FWHM) of 19 nm and a Commission Internationale de L'Eclairage (CIE) y coordinate of 0.06. Interestingly, DPABN‐ICz exhibits an enhanced oscillator strength of 0.2975, resulting in an impressive photoluminescence quantum yield of 94%. Furthermore, the sensitized OLED achieves a high maximum external quantum efficiency of 31.4%, and a narrow electroluminescence with a small FWHM of 27 nm and the CIE coordinates of (0.153, 0.055), closely aligning with the BT.2020 deep‐blue emission standard.