Constructing organic near‐infrared (NIR) luminescent materials to confront the formidable barrier of “energy gap law” remains challenging. Herein, two NIR thermally activated delayed fluorescence (TADF) molecules named T‐β‐IQD and TIQD were developed by connecting N,N‐diphenylnaphthalen‐2‐amine and triphenylamine with a novel electron withdrawing unit 6‐(4‐(tert‐butyl)phenyl)‐6H‐indolo[2,3‐b]quinoxaline‐2,3‐dicarbonitrile. It is confirmed NIR‐TADF emitters concurrent with aggregation‐induced emission effect, J‐aggregate with intra‐ and intermolecular CN⋅⋅⋅H−C and C−H⋅⋅⋅π interactions, and large center‐to‐center distance in solid states can boost the emissive efficiencies both in thin films and non‐doped organic light‐emitting diodes (OLEDs). Consequently, the T‐β‐IQD‐based non‐doped NIR‐OLED achieved the maximum external quantum efficiency (EQEmax) of 9.44 % with emission peak at 711 nm, which is one of the highest efficiencies reported to date for non‐doped NIR‐OLEDs.
Modulating the emission wavelength in the range of ultraviolet to deep‐blue with high color purity remains elusive. Herein, a versatile strategy is proposed from the perspective of rationally regulating nonbonding/π‐bonding character of frontier molecular orbitals to finely modulate emission colors while retaining superior color purity. By modifying the fused modes of indolo[3,2,1‐jk]carbazole (ICz) units, the proof‐of‐the‐concept emitters emphasize adjustable hybridization of nonbonding and π‐bonding characteristics, achieving a wide‐range color tuning range from ultraviolet (380 nm) to deep‐blue (428 nm) and small full‐width at half‐maximum (FWHM) of 8–33 nm (63–222 meV). Organic light‐emitting diodes based on the new emitter exhibit electroluminescence emission at 430 nm, a small FWHM of 44 nm (253 meV), maximum external quantum efficiency of 10.9%, and CIE color coordinates of (0.16, 0.05). The CIE coordinates are close to the National Television System Committee (NTSC) standard blue of (0.15, 0.06).
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