Despite the success of thermally activated delayed fluorescent (TADF) materials in steering the next generation of organic light-emitting diodes (OLEDs), effective near infrared (NIR) TADF emitters are still very rare. Here, we present a simple and extremely high electron-deficient compound, 5,6dicyano[2,1,3]benzothiadiazole (CNBz), as a strong electronaccepting unit to develop a sufficiently strong donor-acceptor (DÀ A) interaction for NIR emission. End-capping with the electron-donating triphenylamine (TPA) unit created an effective DÀ AÀ D type system, giving rise to an efficient NIR TADF emissive molecule (λ em = 750 nm) with a very small ΔE ST of 0.06 eV. The electroluminescent device using this NIR TADF emitter exhibited an excellent performance with a high maximum radiance of 10020 mW Sr À 1 m À 2 , a maximum EQE of 6.57% and a peak wavelength of 712 nm.
Two D–A–D type emitters exhibited superior simple hole-transporting free solution-processed OLEDs with maximum EQE of 1.52%, low efficiency roll-off and maximum radiance of 4463 mW Sr−1 m−2, which is one the best solution-processed NIR-OLEDs.
The hybridized local and charge-transfer (HLCT) excited state is a successful approach to accomplish both high external and internal quantum efficiency. To attain deep blue emissive HLCT emitters, two cyanophenyl...
A series of excited‐state intramolecular proton transfer (ESIPT)–aggregate‐induced emission (AIE) solid‐state fluorophores (TTHPI, PTHPI, and ATHPI) are reported as self‐absorption‐free emitters for electroluminescent (EL) devices. The molecules contain 2‐(2‐hydroxyphenyl)‐1,4,5‐triphenylimidazole as an ESIPT core being double functionalized with AIE‐active luminogen of tetraphenylethene and hole‐transporting moiety (triphenylamine, N‐(4‐phenyl)phenoxazine, or N‐(4‐phenyl)‐9,9‐dimethylacridine) to improve their solid‐state emission due to the AIE effect and hole‐transporting capability. The ESIPT, AIE, and photophysical properties are theoretically and experimentally studied. All molecules demonstrate ESIPT and AIE characters with intense sky‐blue/green color emissions from a pure keto‐form emission in the solid‐state and photoluminescence quantum yields of 41–74%. These ESIPT–AIE fluorophores exhibit high thermal and electrochemical stabilities with decent hole mobilities and are successfully utilized as emitters in organic light‐emitting diodes (OLEDs). All devices show pure keto‐form EL emissions with moderate‐to‐good EL performances. Particularly, the TTHPI‐based device achieves excellent EL performance with a maximum external quantum efficiency (EQEmax) of 5.21%, a maximum current efficiency (CEmax) of 11.17 cd A−1, and a slight efficiency roll‐off.
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