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A novel three-dimensional tetracoordinated organoboron acceptor bearing C^N^C chelate was developed by the direct borylation of pyridine derivatives. Donor-acceptor type emitter based on this novel organoboron acceptor exhibited good stability, high photoluminescence quantum yield (PLQY) and thermally activated delayed fluorescence (TADF) character. By selecting different donors with different electron donating abilities, two distinct electroluminescence devices with white and green emission achieved maximum external quantum efficiency of over 10%. • A novel tetracoordinated organoboron acceptor bearing C^N^C chelate. • Donor-acceptor type emitter based on this acceptor exhibited thermally activated delayed fluorescence. • White and green EL devices with maximum external quantum efficiency of over 10%. [ABSTRACT FROM AUTHOR]

Organic light‐emitting diodes (OLEDs) with simple nondoped device structure are extremely attractive for real applications since excitons can be utilized without considering the possible charge trapping and morphology issues in the host–dopant systems. Emitters with suppressed concentration annihilation capability are essential for nondoped devices. Herein, two thermally activated delayed fluorescence (TADF) emitters based on a novel 3D electron donor, namely, TDMAC, are constructed. The TDMAC donor consists of a conventional donor with fused triptycene scaffold. Benefitting from the unique rigid and bulky triptycene moiety, these TADF emitters exhibit excellent thermal, morphological, and photophysical properties. Consequently, highly efficient OLEDs with external quantum efficiencies up to 24.2% and 23% are realized for doped and nondoped devices, respectively. [ABSTRACT FROM AUTHOR]

Organic light‐emitting diodes (OLEDs) with simple nondoped device structure are extremely attractive for real applications since excitons can be utilized without considering the possible charge trapping and morphology issues in the host–dopant systems. Emitters with suppressed concentration annihilation capability are essential for nondoped devices. Herein, two thermally activated delayed fluorescence (TADF) emitters based on a novel 3D electron donor, namely, TDMAC, are constructed. The TDMAC donor consists of a conventional donor with fused triptycene scaffold. Benefitting from the unique rigid and bulky triptycene moiety, these TADF emitters exhibit excellent thermal, morphological, and photophysical properties. Consequently, highly efficient OLEDs with external quantum efficiencies up to 24.2% and 23% are realized for doped and nondoped devices, respectively. [ABSTRACT FROM AUTHOR]

• A new building block with versatile functionality for constructing TADF emitters. • Facile molecular engineering to facilitate RISC process and boost Φ PL. • TADF OLEDs with EQE up to 20.4% and small efficiency roll-off. This contribution describes sulfoximine (SFI) derivatives as a novel type of acceptor for efficient thermally activated delayed fluorescence (TADF) emitters. SFI presents a unique advantage by facile introduction of versatile functionalities on its secondary amine, which allows delicate manipulation of TADF properties. In a proof of principle study, three green/yellowish green TADF emitters, namely DMAC-SFIP , DMAC-SFIC and DMAC-SFIS were developed with different electron-withdrawing N -substituents based on simple donor–acceptor (D-A) typed structure. A look into the molecular conformations indicates the existence of different types of weak intramolecular interactions to suppress nonradiative decay. More importantly, effective mixing between charge transfer (CT) and locally excited (LE) triplet states is observed for DMAC-SFIP , DMAC-SFIC due to suitable electron-deficiency in the SFI segment, resulting in acceleration of the reverse intersystem crossing (RISC) rate. Consequently, these new TADF emitters render excellent organic light-emitting diode (OLED) performances with external quantum efficiencies (EQEs) up to 20.4% and small efficiency roll-off. [ABSTRACT FROM AUTHOR]