Ultra-Narrowband Blue Multi-Resonance Thermally Activated Delayed Fluorescence Materials.

Ultra-narrowband blue multi-resonance-induced thermally activated delayed fluorescence (MR-TADF) materials (V-DABNA and V-DABNA-F), consisting of three DABNA subunits possessing phenyl or 2,6-difluorophenyl substituents on the peripheral nitrogen atoms are synthesized by one-shot triple borylation. Benefiting from the inductive effect of fluorine atoms, the emission maximum of V-DABNA-F (464 nm) is blueshifted from that of the parent V-DABNA (481 nm), while maintaining a small full width at half maximum (FWHM, 16 nm) and a high rate constant for reverse intersystem crossing (6.5 × 10 s ).

One-Shot Synthesis of Expanded Heterohelicene Exhibiting Narrowband Thermally Activated Delayed Fluorescence.

An expanded heterohelicene consisting of three BN-embedded [4]helicene subunits () has been synthesized by one-shot triple borylation. The key to success is the excessive use of boron tribromide in an autoclave. Based on the multiple resonance effect of three boron and six nitrogen atoms, exhibited a narrowband sky-blue thermally activated delayed fluorescence with a full width at half-maximum of 16 nm.

Multiple Electrophilic C-H Borylation of Arenes Using Boron Triiodide.

Electrophilic C-H borylation of arenes using boron triiodide has been developed. This reaction proceeded smoothly in the absence of additives, and the diiodoboryl group was installed at the most sterically accessible carbon, where the HOMO is localized to a certain extent. Moreover, regioselective multiple borylation of polycyclic aromatic compounds was achieved by using excess boron triiodide.

Multiple Resonance Effect-Induced Sky-Blue Thermally Activated Delayed Fluorescence with a Narrow Emission Band.

Efficient thermally activated delayed fluorescence materials based on the multiple resonance effect were synthesized by nucleophilic substitution and electrophilic C-H borylation, featuring a small energy gap between the singlet and triplet state, high photoluminescence quantum yield, and narrow emission band. Organic light-emitting diodes employing these materials as emitters exhibited sky-blue emission with a high external quantum efficiency of 21.4% and a narrow full width at half-maximum of 33 nm.