Thermally activated delayed fluorescence (TADF) materials, which enable the full harvesting of singlet and triplet excited states for light emission, are expected as the third-generation emitters for organic light-emitting diodes (OLEDs), superseding the conventional fluorescence and phosphorescence materials. High photoluminescence quantum yield (Φ PL ), narrow-band emission (or high color purity), and short delayed fluorescence lifetime are all strongly desired for practical applications. However, to date, no rational design strategy of TADF emitters is established to fulfill these requirements.Here, an epoch-making design strategy is proposed for producing high-performance TADF emitters that concurrently exhibiting high Φ PL values close to 100%, narrow emission bandwidths, and short emission lifetimes of ≈1 µs, with a fast reverse intersystem crossing rate of over 10 6 s −1 . A new family of TADF emitters based on dibenzoheteraborins is introduced, which enable both doped and non-doped TADF-OLEDs to achieve markedly high external electroluminescence quantum efficiencies, exceeding 20%, and negligible efficiency roll-offs at a practical high luminance. Systematic photophysical and theoretical investigations and device evaluations for these dibenzoheteraborin-based TADF emitters are reported here.

BBC news: Two boron atoms have been incorporated into a carbon nanosheet by a bottom‐up synthesis to give a “B‐doped nanographene” (see picture) with a defined structure. The experimental and theoretical analyses revealed the important role of the two boron atoms in producing its characteristic properties, such as broad absorption bands covering the visible region and reversible redox processes.

We disclose a new planarized triarylborane in which the tri-coordinated boron atom is embedded in a fully fused polycyclic π-conjugated skeleton. The compound shows high stability toward oxygen, water, and silica gel, despite the absence of steric protection around the B atom. Reflecting the electron-donating character of the π-skeleton and the electron-accepting character of the B atom, this compound shows broad absorption bands that cover the entire visible region and a fluorescence in the visible/near-IR region. In addition, this compound shows dramatic property changes upon formation of a tetra-coordinated borate, such as thermochromic behavior in the presence of pyridine.

The synthesis of a planarized trinaphthylborane with partially fused structure is presented. This compound shows not only high chemical and thermal stability but also sufficient Lewis acidity to form Lewis adducts with pyridine derivatives in solution. The B-N Lewis adducts exhibit unprecedented photodissociation behavior in the excited state, reminiscent of the photogeneration of carbenium ions from triarylmethane leuco dyes. Consequently, these B-N Lewis adducts exhibit dual fluorescence emission arising from the initial tetracoordinate B-N adducts and the photodissociated tricoordinate boranes.

Organic luminescent materials that exhibit thermally activated delayed fluorescence (TADF) can harvest both singlet and triplet excitons for light emission, leading to high electroluminescence (EL) quantum efficiencies in organic light‐emitting diodes (OLEDs). However, efficient red TADF materials are still very rare because of their restricted molecular design based on the energy gap law. To address this issue, elaborate π‐conjugated donor–acceptor (D–A) systems that can simultaneously achieve a large fluorescence radiative rate and small singlet–triplet energy splitting should be strategically designed. In this study, to produce high‐efficiency pure‐red TADF materials, a remarkably strong π‐accepting dicyanodibenzo[a,c]phenazine (CNBPz) unit has been introduced in a D–π–A molecular framework, and combined with a phenylene‐linked p‐ditolylamine or 9,9‐dimethylacridan moiety. The steady‐state and time‐resolved photophysical measurements revealed intense genuine red TADF emissions of these CNBPz‐based molecules in both solution and doped thin films. The OLEDs incorporating the CNBPz‐based TADF emitters achieve the desired high‐efficiency pure‐red EL, centered at 670 nm with color coordinates of (0.66, 0.34), accompanied by a high maximum external EL quantum efficiency of 15.0%. Therefore, it is concluded that CNBPz, with its expanded π‐conjugation and strong electron‐accepting characteristics, is a particularly useful building unit to design long‐wavelength TADF materials that can overcome the intrinsic energy gap law obstacle.

exo-Methylene lactone group-containing compounds, such as (−)-xanthatin, are present in a large variety of biologically active natural products, including extracts of Xanthium strumarium (Cocklebur). These substances are reported to possess diverse functional activities, exhibiting anti-inflammatory, antimalarial, and anticancer potential. In this study, we synthesized six structurally related xanthanolides containing exo-methylene lactone moieties, including (−)-xanthatin and (+)-8-epi-xanthatin, and examined the effects of these chemically defined substances on the highly aggressive and farnesyltransferase inhibitor (FTI)-resistant MDA-MB-231 cancer cell line. The results obtained demonstrate that (−)-xanthatin was a highly effective inhibitor of MDA-MB-231 cell growth, inducing caspase-independent cell death, and that these effects were independent of FTase inhibition. Further, our results show that among the GADD45 isoforms, GADD45γ was selectively induced by (−)-xanthatin and that GADD45γ-primed JNK and p38 signaling pathways are, at least in part, involved in mediating the growth inhibition and potential anticancer activities of this agent. Given that GADD45γ is becoming increasingly recognized for its tumor suppressor function, the results presented here suggest the novel possibility that (−)-xanthatin may have therapeutic value as a selective inducer of GADD45γ in human cancer cells, in particular in FTI-resistant aggressive breast cancers.

Blue thermally activated delayed fluorescence emitters incorporating phenazasiline and phenazagermine as donor units are developed, and their structural, photophysical, and electroluminescent properties are systematically investigated.

The impact of boron doping on the nature of nanographene was investigated at the molecular level in terms of chemical adsorption with various Lewis bases, spin multiplicity of the two electron-reduced species, and performance as a battery electrode.