No abstract

Developing organic luminophores with unique capability of strong narrowband emission is both crucial and challenging for the further advancement of organic light‐emitting diodes (OLEDs). Herein, a nanographitic fused‐nonacyclic π‐system (BSBS‐N1), which was strategically embedded with multiple boron, nitrogen, and sulfur atoms, was developed as a new multi‐resonance thermally activated delayed fluorescence (MR‐TADF) emitter. Narrowband sky‐blue emission with a peak at 478 nm, full width at half maximum of 24 nm, and photoluminescence quantum yield of 89 % was obtained with BSBS‐N1. Additionally, the spin‐orbit coupling was enhanced by incorporating two sulfur atoms, thereby facilitating the spin‐flipping process between the excited triplet and singlet states. OLEDs based on BSBS‐N1 as a sky‐blue MR‐TADF emitter achieved a high maximum external electroluminescence quantum efficiency of 21.0 %, with improved efficiency roll‐off.

Nanoclusters (NCs) of several to hundreds of atoms in size are prospective functional units for future nanomaterials originating in their unique, size-specific properties. To explore the field of NC-based materials science, the development of large-scale, size-exclusive synthesis methods is in high demand, as one can see from the successful evolution of fullerene science. We have developed a large-scale synthesis method for main group-based NC compounds by scaling up the clean dry-process with a high-power impulse magnetron sputtering. The 100 mg scale synthesis of binary NCs of M@Si16 (M = Ti and Ta) stabilized by poly­(ethylene glycol) dimethyl ether enables us to characterize their structures by an array of methods, for example, mass spectroscopy, X-ray photoemission spectroscopy, Raman spectroscopy, and 29Si nuclear magnetic resonance. Spectroscopic evidence indicates that the M@Si16 NCs are the metal-encapsulating tetrahedral silicon-cage structure satisfying the 68 electrons, closed-electronic-shell superatom.

Fluorinated [6]- and [9]cycloparaphenylene (CPP) derivatives, 8F-[6]CPP and 12F-[9]CPP, were synthesized based on the previous synthesis of the parent CPPs. While the reductive aromatization conditions used in the final step of the synthesis of the parent CPPs did not work for the fluorinated compounds, the use of PBr and SnCl in acetonitrile successfully accomplished the desired transformation. The structures of F-CPPs were determined by single-crystal X-ray analysis. Photo- and electrochemical analyses and host-guest chemistry revealed the effects of the introduction of fluorine atoms.

As one of the three primary colors, blue is significant for display and lighting applications and the development of blueemitting molecules with high quantum efficiency, and color purity for organic light-emitting diodes (OLEDs) remains a key challenge. Herein, a new series of blue thermally activated delayed fluorescence (TADF) materials featuring π-extended ladderoxaborin and thiaborin acceptors has been developed. Steadystate and time-resolved photophysical measurements revealed the advantages of the ladder-oxaborin emitter, including a tiny singlet− triplet energy splitting of 10 meV, an ideal photoluminescence quantum yield of 100%, and an ultrashort TADF lifetime of 780 ns. The TADF-OLEDs incorporating the ladder-oxaborin (deep-blue) and thiaborin (sky-blue) emitters achieved significantly high external electroluminescence quantum efficiencies of up to 20.1% and 25.9%, respectively, accompanied by suppressed efficiency roll-offs.