Nonbonding/Bonding Molecular Orbital Regulation of Nitrogen-Boron-Oxygen-embedded Blue/Green Multiresonant TADF Emitters with High Efficiency and Color Purity.

Invited for the cover of this issue is the group of H. Sasabe and J. Kido at Yamagata University in Japan.

Nonbonding/Bonding Molecular Orbital Regulation of Nitrogen-Boron-Oxygen-embedded Blue/Green Multiresonant TADF Emitters with High Efficiency and Color Purity.

In this study, we synthesized and characterized multiresonant thermally activated delayed fluorescent (TADF) materials embedded with nitrogen-boron-oxygen (N-B-O), exhibiting color-tunability between blue and green, namely NBO, m-DiNBO, and p-DiNBO. The three emitter materials showed a high photoluminescence quantum yield (PLQY) and a state-of-the-art narrow full width at half maximum (FWHM) of 96 %/25 nm, 87 %/17 nm, and 99 %/19 nm, respectively. For m-DiNBO and p-DiNBO, the emission color could be tuned from blue to green by regulating the nonbonding/bonding molecular orbital characters.

Constructing Soluble Anthracene-Based Blue Emitters Free of Electrically Inert Alkyl Chains for Efficient Evaporation- and Solution-Based OLEDs.

Anthracene derivatives are one of the most promising blue emitters employed in organic light-emitting devices (OLEDs) because of their electrochemical and thermal stabilities. However, their high crystallinity owing to their large π-planar structures severely impedes the progress in the development of solution-based systems. In this work, we developed two types of highly soluble multifunctional anthracene derivatives terminated with ortho-biphenyl and triphenylamine moieties and showed high solubility in general organic solvents such as toluene, tetrahydrofuran, and cyclohexanone at high concentrations (>10 mg mL ), and showed blue emission with a peak wavelength of ∼465 nm and a high photoluminescence quantum yield that ranges up to 81 %.

Four Dibenzofuran-Terminated High-Triplet-Energy Hole Transporters for High-Efficiency and Long-Life Organic Light-Emitting Devices.

The weak stability of a hole-transporter upon approaching the anion state is one of the major bottlenecks for developing long-life organic light-emitting devices (OLEDs). Therefore, in this study, we developed a series of thermally and electrically stable hole-transporters that are end-capped with four dibenzofuran units. These materials exhibit i) high bond dissociation energy (BDE) toward the anion state, ii) a high glass transition temperature (T >130 °C), and iii) high triplet energy (E >2.

Asymmetric Spirobiacridine-based Delayed Fluorescence Emitters for High-performance Organic Light-Emitting Devices.

Invited for the cover of this issue is Hisahiro Sasabe, Junji Kido and co-workers at Yamagata University in Japan. This image depicts that the chemical structure of the acceptor is one of the most important keys to maximize the potential of triazine/acridine-based thermally activated delayed fluorescence (TADF) emitters realizing high external quantum efficiency (EQE) of over 30%. Read the full text of the article at 10.

Asymmetric Spirobiacridine-based Delayed Fluorescence Emitters for High-performance Organic Light-Emitting Devices.

Recently, researchers have focused on thermally activated delayed fluorescence (TADF) for efficient future lighting and displays. Among TADF emitters, a combination of triazine and acridine is a promising candidate for realizing high-efficiency organic light-emitting devices (OLEDs). However, simultaneous development of perfect horizontal orientation (Θ=100 %) and an external quantum efficiency (EQE) of over 40 % is still challenging.