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-1 ), and showed blue emission with a peak wavelength of ∼465 nm and a high photoluminescence quantum yield that ranges up to 81 %. Notably, these emitters are suitable for fabricating both evaporation- and solution-based systems. The evaporation-based system OLED achieved a high external quantum efficiency (EQE) of 5.4 %. While the solution-processed system realized 4.8 %, exhibiting the best performance among the anthracene-based solution-processed OLEDs so far.

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 10.1002/chem.202101188.

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. Here, to obtain insights for further improvements of a triazine/acridine combination, various asymmetric spirobiacridine (SBA)-based TADF emitters with a unity photoluminescence quantum yield and high Θ ratio of over 80 % were developed. Furthermore, the substitution effects of the triazine acceptor unit on the photophysical properties were studied, including molecular orientations and OLED performance. The corresponding OLED exhibited sky-blue emission with a high EQE of over 30 %.