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 %.

A new entry of nBPhen-based n-type exciplex host partner realizes high efficiency and highly stable deep red phosphorescent organic light-emitting devices with an emission peak wavelength of 670 nm, and maximum external quantum efficiency of 17%.

Highly efficient and stable deep red OLED is successfully developed by using a BTBT-based p-type host material. This OLED exhibits higher efficiency, and over ×5 longer lifetime than that based on the conventional p-type host material, NPD.

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.

What is the most significant result of this study?Perfect horizontal orientation of the transition dipole moment (TDM) in the emitter molecule is one of the most important keys to boost the performances in organic light-emitting devices (OLEDs). Here, we were successfully able to find ak ey factor to control the TDM in triazine/acridine-based TADF emitters without loss of the photoluminescent quantum yield and realize high-performance sky-blue OLEDs with EQE of over 30%. Ak ey for success is that the small structural differences in triazine-based acceptor units make significant differences in device performances.

Although stable deep-red organic light-emitting devices (OLEDs) exhibit potential applications as unique illumination light sources for plant growth and in health monitoring systems, their electron-to-photon conversion efficiency, represented by the external quantum efficiency (EQE), is significantly lower than that of the other primary colors. Thus, to overcome this limitation, n-type exciplex host partners based on quinoline-modified phenanthroline derivatives, X-BPhen, were designed and synthesized in this study. These X-BPhen derivatives formed exciplexes on combination with a p-type host material, NPD, behaving as host materials in deep-red phosphorescent OLEDs. The corresponding devices exhibited a maximum EQE of 17.6%, with CIE coordinates of (0.71, 0.29), and an LT80 of 410 h at a constant current density of 25 mA/cm2; this is among the best performances reported for stable deep-red OLEDs.

Horizontally oriented thermally activated delayed fluorescent (TADF) emitters realizing high‐performance sky‐blue organic light‐emitting devices (OLEDs) are reported in this work. The cover image represents that triphenyltriazine‐based TADF emitters maximize the potential of sky‐blue TADF OLEDs. The small structural differences in acceptor units makes a significant differences to device performance. More information can be found in the Full Paper by H. Sasabe, J. Kido et al. (DOI: 10.1002/chem.20101188).