Katsuyuki Shizu

Thermally activated delayed fluorescence (TADF) emitters are promising dopants for organic light-emitting diodes, including those containing highly twisted donor–acceptor-type structures. However, highly twisted structures limit the variety of chemical structures applicable as TADF emitters. We present a strategy for designing electron donors that can eliminate this requirement and increase the structural diversity of TADF emitters. Using this strategy, we developed an electron donor containing

The use of thermally activated delayed-fluorescence (TADF) allows the realization of highly efficient organic light-emitting diodes (OLEDs) and is a promising alternative to the use of conventional fluorescence and phosphorescence. Recent research interest has focused on blue TADF emitters. In this study, we use quantum mechanics to reveal the relationship between the molecular structures and the photophysical properties of TADF emitters and derive a direction for the molecular design of highly

Molecules that exhibit multiple resonance (MR) type thermally activated delayed fluorescence (TADF) are highly efficient electroluminescent materials with narrow emission spectra. Despite their importance in various applications, the emission mechanism is still controversial. Here, a comprehensive understanding of the mechanism for a representative MR-TADF molecule (5,9-diphenyl-5,9-diaza-13b-boranaphtho[3,2,1-de]anthracene, DABNA-1) is presented. Using the equation-of-motion coupled-cluster sin

Thermally activated delayed-fluorescence (TADF) emitters have attracted increasing attention as third-generation electroluminescent materials for organic light-emitting diodes. This study presents a design strategy for highly efficient TADF emitters, guided by quantum-chemistry calculations of radiative and nonradiative decay rates. By optimizing HOMO-LUMO overlap density and suppressing nonradiative decay, the authors develop a purely organic emitter with very high quantum yields from photolumi

Abstract Thermally activated delayed fluorescence (TADF) emitters are third-generation electroluminescent materials that realize highly efficient organic light-emitting diodes (OLEDs) without using rare metals. Here, after briefly reviewing the principles of TADF and its use in OLEDs, we report a sky-blue TADF emitter, 9-(4-(benzo[ d ]thiazol-2-yl)phenyl)- N 3 , N 3 , N 6 , N 6 -tetraphenyl-9 H -carbazole-3,6-diamine (DAC-BTZ). DAC-BTZ is a purely organic donor–acceptor-type molecule with a smal

A cost-effective method of theoretically predicting electronic-transition rate constants from the excited states of molecules is reported. This method is based on density functional theory calculations of electronic states and quantitative rate constant determination with the Fermi golden rule. The method is applied to the theoretical determination of the excited-state decay mechanism of photoexcited benzophenone, a representative molecule in photochemistry and biochemistry. Calculated rate cons

Many phenomena in nature consist of multiple elementary processes. If we can predict all the rate constants of respective processes quantitatively, we can comprehensively predict and understand various phenomena. Here, we report that it is possible to quantitatively predict all related rate constants and quantum yields without conducting experiments, using multiple-resonance thermally activated delayed fluorescence (MR-TADF) as an example. MR-TADFs are excellent emitters because of its narrow em

Thermally activated delayed fluorescence (TADF) molecules are promising for realizing durable organic light-emitting diodes in all color regions. Fast reverse intersystem crossing (RISC) is a way of improving the device lifetime of TADF-based organic light-emitting diodes. To date, RISC rate constants (<i>k</i>_RISC) of 10⁸ s^-1 have been reported for metal-free TADF molecules. Here, we report the heavy-atom effect on TADF and a molecular design for further promoti

We theoretically propose a boron-containing molecule, hexaboracyclophane (HBCP), as an electron-transporting (ET) material with low-power loss. We calculate the vibronic coupling of HBCP, comparing them with those of other ET materials, tris-(8-hydroxyquinoline) aluminum(III) (Alq3) and tris[3-(3-pyridyl)mesityl]borane (3TPYMB). Using the nonequilibrium Green’s function method to evaluate their single molecular ET properties, we show that HBCP exhibits more efficient and lower-power consumption

We theoretically propose a hole-transporting molecule, hexaaza[16]parabiphenylophane (HAPBP), on the basis of vibronic coupling density (VCD). We calculate vibronic coupling constants (VCCs) of HAPBP and compare them with those of other well-known hole-transporting materials, N,N′-bis(3-methylphenyl)-N,N′-diphenyl[1,1′-biphenyl]-4,4′-diamine (TPD), N,N,N′,N′-tetraphenylbenzidine (TAD), and N,N′-di(1-naphthyl)-N,N′-diphenyl[1,1′-biphenyl]-4,4′-diamine (α-NPD). HAPBP has smaller VCCs than TPD, TAD

Thermally activated delayed fluorescence (TADF) emitters have recently attracted considerable attention as dopants for organic light-emitting diodes (OLEDs), and are considered promising alternatives to fluorescent and phosphorescent dopants. TADF emitters require a small singlet-triplet energy gap (ΔEST). This study presents a molecular design strategy to achieve a small ΔEST. An electroluminescent dopant containing two electron-donating carbazolyl groups and an electron-accepting triphenyltria

Tetracene-based singlet fission (SF) materials show application prospects as triplet sensitizers in organic optoelectronics. SF involves internal conversion from photoexcited singlet states ¹(S₁S₀) to correlated triplet pair states ¹(T₁T₁). We derive an expression for the internal conversion rate on the basis of the Fermi golden rule with an artificial Lorentzian broadening. The internal conversion rate depends on the interstate v