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    The purpose of the present invention is to provide an organic EL element which has an emission peak in the near infrared region and which exhibits high luminous efficiency. This organic EL element has: an anode; a cathode; and at least one organic layer, including a light-emitting layer, disposed between the anode and cathode. The light-emitting layer contains a first organic compound, a second organic compound, and a third organic compound that satisfy formula (i) and formula (ii). Formula (i): ES1(A) > ES1(B) > ES1(C). Formula (ii): ET1(A) > ET1(B). The second organic compound is a delayed luminous material for which ΔEST is 0.3 eV or less, and the third organic compound is a luminous material which is represented by formula (1) and for which the maximum emission wavelength in a fluorescence spectrum falls within the range 700-1000 nm.
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  • Sub-Microsecond TADF Emission in D-D芒聙聶-A Emitters

    Auffray, Morgan   Balijapalli, Umamahesh   Ribierre, Jean-Charles   Tsuchiya, Youichi   Adachi, Chihaya  

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  • Origin of dual emission in σ-bridged donor–acceptor TADF compounds

    Skaisgiris, Rokas   Serevičius, Tomas   Kazlauskas, Karolis   Geng, Yan   Adachi, Chihaya   Juršėnas, Saulius  

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  • Deep-Red Amplified Spontaneous Emission from cis-Configured Squaraine

    Ye, Hao   Cui, Linsong   Matsushima, Toshinori   Qin, Chuanjiang   Adachi, Chihaya  

    We report deep-red amplified spontaneous emission (ASE) from cis-configured squaraine (cis-DCSQ1) under optical pumping. Doping of cis-DCSQ1 into a 4,4'-bis(9-carbazolyl)-2,2'-biphenyl (CBP) host film at an appropriate concentration (0.5 wt % for this system) led to a marked increase of photoluminescence quantum yield because of efficient CBP-to-cis-DCSQ1 Forster resonance energy transfer and suppression of aggregation caused quenching. Thus, this doped film showed clear ASE with a threshold of around 10 mu J cm(-2) and peak wavelength of 687 nm. These results proved that cis-configured squaraine derivatives are promising as gain materials for future applications as deep-red organic lasers.
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  • High performance from extraordinarily thick organic light-emitting diodes

    Matsushima, Toshinori   Bencheikh, Fatima   Komino, Takeshi   Leyden, Matthew R.   Sandanayaka, Atula S. D.   Qin, Chuanjiang   Adachi, Chihaya  

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  • Many Exciplex Systems Exhibit Organic Long‐Persistent Luminescence

    Nishimura, Naohiro   Lin, Zesen   Jinnai, Kazuya   Kabe, Ryota   Adachi, Chihaya  

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    [Problem] To provide: a host compound for a light-emitting layer, wherein the compound is a material for a highly efficient organic electroluminescence device, has a high excited triplet level, is capable of completely confining triplet excitons of phosphorescent and thermally activated delayed fluorescence (TADF) emitters, and has excellent thin film stability, i.e., has a high glass transition point (Tg); and a highly efficient and highly luminescent organic electroluminescence device using the compound. [Solution] The present invention provides an organic electroluminescence device which has a pair of electrodes and at least one organic layer sandwiched therebetween, the organic electroluminescence device being characterized in that the organic layer is a light-emitting layer, and a compound having an azacarbazole structure represented by general formula (1) is used as a material constituting the light-emitting layer.
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  • Toward continuous-wave operation of organic semiconductor lasers

    Sandanayaka, Atula S. D.   Matsushima, Toshinori   Bencheikh, Fatima   Yoshida, Kou   Inoue, Munetomo   Fujihara, Takashi   Goushi, Kenichi   Ribierre, Jean-Charles   Adachi, Chihaya  

    The demonstration of continuous-wave lasing from organic semiconductor films is highly desirable for practical applications in the areas of spectroscopy, data communication, and sensing, but it still remains a challenging objective. We report low-threshold surface-emitting organic distributed feedback lasers operating in the quasicontinuous-wave regime at 80 MHz as well as under long-pulse photoexcitation of 30 ms. This outstanding performance was achieved using an organic semiconductor thin film with high optical gain, high photoluminescence quantum yield, and no triplet absorption losses at the lasing wavelength combined with a mixed-order distributed feedback grating to achieve a low lasing threshold. A simple encapsulation technique greatly reduced the laser-induced thermal degradation and suppressed the ablation of the gain medium otherwise taking place under intense continuous-wave photoexcitation. Overall, this study provides evidence that the development of a continuous-wave organic semiconductor laser technology is possible via the engineering of the gain medium and the device architecture.
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  • Organic long persistent luminescence

    Kabe, Ryota   Adachi, Chihaya  

    Long persistent luminescence (LPL) materials-widely commercialized as 'glow-in-the-dark' paints-store excitation energy in excited states that slowly release this energy as light(1). At present, most LPL materials are based on an inorganic system of strontium aluminium oxide (SrAl2O4) doped with europium and dysprosium, and exhibit emission for more than ten hours(2). However, this system requires rare elements and temperatures higher than 1,000 degrees Celsius during fabrication, and light scattering by SrAl2O4 powders limits the transparency of LPL paints(1). Here we show that an organic LPL (OLPL) system of two simple organic molecules that is free from rare elements and easy to fabricate can generate emission that lasts for more than one hour at room temperature. Previous organic systems, which were based on two-photon ionization, required high excitation intensities and low temperatures(3). By contrast, our OLPL system-which is based on emission from excited complexes (exciplexes) upon the recombination of long-lived charge-separated states-can be excited by a standard white LED light source and generate long emission even at temperatures above 100 degrees Celsius. This OLPL system is transparent, soluble, and potentially flexible and colour-tunable, opening new applications for LPL in large-area and flexible paints, biomarkers, fabrics, and windows. Moreover, the study of long-lived charge separation in this system should advance understanding of a wide variety of organic semiconductor devices(4).
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    [Problem] To provide, as a material for highly efficient organic electroluminescent elements, a light emitting material, specifically a host material for a light emitting layer, comprising a compound having a high excited triplet level; and an organic electroluminescent element which uses this material and has high efficiency and high luminance. [Solution] A light emitting material which is composed of a compound having a carbazole ring structure represented by general formula (1); and an organic electroluminescent element which is composed of a pair of electrodes and one or more layers that are sandwiched between the electrodes and include at least a light emitting layer, and which is characterized in that the above-described light emitting material is used as a constituent material for the light emitting layer.
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    An organic EL material according to the present invention is formed of a compound represented by general formula (I). In formula (I), each of R1 and R2 is, independently of each other, a hydrogen atom or an arbitrary substituent, and it is preferable that R1 and R2 be substituents selected from a group including the hydrogen atom, cyano groups, halogen-substituted alkyl groups, halogens, pyridyl groups that may include a substituent, and electron-donating aromatic groups. A is a substituent in which at least one heteroaryl group that may include a substituent or aryl amino group that may include a substituent is bonded, directly or via another aromatic group, to the carbon at the 4 position of a pyridine ring.
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  • Two Regimes of Carrier Diffusion in Vapor-Deposited Lead-Halide Perovskites

    Scajev, Patrik   Aleksiejunas, Ramunas   Miasojedovas, Saulius   Nargelas, Saulius   Inoue, Munetomo   Qin, Chuanjiang   Matsushima, Toshinori   Adachi, Chihaya   Jursenas, Saulius  

    Metal halide perovskites are attractive materials for the realization of cheap and effective solar cells, thin film transistors, and light emitters. Carrier diffusion at high excitations, however, is poorly addressed in perovskites, even though it governs the diffusion length and determines the efficiency of photonic devices. To fully understand the dependence of diffusion length on carrier density, we performed direct and independent measurements of the carrier diffusion coefficient and recombination rate in several methylammonium lead halide perovskite layers by applying the light-induced transient grating technique. We demonstrate the existence of two distinct carrier diffusion regimes within the density range of 10(18)-10(20) cm(-3). In the perovskite films of high compositional quality, diffusion is governed by a bandlike transport of free carriers. The diffusivity is high (0.28-0.7 cm(2)/s) in these samples, even at low carrier density, and further increases with excitation due to carrier degeneracy. The opposite scenario was observed in disordered perovskite layers, where diffusion is governed by hopping-like transport of localized carriers. The diffusion coefficient in latter layers is small (0.01-0.04 cm(2)/s at low densities) and increases with excitation due to local state filling and carrier delocalization. We show that carrier recombination can be well-described using the nonlinear radiative and nonradiative recombination coefficients that saturate with excitation due to phase space filling at high carrier densities. On the basis of these findings, we provide recommendations for the maximization of carrier diffusion length in different perovskites.
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  • Large metal halide perovskite crystals for field-effect transistor applications

    Matsushima, Toshinori   Leyden, Matthew R.   Fujihara, Takashi   Qin, Chuanjiang   Sandanayaka, Atula S. D.   Adachi, Chihaya  

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  • Thermally Activated Delayed Fluorescence from Pentacarbazorylbenzonitrile

    Tanimoto, Shuho   Suzuki, Takatsugu   Nakanotani, Hajime   Adachi, Chihaya  

    A benzonitrile derivative substituted by five carbazoles (5CzBN), which emits thermally activated delayed fluorescence (TADF), was synthesized and evaluated. The organic light-emitting diode (OLED) containing 5CzBN demonstrated light-blue electro-luminescence and a high external quantum efficiency of 14.8%.
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  • Afterglow Organic Light-Emitting Diode

    Kabe, Ryota   Notsuka, Naoto   Yoshida, Kou   Adachi, Chihaya  

    An afterglow organic light-emitting diode (OLED) that displays electroluminescence with long transient decay after it is turned off is demonstrated. This OLED exhibits blue and green dual emission originating from fluorescence and phosphorescence, respectively. A phosphorescence lifetime of 4.3 s is achieved.
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  • A Phenazaborin-Based High-Efficiency Blue Delayed Fluorescence Material

    Park, In Seob   Numata, Masaki   Adachi, Chihaya   Yasuda, Takuma  

    A highly efficient blue thermally activated delayed fluorescence (TADF) material based on phenazaborin and spiroacridan units was developed. A blue-emitting organic light-emitting diode containing the phenazaborin derivative as a TADF emitter exhibited a high external electro-luminescence quantum efficiency of 18.2%.
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