Takumi Shibata

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Organic light-emitting diodes (OLEDs) are attractive for next-generation displays and lighting applications because of their potential for high electroluminescence (EL) efficiency, flexibility and low-cost manufacture. Although phosphorescent emitters containing rare metals such as iridium or platinum produce devices with high EL efficiency, these metals(More)
Red fluorescent molecules suffer from large, non-radiative internal conversion rates (k(IC)) governed by the energy gap law. To design efficient red thermally activated delayed fluorescence (TADF) emitters for organic light-emitting diodes (OLEDs), a large fluorescence rate (k(F)) as well as a small energy difference between the lowest singlet and triplet(More)
Since 2007, the Telescope Array (TA) experiment, based in Utah, USA, has been observing ultra high energy cosmic rays to understand their origins. The experiment involves a surface detector (SD) array and three fluores-cence detector (FD) stations. FD stations, installed surrounding the SD array, measure the air fluorescence light emitted from extensive air(More)
A/sub 0.26/Ga/sub 0.74/N/AlN/GaN heterostructures with 1-nm-thick AlN interfacial layers were grown on 100-mm-diameter epitaxial AlN/sapphire templates and sapphire substrates by metalorganic vapor phase epitaxy (MOVPE). Very high Hall mobilities of approximately 2100 cm/sup 2//Vs at room temperature and approximately 25000 cm/sup 2//Vs at 15 K with a 2DEG(More)
We evaluate the exposure during nadir observations with JEM-EUSO, the Extreme Universe Space Observatory, on-board the Japanese Experiment Module of the International Space Station. Designed as a mission to explore the extreme energy Universe from space, JEM-EUSO will monitor the Earth's nighttime atmosphere to record the ultraviolet light from tracks(More)
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