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Fukuta S.,Yamagata University | Wang Z.,Research Center for Organic Electronics | Miyane S.,Yamagata University | Koganezawa T.,Japan Synchrotron Radiation Research Institute | And 7 more authors.
Polymer Journal | Year: 2015

We report the synthesis and characterization of novel 1,3,4-thiadiazole (TDz)-containing π-conjugated alternating copolymers with donor units, such as thiophene (PTDzTh), selenophene (PTDzSe), thieno 3, 4-bthiophene (PTDzTT), 3,3′-didodecyl-2,2′-bithiophene (PTDzBTh) and (E)-1,2-di-(3-dodecylthiophene)vinylene (PTDzTV). The TDz-containing polymers show deep highest occupied molecular orbital (HOMO) energy levels at approximately-5.50 to-5.20 eV due to the electron deficiency of the TDz unit. In addition, PTDzTV shows a relatively extended absorption wavelength (λonset =629 nm). The microstructures of the film state are primarily influenced by the interdigitation of the side chains, and PTDzTT with a rigid backbone forms a densely packed crystalline structure, as evidenced by grazing incident wide-angle X-ray scattering experiments. Polymer solar cells using the TDz polymers showed high open-circuit voltages up to 0.965 V based on the deep HOMO energy levels, and PTDzTV showed the highest power conversion efficiency of 0.529% among the polymers. © 2015 The Society of Polymer Science, Japan (SPSJ) All rights reserved.

Tani Y.,Yamagata University | Tani Y.,Chiyoda Corporation | Seki T.,Chiba University | Seki T.,Chiyoda Corporation | And 9 more authors.
Molecular Crystals and Liquid Crystals | Year: 2013

The effect of doping carrier transporting materials being used for organic light emitting diodes was investigated in bulk-heterojunction photovoltaic devices composed of poly(3- hexylthiophene) (P3HT) and a perylene bisimide (PBI) derivative. We found that the doping of 4,4-bis(carbazol-9-yl)biphenyl (CBP) can improve the short circuit current and fill factor with a doping concentration of 2.5wt%, resulting in an increase of power conversion efficiency from 0.14% to 0.28%. This effect is mainly attributable to the improvement of miscibility between P3HT and PBI. Copyright © Taylor & Francis Group, LLC.

Ohashi C.,Yamagata University | Ohashi C.,Chiyoda Corporation | Yamada H.,Nara Institute of Science and Technology | Yamada H.,Chiyoda Corporation | And 3 more authors.
Molecular Crystals and Liquid Crystals | Year: 2013

6,13-pentacene diketone is a unique material which can be converted to pentacene only by photo irradiation. Drop-cast films of this soluble precursor of pentacene were prepared and their thin film properties were studied. The effect of solvent and photo irradiation conditions on photo-conversion behavior and film structures were investigated, compared to spin-cast films. The drop-cast films exhibited large plate-like crystals having a size of several microns, and showed intense peaks in X-ray diffraction. The electrical measurement using a field-effect transistor was also performed. © 2013 Taylor and Francis, LLC.

Shito K.,Yamagata University | Ito N.,Yamagata University | Masuhara A.,Yamagata University | Masuhara A.,Research Center for Organic Electronics | Masuhara A.,Research Institute for Tohoku Revitalization
Japanese Journal of Applied Physics | Year: 2015

We investigated the nanocrystallization of C60 in a reprecipitation method, which is very important in controlling the nanocrystal size. trans-Decahydronaphthalene and acetonitrile were used as good and poor solvents, respectively. With this combination, we can controlled the nanocrystallization process over a long time and elucidated the effects of compatibility speed between good and poor solvents after the reprecipitation method. 10μm particles of C60 micro/nanocrystals (C60 M/NCs) with a hollow spherical structure were observed. The surface of the C60 MCs of 10 μm size was composed of C60 nanocrystals of 50-150nm size coalesced with each other. Therefore, crystallization proceeds from the interface between the solution and the poor solvent. From this result, we showed that the scheme of the crystallization processes is divided into two processes after the reprecipitation method. © 2015 The Japan Society of Applied Physics.

Umetsu K.,Yamagata University | Akiba R.,Yamagata University | Nakayama K.,Yamagata University | Nakayama K.,Research Center for Organic Electronics | And 2 more authors.
Molecular Crystals and Liquid Crystals | Year: 2013

A hybrid metal-base organic transistor composed of a vacuum-deposited small-molecule emitter layer and a solution-processed polymer collector layer was fabricated using three types of conductive polymer, poly(3-hexylthiophene) (P3HT), poly(2-methoxy-5(2'-ethyl)hexoxy-phenylenevinylene (MEH-PPV) and poly(9, 9-dioctylfluorene-cobenzothiadiazole) (F8BT). Clear current amplification was observed only in the device with P3HT, and output current density of 12.6 mA/cm2 on/off ratio of 105, and current amplification factor of 76 were achieved at a collector voltage of 5 V and base voltage of 3 V. The output current decreased in order of P3HT > MEH-PPV > F8BT. The relationship between energy levels of polymer materials and carrier transmission process through the base electrode were discussed. © 2013 Taylor and Francis, LLC.

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