Faculty Profiles - AKIYAMA Tsuyoshi

Papers - AKIYAMA Tsuyoshi

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Insertion effect of spin-coated films of C<inf>60</inf>-ethylenediamine adduct on organic thin-film solar cells Reviewed

Yamada A., Izumoto D., Akiyama T., Fujita K., Suzuki A., Oku T.

AIP Conference Proceedings 1929 2018.1

Language：English Publishing type：Research paper (scientific journal) Publisher：AIP Conference Proceedings

C -ethylanediamine adduct particle (C P) were prepared by simply mixing of C and ethylenediamine (EDA) in toluene. C P was dissolved into EDA to obtain C P-EDA. C P-EDA can be diluted by ethanol, 2-methoxyethanol or water. Thin films of C P-EDA were prepared from these diluted solutions of C P-EDA by spin-coating. Such thin-films were used as a part of organic thin-film solar cells. 60 60 60 60 60 60 60 60

DOI： 10.1063/1.5021933

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Effect of gold nanoparticles in titanium oxide layer on the photovoltaic performance of inverted-type organic thin-film solar cells Reviewed

Tsuyoshi Akiyama*, Hiroki Sakata, Taisuke Matsumoto, Shota Mitsukawa, Hiroshi Sakaguchi, and Takeo Oku

Molecular Crystals and Liquid Crystals 653 50 - 56 2017.11

Effect of gold nanoparticles in titanium oxide layer on the photovoltaic performance of inverted-type organic thin-film solar cells Reviewed

Akiyama T., Sakata H., Matsumoto T., Mitsukawa S., Sakaguchi H., Oku T.

Molecular Crystals and Liquid Crystals 653 ( 1 ) 50 - 56 2017.8

Language：English Publishing type：Research paper (scientific journal) Publisher：Molecular Crystals and Liquid Crystals

© 2017 Taylor & Francis Group, LLC. Gold nanoparticle/titanium oxide composite materials were prepared at low temperature and were used as electron-transport layers for inverted-type organic thin-film solar cells. The application of gold nanoparticle/titanium oxide composite materials led to an improvement in the photoelectric conversion efficiency of the solar cells under simulated sunlight irradiation.

DOI： 10.1080/15421406.2017.1348843

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Morphological change of crystalline polymer films by annealing: substrate- and heating/cooling-rate-dependent surface roughness Reviewed

Uto Y., Mizobata K., Maurya S., Akiyama T., Nakajima T.

Surface and Interface Analysis 49 ( 7 ) 577 - 583 2017.7

Language：English Publishing type：Research paper (scientific journal) Publisher：Surface and Interface Analysis

Copyright © 2017 John Wiley & Sons, Ltd. We study the morphological change of crystalline polymer films by annealing using atomic force microscope, X-ray diffraction, and Fourier transform infrared spectroscopy techniques. As typical samples, we employ high-density and low-density polyethylene films prepared by the cast method. After annealing at 135 °C for 4 h, the surface roughness of polyethylene films by the atomic force microscope significantly increases, and the crystallite size by the X-ray diffraction also shows some increase, while the Fourier transform infrared spectroscopy spectrum hardly exhibits any change. This can be well explained as a result of the growth of crystal structure by recrystallization during annealing. More interestingly, we find that the choice of the substrate and also the heating/cooling rates for annealing significantly influences the surface roughness of the films. Copyright © 2017 John Wiley & Sons, Ltd.

DOI： 10.1002/sia.6195

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Development of Plasmonic Cu<inf>2</inf>O/Cu Composite Arrays as Visible- and Near-Infrared-Light-Driven Plasmonic Photocatalysts Reviewed

Sugawa K., Tsunenari N., Takeda H., Fujiwara S., Akiyama T., Honda J., Igari S., Inoue W., Tokuda K., Takeshima N., Watanuki Y., Tsukahara S., Takase K., Umegaki T., Kojima Y., Nishimiya N., Fukuda N., Kusaka Y., Ushijima H., Otsuki J.

Langmuir 33 ( 23 ) 5685 - 5695 2017.6

Language：English Publishing type：Research paper (scientific journal) Publisher：Langmuir

We describe efficient visible- and near-infrared (vis/NIR) light-driven photocatalytic properties of hybrids of Cu O and plasmonic Cu arrays. The Cu O/Cu arrays were prepared simply by allowing a Cu half-shell array to stand in an oxygen atmosphere for 3 h, which was prepared by depositing Cu on two-dimensional colloidal crystals with a diameter of 543 or 224 nm. The localized surface plasmon resonances (LSPRs) of the arrays were strongly excited at 866 and 626 nm, respectively, at which the imaginary part of the dielectric function of Cu is small. The rate of photodegradation of methyl orange was 27 and 84 times faster, respectively, than that with a Cu O/nonplasmonic Cu plate. The photocatalytic activity was demonstrated to be dominated by Cu LSPR excitation. These results showed that the inexpensive Cu O/Cu arrays can be excellent vis/NIR-light-driven photocatalysts based on the efficient excitation of Cu LSPR. 2 2 2 2

DOI： 10.1021/acs.langmuir.7b01052

Scopus

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Effects of PBr3 Addition to Polysilane Thin Films on Structures and Photovoltaic Properties Reviewed International journal

Junya Nakagawa, Takeo Oku, Atsushi Suzuki, Tsuyoshi Akiyama, Masahiro Yamada, Sakiko Fukunishi, Kazufumi Kohno

Green and Sustainable Chemistry 2017.2

Cathode buffer composed of fullerene-ethylenediamine adduct for an organic solar cell Reviewed

Kimoto Y., Akiyama T., Fujita K.

Japanese Journal of Applied Physics 56 ( 2 ) 2017.2

Language：English Publishing type：Research paper (scientific journal) Publisher：Japanese Journal of Applied Physics

We developed a fullerene-ethylenediamine adduct (C P-DC) for a cathode buffer material in organic bulk heterojunction solar cells, which enhance the open-circuit voltage (V ). The evaporative spray deposition using ultra dilute solution (ESDUS) technique was employed to deposit the buffer layer onto the organic active layer to avoid damage during the deposition. By the insertion of a C P-DC buffer layer, V and power conversion efficiency (PCE) were increased from 0.41 to 0.57 V and from 1.65 to 2.10%, respectively. The electron-only device with the C P-DC buffer showed a much lower current level than that without the buffer, indicating that the V increase is caused not by vacuum level shift but by hole blocking. The curve fitting of current density-voltage (J-V) characteristics to the equivalent circuit with a single diode indicated that the decrease in reversed saturation current by hole blocking increased caused the V . 60 oc 60 oc 60 oc oc

DOI： 10.7567/JJAP.56.021601

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Doping effects of transition metal elements to titanium dioxide for perovskite solar cells Reviewed

Saito J., Suzuki A., Akiyama T., Oku T.

AIP Conference Proceedings 1807 2017.1

Language：English Publishing type：Research paper (scientific journal) Publisher：AIP Conference Proceedings

Organic-inorganic hybrid heterojunction solar cells containing perovskite CH NH PbI using Nb, Ta, or V-doped TiO as electron-transporting layers were fabricated and characterized. By Nb doping, the conductivity and carrier density of the TiO increased, and its flat-band potential showed a positive shift. The short-circuit current density and power conversion efficiency of perovskite solar cells were improved by using Ti Nb O compared to undoped TiO . 3 3 3 2 2 0.95 0.05 2 2

DOI： 10.1063/1.4974792

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Fabrication and electrochemical properties of insoluble fullerene-diamine adduct thin-films as buffer layer by alternate immersion process Reviewed

Saito J., Akiyama T., Suzuki A., Oku T.

AIP Conference Proceedings 1807 2017.1

Language：English Publishing type：Research paper (scientific journal) Publisher：AIP Conference Proceedings

Insoluble fullerene-diamine adduct thin-films consisting of C and 1,2-diaminoethane were easily fabricated on an electrode by an alternate immersion process. Formation of the C -diamine adduct films were confirmed using transmission absorption spectroscopy and atomic force microscopy. An inverted-type organic solar cells were fabricated by using the C -diamine adduct film as the electron transport layer. The resultant photoelectric conversation performance of the solar cells suggested that photocurrent is generated via the photoexcitation of polythiophene. The result suggests that the present insoluble fullerene-diamine adduct films worked as buffer layer for organic thin-film solar cells. 60 60 60

DOI： 10.1063/1.4974799

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Retardation of sol–gel titanium oxide with imprinted grating structure Reviewed International journal

Itsunari Yamada, Yoshiro Ishihara, Tsuyoshi Akiyama

Optical Engineering 56 ( 1 ) 017108 2017.1

Cathode buffer composed of fullerene–ethylenediamine adduct for an organic solar cell Reviewed International journal

Yoshinori Kimoto, Tsuyoshi Akiyama, Katsuhiko Fujita

Japanese Journal of Applied Physics 56 021601 2017.1

Fabrication and Characterization of PCBM: P3HT-based Thin-film Organic Solar Cells with Zinc Phthalocyanine and 1,8-Diiodooctane Reviewed International journal

Haruto Maruhashi, Takeo Oku, Atsushi Suzuki, Tsuyoshi Akiyama, Yasuhiro Yamasaki

Chemical and Materials Engineering 5 ( 1 ) 1 - 7 2017

Fabrication and electrochemical properties of insoluble fullerene-diamine adduct thin- films as buffer layer by alternate immersion process Reviewed International journal

Jo Saito, Tsuyoshi Akiyama, Atsushi Suzuki, Takeo Oku

AIP Conference Proceedings 1807 020017 2017

Doping effects of transition metal elements to titanium dioxide for perovskite solar cells Reviewed International journal

Jo Saito, Atsushi Suzuki, Tsuyoshi Akiyama, Takeo Oku

AIP Conference Proceedings 1807 020010 2017

Efficient Photocurrent Enhancement from Porphyrin Molecules on Plasmonic Copper Arrays: Beneficial Utilization of Copper Nanoanntenae on Plasmonic Photoelectric Conversion Systems Reviewed International journal

Kosuke Sugawa, Daisuke Yamaguchi, Natsumi Tsunenari, Koji Uchida, Hironobu Tahara, Hideyuki Takeda, Kyo Tokuda, Shota Jin, Yasuyuki Kusaka, Nobuko Fukuda, Hirobumi Ushijima, Tsuyoshi Akiyama, Yasuhiro Watanuki, Nobuyuki Nishimiya, Joe Otsuki, Sunao Yamada

ACS Applied Materials and Interfaces 9 750 - 762 2016.12

Extraordinary enhancement of porphyrin photocurrent utilizing plasmonic silver arrays Reviewed

Sugawa K., Uchida K., Takeshima N., Jin S., Tsunenari N., Takeda H., Kida Y., Akiyama T., Otsuki J., Takase K., Yamada S.

Nanoscale 8 ( 34 ) 15467 - 15472 2016.9

Language：English Publishing type：Research paper (scientific journal) Publisher：Nanoscale

We demonstrate up to ∼630-fold enhancement of the photocurrent from a porphyrin monolayer on a plasmonic Ag-array electrode showing plasmon absorption in the Q-band region relative to that on a planar Ag electrode. The photocurrent obtained by the Q-band excitation in the plasmonic electrodes even exceeded that obtained by the Soret-band excitation in a normal, nonplasmonic electrode.

DOI： 10.1039/c6nr03158g

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Extraordinary enhancement of porphyrin photocurrent utilizing plasmonic silver arrays Reviewed International journal

Kosuke Sugawa*, Koji Uchida, Naoto Takeshima, Shota Jin, Natsumi Tsunenari, Hideyuki Takeda, Yuki Kida, Tsuyoshi Akiyama, Joe Otsuki, Kouichi Takase, Sunao Yamada

Nanoscale 8 15467 - 15472 2016.7

Fabrication and Photocurrent Generation Properties of Insoluble Hierarchical Polythiophene Thin Films Prepared by Sequential Electrochemical Polymerization Reviewed International journal

Yu Kumagawa, Tsuyoshi Akiyama*, Yuki Nishimura, Koji Goto, Atsushi Suzuki, Takeo Oku

Bulletin of the Chemical Society of Japan 89 700 - 704 2016.6

Low-temperature synthesis of titanium oxide/gold nanoparticle composite powders using a combination of the sol–gel process and ultraviolet light irradiation Reviewed

Matsumoto T., Akiyama T., Banya S., Izumoto D., Sakaguchi H., Oku T.

Journal of Sol-Gel Science and Technology 78 ( 3 ) 692 - 697 2016.6

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Sol-Gel Science and Technology

Abstract: Amorphous titanium oxide/plasmonic gold nanoparticle composite powders were synthesized by a combination of the sol–gel process and ultraviolet light irradiation using light-emitting diode at room temperature. The resultant composite powders were dried at ~50 °C. These amorphous titanium oxide/gold nanoparticle composite powders were heated to 450 °C to obtain crystalline titanium oxide/gold nanoparticles. The formation and microstructure of the titanium oxide/gold nanoparticle composite powders were confirmed by transmission electron microscopy, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, thermo gravimetry–differential thermal analysis, and optical absorption measurements. A clear plasmonic absorption band due to typical plasmonic gold nanoparticle was observed in both composite powders. Graphical Abstract: [Figure not available: see fulltext.]

DOI： 10.1007/s10971-016-3990-7

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Low-temperature synthesis of titanium oxide/gold nanoparticle composite powders using a combination of the sol–gel process and ultraviolet light irradiation Reviewed International journal

Taisuke Matsumoto, Tsuyoshi Akiyama*, Shoto Banya, Daisuke Izumoto, Hiroshi Sakaguchi, Takeo Oku

Journal of Sol-Gel Science and Technology 78 692 - 697 2016.3

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Papers - AKIYAMA Tsuyoshi