Faculty Profiles - AKIYAMA Tsuyoshi

Papers - AKIYAMA Tsuyoshi

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Fabrication and Characterization of PCBM:P3HT Bulk Heterojunction Solar Cells Doped with Germanium Phthalocyanine or Germanium Naphthalocyanine（共著） Reviewed

Yoshida, Kazumi; Oku, Takeo*; Suzuki, Atsushi; Akiyama, Tsuyoshi; Yamasaki, Yasuhiro.

Materials Sciences and Applications 4 1 - 5 2013.4

Microstructure Analysis and Properties of Anti-Reflection Thin Films for Spherical Silicon Solar Cells（共著） Reviewed

Kanayama, Masato; Oku, Takeo*; Akiyama, Tsuyoshi; Kanamori, Youichi; Seo, Satoshi; Takami, Jun; Ohnishi, Yoshimasa; Ohtani, Yoshikazu; Murozono, Mikio.

Energy and Power Engineering 5 18 - 22 2013.4

Fabrication and Characterization of PCBM:P3HT Bulk Heterojunction Solar Cells Doped with Germanium Phthalocyanine or Germanium Naphthalocyanine（共著） Reviewed

Yoshida, Kazumi; Oku, Takeo*; Suzuki, Atsushi; Akiyama, Tsuyoshi; Yamasaki, Yasuhiro.

Materials Sciences and Applications 4 1 - 5 2013.4

Incorporation effect of silver nanoparticles on inverted type bulk-heterojunction organic solar cells Reviewed

Matsumoto T., Oku T., Akiyama T.

Japanese Journal of Applied Physics 52 ( 4 PART 2 ) 2013.4

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

A series of bulk-heterojunction organic solar cells incorporating silver nanoparticles was fabricated and evaluated. Silver nanoparticles were incorporated in the hole-transport layer of the solar cells. Plasmonic absorption and the generation of localized surface plasmon resonance of silver nanoparticles were confirmed by absorption and surface enhanced Raman scattering spectra even in the hole-transport material. The incorporation of silver nanoparticles increased photoelectric conversion efficiencies, whose enhancement properties were varied by the incorporation amount of silver nanoparticles. © 2013 The Japan Society of Applied Physics.

DOI： 10.7567/JJAP.52.04CR13

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Microstructures and photovoltaic properties of polysilane-based solar cells Reviewed

Oku T., Nakagawa J., Iwase M., Kawashima A., Yoshida K., Suzuki A., Akiyama T., Tokumitsu K., Yamada M., Nakamura M.

Japanese Journal of Applied Physics 52 ( 4 PART 2 ) 2013.4

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

Polysilane-based organic solar cells with bulk heterojunction and heterojunction structures were fabricated by spin-coating using a mixture solution. Microstructures of the solar cells were investigated by X-ray diffraction analysis and transmission electron microscopy, which indicated a nanocomposite and amorphous structure. The effects of phosphorus and boron doping into polysilanes were investigated by electrical measurements, Raman scattering analysis and Hall effect measurements. Here, we discuss the photovoltaic properties and microstructures of the solar cells. Energy levels in the present solar cells are also discussed. © 2013 The Japan Society of Applied Physics.

DOI： 10.7567/JJAP.52.04CR07

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Fabrication and characterization of polysilane: PCBM bulk heterojunction solar cells（共著） Reviewed

Yoshida, Kazumi; Oku, Takeo*; Suzuki, Atsushi; Akiyama, Tsuyoshi; Tokumitsu, Katsuhisa; Nakamura, Mika; Yamada Masahiro.

Central European Journal of Engineering 3 165 - 169 2013.4

Microstructures and photovoltaic properties of polysilane-based solar cells（共著） Reviewed

Oku, Takeo*; Nakagawa, Junya; Iwase, Makoto; Kawashima, Atsushi; Yoshida, Kazumi; Suzuki, Atsushi; Akiyama, Tsuyoshi; Tokumitsu, Katsuhisa; Yamada, Masahiro; Nakamura, Mika.

Japanese Journal of Applied Physics 52 04CR07(1) - 04CR07(5) 2013.3

Microstructures and photovoltaic properties of C60 based solar cells with copper oxides, CuInS2, phthalocyanines, porphyrin, PVK, nanodiamond, germanium and exciton diffusion blocking layers Reviewed

Materials Technology 28 ( - ) 21 - 39 2013.3

Facile Solubilization and Photovoltaic Application of C60 Fullerene-Ethylenediamine Adduct Reviewed

Tsuyoshi Akiyama, Taiki Ueda, Yuji Ono, Kento Kimura, Ken-ichi Matsuoka, Sunao Yamada, and Takeo Oku

Chemistry Letters 42 ( 2 ) 177 - 179 2013.2

Preparation and Photovoltaic Application of Fullerene–Porphyrin Composite Micropowder（共著） Reviewed

Kimura, Kento; Oku, Takeo; Akiyama, Tsuyoshi*.

Chemistry Letters 42 694 - 696 2013.2

Effects of phosphorous doping to poly (methylphenyl silane) and fabrication of thin film solar cells Reviewed

Nakagawa J., Oku T., Suzuki A., Akiyama T., Tokumitsu K., Yamada M., Nakamura M.

Journal of Physics: Conference Series 433 ( 1 ) 2013.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Physics: Conference Series

Effects of phosphorus bromine (PBr ) doping to polysilane were investigated for spin-coating thin films. Phosphorus doped poly (methylphenyl silane) (PMPS) provided n-type semiconductor behavior, which was confirmed by Hall effect measurements. Desorption of phenyl and methyl groups in doped PMPS thin films was observed after annealing at 300 °C from Raman scattering measurements and theoretical calculations. The band gap energy of PMPS was measured to be 3.2 eV. Decrease of photoluminescence intensity of PMPS was observed by phosphorus doping. Microstructures of the doped PMPS thin films were investigated by using X-ray diffraction, which indicated doped PMPS had an amorphous structure after annealing. A solar cell with PMPS(PBr ):poly[3-hexylthiophene] bulk-heterojunction structure was fabricated, and provided a photovoltaic behavior. Formation mechanism and carrier transport mechanism of the doped PMPS thin films were proposed. 3 3

DOI： 10.1088/1742-6596/433/1/012026

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Fabrication of C<inf>60</inf> assembly films via an fullerene-amine addition reaction by using stepwise immersion Reviewed

Banya S., Matsumoto T., Oku T., Akiyama T.

Journal of Physics: Conference Series 433 ( 1 ) 2013.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Physics: Conference Series

Fullerene C thin films were successfully fabricated on the surface of amino-substituted substrates via a reaction between C and an NH group of 1,2-diaminoethane (DAE) using simple immersion processes. The maximum thicknesses of the fullerene assembled films increased with the number of immersions into the fullerene solution. Layered fullerenes were obtained by a series of repeated processes. The aggregated C thin films were evaluated using transmission absorption measurements, transmission electron microscopy, and atomic force microscopy. These analyses suggest the presence of C -DAE aggregates on the substrates. 60 60 2 60 60

DOI： 10.1088/1742-6596/433/1/012007

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Fabrication and characterization of silicon naphthalocyanine, gallium phthalocyanine and fullerene-based organic solar cells with inverted structures Reviewed

Oku T., Nose S., Yoshida K., Suzuki A., Akiyama T., Yamasaki Y.

Journal of Physics: Conference Series 433 ( 1 ) 2013.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Physics: Conference Series

Fullerene/phthalocyanine solar cells with inverted structures were fabricated, and the photovoltaic properties, optical absorption and microstructrues were investigated. Silicon naphthalocyanine, gallium phthalocyanine, and poly(3-hexylthiophene) were used for donor materials, and 6,6-phenyl C -butyric acid methyl ester was also used as an acceptor material. The solar cells with the inverted structure provided higher conversion efficiencies by addition of silicon naphthalocyanine, and had more stability compared to that with normal structure in the air. Nanostructures of the solar cells were investigated by transmission electron microscopy, which indicated the dispersion of nanocrystals in the active layers. Energy levels of the molecules were calculated, and a carrier transport mechanism was proposed. 61

DOI： 10.1088/1742-6596/433/1/012025

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Fabrication and characterization of polysilane: PCBM bulk heterojunction solar cells Reviewed

Yoshida K., Oku T., Suzuki A., Akiyama T., Tokumitsu K., Nakamura M., Yamada M.

Central European Journal of Engineering 3 ( 2 ) 165 - 169 2013.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Central European Journal of Engineering

Polysilane/fullerene bulk heterojunction solar cells were fabricated on indium tin oxide electrodes by a spin-coating method, and performance and microstructures of the solar cells were investigated. Decaphenylcyclopentasilane (PDPS), polymethlyphenylsilane (PMPS) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) were used for the solar cells. The conversion efficiencies of PDPS:PCBM solar cells were higher than those of PMPS:PCBM devises. Transmission electron microscopy and X-ray diffraction indicated that PDPS:PCBM layer had a nanocomposite structure.

DOI： 10.2478/s13531-012-0057-6

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Fabrication and characterization of polymer tandem solar cells Reviewed

Maruhashi H., Suzuki A., Akiyama T., Oku T.

Journal of Physics: Conference Series 433 ( 1 ) 2013.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Physics: Conference Series

Polymer tandem solar cells were fabricated and characterized. Copolymer poly(3-hexylthiophene-2,5-diyl) (P3HT) and poly((4,4-octyldithieno(3,2-b:20,30- d)silole)-2,6-diyl-alt-(2,1,3-benzothiadiazole)-4,7-diyl) (PSBTBT) were used as p-type semiconductors, and [6,6]-phenyl-C -butyric acid methyl ester (PCBM) was used as an n-type semiconductor. The open circuit voltage was improved up to 0.69 V by using the tandem structure of P3HT:PCBM and PSBTBT:PCBM layers as compared with those of P3HT:PCBM and PSBTBT:PCBM single cell of 0.53 V and 0.10 V, respectively. Absorption of the tandem cell was in the range of 400 to 800 nm, which corresponded to a sum of those in P3HT:PCBM and PSBTBT:PCBM single cells. 61

DOI： 10.1088/1742-6596/433/1/012023

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Fabrication and characterization of copper oxide-zinc oxide solar cells prepared by electrodeposition Reviewed

Fujimoto K., Oku T., Akiyama T., Suzuki A.

Journal of Physics: Conference Series 433 ( 1 ) 2013.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Physics: Conference Series

Copper oxide-based heterojunction solar cells were fabricated by electrodeposition, and the electronic and optical properties were investigated. ZnO was used as an n-type semiconductor, and copper oxides were used as p-type semiconductors. A photovoltaic device based on an FTO/ZnO/Cu O heterojunction structure provided short-circuit current density of 2.7 mAcm and open circuit voltage of 0.28 V under an air mass 1.5 illumination. Microstructures of the solar cells were investigated by scanning electron microscope and X-ray diffraction, which indicated formation of copper oxides and ZnO. Energy levels of the solar cells were discussed. 2 -2

DOI： 10.1088/1742-6596/433/1/012024

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Photochemical half-cells using mixture films of fullerene-ethylenediamine adduct microparticles and polythiophene Reviewed

Akiyama T., Matsumura S., Matsuoka K., Oku T., Yamada S.

Journal of Physics: Conference Series 433 ( 1 ) 2013.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Physics: Conference Series

In this study, C fullerene-ethylenediamine adduct microparticles were prepared. Mixture films of these microparticles and polythiophene were fabricated on indium-tin-oxide transparent electrodes by spin-coating. Incorporation of C -ethylenediamine microparticles was verified by scanning electron microscopy (SEM) measurements. The coverage values of these microparticles were approximately 3-17%, which were calculated from SEM images of modified electrodes. Fluorescence spectra of modified electrodes indicated that the emission intensity of polythiophene in these mixture films was apparently quenched by these C -ethylenediamine microparticles as compared with a polythiophene film without these microparticles. In the presence of methylviologen, these modified electrodes generated stable photocurrent. The photoexciting species was polythiophene, which was verified by profiles of photocurrent action spectra. The C -ethylenediamine microparticles substantially enhanced the photocurrent signals generated by the polythiophene-modified electrode. 60 60 60 60

DOI： 10.1088/1742-6596/433/1/012010

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Metal-Enhanced Fluorescence Platforms Based on Plasmonic Ordered Copper Arrays: Wavelength Dependence of Quenching and Enhancement Effects（共著） Reviewed

Sugawa, Kosuke*; Tamura, Takahiro; Tahara, Hironobu; Yamaguchi, Daisuke; Akiyama, Tsuyoshi; Otsuki, Joe; Kusaka, Yasuyuki; Fukuda, Nobuko; Ushijima, Hirobumi.

ACS Nano 7 9997 - 10010 2013.1

Fabrication and characterization of heterojunction solar cells of hexadecafluorophthalocyanine/metal phthalocyanine Reviewed

Suzuki A., Mizuno A., Oku T., Akiyama T., Yamasaki Y.

Proceedings of SPIE - The International Society for Optical Engineering 8409 2012.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Proceedings of SPIE - The International Society for Optical Engineering

Fluorophthlocyanine thin films were used as n-type semiconductor in organic solar cell. Heterojunction solar cells of cupper hexadecafluorophthalocyanine (F CuPc) / copper phthalocyanine (CuPc) and F CuPc / zinc phthalocyanine (ZnPc) deposited with PEDOT-PSS on ITO as electrode were fabricated and characterized. Comparison between CuPc and ZnPc as p-type semiconductor on photovoltaic performance was studied. Light-induced charge separation and charge transfer was investigated by current density and optical absorption. Internal microstructure in active layer was measured by transmission electron microscopy, X-ray and electron diffractions. The F CuPc thin film in the deposited active layer worked for electron-accepting layer as n-type semiconductor. The photovoltaic performance was original in charge transfer from CuPc to F CuPc in active layer. © 2012 SPIE. 16 16 16 16

DOI： 10.1117/12.921210

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Fabrication and Characterization of Bulk Heterojunction Solar Cells Based on Liquid-Crystal Semiconductive Polymer Reviewed

Atsushi Suzuki, Shinichi Ogahara, Tsuyoshi Akiyama, Takeo Oku

Energy and Power Engineering 4 ( - ) 459 - 464 2012.11

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Papers - AKIYAMA Tsuyoshi