Faculty Profiles - AKIYAMA Tsuyoshi

Papers - AKIYAMA Tsuyoshi

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Fabrication of dense two-dimensional assemblies over vast areas comprising gold(core)-silver(shell) nanoparticles and their surface-enhanced Raman scattering properties Reviewed

Sugawa K., Tanoue Y., Ube T., Yanagida S., Yamamuro T., Kusaka Y., Ushijima H., Akiyama T.

Photochemical and Photobiological Sciences 13 ( 1 ) 82 - 91 2014.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Photochemical and Photobiological Sciences

Fabrication of dense two-dimensional assemblies consisting of gold(core)-silver(shell) nanoparticles and the resulting peculiar surface-enhanced Raman scattering (SERS) activity are reported. The assemblies were prepared via assembly at air-toluene interfaces by drop-casting toluene solutions containing the nanoparticles protected with octadecylamine molecules onto glass plates. This simple process, which does not require special apparatus or significant fabrication time, leads to uniform assemblies over vast areas (∼34 cm ). In the SERS measurements, the high spatial reproducibility of the SERS signals from p-aminothiophenol adsorbed on the assemblies over vast areas demonstrates that this method is useful for the quantitative investigation of SERS mechanisms. Under 532 nm laser excitation, the difference in the enhancement factors of the SERS signals at the a mode between assemblies consisting of gold, silver, and core-shell nanoparticles can be explained by the degree of overlap of the excitation wavelength with their plasmon coupling modes. In contrast, under 785 nm excitation, even though the plasmon band of the core-shell nanoparticle assemblies does not significantly overlap with the excitation wavelength as compared with that of gold nanoparticle assemblies, the enhancement factor from the core-shell nanoparticle assemblies was stronger than those from the gold nanoparticle assemblies. Therefore, we have demonstrated that the gold(core)-silver(shell) nanoparticle assemblies are excellent SERS active materials, which have strong electromagnetic mechanism (EM) as well as chemical mechanism (CM) effects due to the silver shells. © 2014 The Royal Society of Chemistry and Owner Societies. 2 1

DOI： 10.1039/c3pp50281c

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Fabrication and characterization of TiO<inf>2</inf>/CH<inf>3</inf>NH <inf>3</inf>PbI<inf>3</inf>-based photovoltaic devices Reviewed

Zushi M., Suzuki A., Akiyama T., Oku T.

Chemistry Letters 43 ( 6 ) 916 - 918 2014.1

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

TiO /CH NH PbI -based photovoltaic devices were fabricated by a spin-coating method using a mixture solution. Photovoltaic properties of the solar cells were investigated by optical absorption, current densityvoltage characteristics, and incident photon to current conversion efficiency. Effects of TiO addition and hole-transport layers were also investigated. Microstructures of the cells were investigated by transmission electron microscopy, which indicated a nanoparticle structure of TiO , and atomic arrangements of Pb atoms in the CH NH PbI crystal were also directly observed. © 2014 The Chemical Society of Japan. 2 3 3 3 2 2 3 3 3

DOI： 10.1246/cl.140127

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Fabrication and characterization of PCBM:P3HT:silicon phthalocyanine bulk heterojunction solar cells with inverted structures Reviewed

Oku T., Hori S., Suzuki A., Akiyama T., Yamasaki Y.

Japanese Journal of Applied Physics 53 ( 5 SPEC. ISSUE 1 ) 2014.1

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

[6,6]-phenyl C -butyric acid methyl ester and poly(3-hexylthiophene) bulk heterojunction solar cells doped with silicon phthalocyanine (SiPc) were fabricated and characterized. The photovoltaic properties of the solar cells with an inverted structure were improved by the SiPc addition, which were investigated on the bases of current density-voltage characteristics, incident photon to current conversion efficiency, and internal quantum efficiency. The solar cell with the inverted structure also showed good stability in air compared with the normal stacking devices. The microstructure of the solar cells was investigated by X-ray diffraction and transmission electron microscopy, and the carrier separation and transfer of the solar cells were discussed. © 2014 The Japan Society of Applied Physics. 61

DOI： 10.7567/JJAP.53.05FJ08

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Microstructures, optical and photoelectric conversion properties of spherical silicon solar cells with anti-reflection SnO<inf>x</inf>:F thin films Reviewed

Oku T., Kanayama M., Ono Y., Akiyama T., Kanamori Y., Murozono M.

Japanese Journal of Applied Physics 53 ( 5 SPEC. ISSUE 1 ) 2014.1

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

The microstructures and optical and photoelectric conversion properties of spherical silicon (Si) solar cells were investigated and discussed. The surface of the spherical Si with a pn junction provided high crystallinity, and the lattice constant of the center of Si spheres is larger than that of the surface, which would be due to the lattice distortion by defect structures at the center of Si. The conversion efficiencies of spherical Si solar cells coated with SnO :F anti-reflection thin films were improved by annealing. The optical absorption and fluorescence of the solar cells increased, and the lattice constants of SnO :F anti-reflection layers decreased after annealing. The mechanisms of chemical reactions at the Si/metal interface were also discussed. © 2014 The Japan Society of Applied Physics. x x

DOI： 10.7567/JJAP.53.05FJ03

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Selective implantation of gold nanoparticles onto the surface on one side of a self-standing polymer film Reviewed

Akiyama T., Yoshida K., Yamada S.

RSC Advances 4 ( 107 ) 62375 - 62379 2014.1

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

A novel method of highly-selective implantation of gold nanoparticles onto one surface of a polymer thin film with sub-micrometer thickness is demonstrated. The poly(methyl methacrylate) (PMMA) film of about 270 nm thickness, where gold nanoparticles (AuNPs) of ∼20 nm diameter were exclusively implanted on one surface, was successfully fabricated. The preparation was carried out by using a water-organic interface at room temperature. The resultant film was self-standing in a loop of as large as about 3 cm diameter. AuNPs were located only at the surface on one side of the PMMA film, which is confirmed using transmission absorption spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy. After annealing the PMMA film incorporating AuNPs in hot water, only the surface on one side of the film, where AuNPs were located, became conductive.

DOI： 10.1039/c4ra09553g

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Photovoltaic properties and morphology of organic solar cells based on liquid-crystal semiconducting polymer with additive Reviewed

Suzuki A., Zushi M., Suzuki H., Ogahara S., Akiyama T., Oku T.

AIP Conference Proceedings 1585 164 - 170 2014.1

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

Bulk heterojunction organic solar cell based on liquid crystal semiconducting polymers of poly[9,9-dioctylfluorene-co-bithiophene] (F8T2) as p-type semiconductors and fullerenes (C ) and [6,6]-phenyl-C -butyric acid methyl ester (PCBM) as electron donor and acceptor has been fabricated and characterized for improving photovoltaic and optical properties. The photovoltaic performance including current voltage curves in the dark and illumination of the F8T2/C conventional and inverted bulk heterojunction solar cells were investigated. Relationship between the photovoltaic properties and morphological behavior was focused on tuning for optimization of photo-voltaic performance under annealing condition near glass transition temperature. Additive-effect of diiodooctane (DIO) and poly(3-hexylthiophene-2,5-diyl) (P3HT) on the photovoltaic performance and optical properties was investigated. Mechanism of the photovoltaic properties of the conventional and inverted solar cells will be discussed by the experimental results. 60 61 60

DOI： 10.1063/1.4866636

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Effects of phosphorus addition to poly-methyl-phenyl-silane based photovoltaic devices Reviewed

Oku T., Nakagawa J., Suzuki A., Akiyama T., Yamada M., Fukunishi S., Kohno K., Sasaki M.

Physica Status Solidi (C) Current Topics in Solid State Physics 10 ( 12 ) 1832 - 1835 2013.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Physica Status Solidi (C) Current Topics in Solid State Physics

Effects of phosphorus addition to poly-methyl-phenyl-silane (PMPS) were investigated for spin-coating thin films. Microstructures of the PMPS thin films were investigated by X-ray diffraction and atomic force microscopy. PMPS thin films doped with phosphorus (P) had an amorphous structure after annealing at 300 °C. Decrease of fluorescence intensity of PMPS was observed by phosphorus doping. 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. Solar cells with PMPS (P)/poly[3-hexylthiophene] bulk heterojunction and heterojunction structures were fabricated, and provided a photovoltaic behavior. Formation mechanism and carrier transport mechanism of the doped PMPS thin films were proposed. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DOI： 10.1002/pssc.201300368

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Microstructure analysis and properties of spherical silicon solar cells with anti-reflection thin films Reviewed

Oku T., Kanayama M., Akiyama T., Kanamori Y., Murozono M.

Physica Status Solidi (C) Current Topics in Solid State Physics 10 ( 12 ) 1840 - 1843 2013.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Physica Status Solidi (C) Current Topics in Solid State Physics

Structure and properties of spherical silicon solar cells with anti-reflection thin films were investigated and discussed. Conversion efficiencies of spherical Si solar cells coated with F-doped SnO anti-reflection films were improved by annealing. Optical absorption and fluorescence of the solar cells increased after annealing. Lattice constants of F-doped SnO anti-reflection layers, which were investigated by X-ray diffraction, decreased after annealing. Mechanisms of atomic diffusion in SnO and reactions at the Si/metal interface were discussed. The present work indicated a guideline for spherical silicon solar cells with higher efficiencies. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. 2 2 2

DOI： 10.1002/pssc.201300372

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Fabrication and characterization of PCBM: P3HT bulk heterojunction solar cells doped with silicon naphthalocyanine Reviewed

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

Physica Status Solidi (C) Current Topics in Solid State Physics 10 ( 12 ) 1836 - 1839 2013.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Physica Status Solidi (C) Current Topics in Solid State Physics

[6,6]-phenyl C -butyric acid methyl ester: poly(3-hexylthiophene) bulk heterojunction solar cells doped with silicon naphthalocyanine were fabricated and characterized. Photovoltaic properties of the solar cells with inverted structures were investigated by optical absorption, current density-voltage characteristic, incident photon to current conversion efficiency, and internal quantum efficiency. The silicon naphthalocyanine blended as the third component absorbed near-infrared light. Microstructure of the solar cells was investigated by X-ray diffraction, and energy levels of the solar cells were discussed. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. 61

DOI： 10.1002/pssc.201300369

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Mixing effect of gold and silver nanoparticles on enhancement in performance of organic thin-film solar cells Reviewed

Akiyama T., Yamamoto T., Oku T., Yahiro M., Kurihara T., Adachi C., Yamada S.

Japanese Journal of Applied Physics 52 ( 12 ) 2013.12

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

Bulk-heterojunction organic thin-film solar cells incorporating gold and silver nanoparticles were fabricated and evaluated. These nanoparticles were embedded in the hole-transport layer of the solar cells. Plasmonic absorption peaks of isolated gold and silver nanoparticles were confirmed from extinction spectra even in the hole-transport material. The incorporation of gold and silver nanoparticles increased the photoelectric conversion efficiency of organic thin-film solar cells, whose enhancement ratio was further increased by mixing gold and silver nanoparticles. © 2013 The Japan Society of Applied Physics.

DOI： 10.7567/JJAP.52.122301

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Effects of phosphorus addition to poly-methyl-phenyl-silane based photovoltaic devices（共著） Reviewed

Oku, Takeo*; Nakagawa, Junya; Suzuki, Atsushi; Akiyama, Tsuyoshi; Yamada, Masahiro; Fukunishi, Sakiko; Kohno, Kazufumi; Sasaki, Muneo.

physica status solidi (c) 10 1832 - 1835 2013.12

Microstructure analysis and properties of spherical silicon solar cells with anti-reflection thin films（共著） Reviewed

Oku, Takeo*; Kanayama, Masato; Akiyama, Tsuyoshi; Kanamori, Yoichi; Murozono, Mikio.

physica status solidi (c) 10 1840 - 1843 2013.12

Fabrication and characterization of PCBM:P3HT bulk heterojunction solar cells doped with silicon naphthalocyanine（共著） Reviewed

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

physica status solidi (c) 10 1836 - 1839 2013.12

Effects of phosphorus addition to poly-methyl-phenyl-silane based photovoltaic devices（共著） Reviewed

Oku, Takeo*; Nakagawa, Junya; Suzuki, Atsushi; Akiyama, Tsuyoshi; Yamada, Masahiro; Fukunishi, Sakiko; Kohno, Kazufumi; Sasaki, Muneo.

physica status solidi (c) 10 1832 - 1835 2013.12

Microstructure analysis and properties of spherical silicon solar cells with anti-reflection thin films（共著） Reviewed

Oku, Takeo*; Kanayama, Masato; Akiyama, Tsuyoshi; Kanamori, Yoichi; Murozono, Mikio.

physica status solidi (c) 10 1840 - 1843 2013.12

Fabrication and characterization of PCBM:P3HT bulk heterojunction solar cells doped with silicon naphthalocyanine（共著） Reviewed

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

physica status solidi (c) 10 1836 - 1839 2013.12

Metal-enhanced fluorescence platforms based on plasmonic ordered copper arrays: Wavelength dependence of quenching and enhancement effects Reviewed

Sugawa K., Tamura T., Tahara H., Yamaguchi D., Akiyama T., Otsuki J., Kusaka Y., Fukuda N., Ushijima H.

ACS Nano 7 ( 11 ) 9997 - 10010 2013.11

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

Ordered arrays of copper nanostructures were fabricated and modified with porphyrin molecules in order to evaluate fluorescence enhancement due to the localized surface plasmon resonance. The nanostructures were prepared by thermally depositing copper on the upper hemispheres of two-dimensional silica colloidal crystals. The wavelength at which the surface plasmon resonance of the nanostructures was generated was tuned to a longer wavelength than the interband transition region of copper (>590 nm) by controlling the diameter of the underlying silica particles. Immobilization of porphyrin monolayers onto the nanostructures was achieved via self-assembly of 16-mercaptohexadecanoic acid, which also suppressed the oxidation of the copper surface. The maximum fluorescence enhancement of porphyrin by a factor of 89.2 was achieved as compared with that on a planar Cu plate (CuP) due to the generation of the surface plasmon resonance. Furthermore, it was found that while the fluorescence from the porphyrin was quenched within the interband transition region, it was efficiently enhanced at longer wavelengths. It was demonstrated that the enhancement induced by the proximity of the fluorophore to the nanostructures was enough to overcome the highly efficient quenching effects of the metal. From these results, it is speculated that the surface plasmon resonance of copper has tremendous potential for practical use as high functional plasmonic sensor and devices. © 2013 American Chemical Society.

DOI： 10.1021/nn403925d

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Mixing Effect of Gold and Silver Nanoparticles on Enhancement in Performance of Organic Thin-Film Solar Cells（共著） Reviewed

Akiyama, Tsuyoshi*; Yamamoto, Tomoki; Oku, Takeo; Yahiro, Masayuki; Kurihara, Takashi; Adachi, Chihaya; Yamada, Sunao.

Japanese Journal of Applied Physics 52 1222301(1) - 1222301(4) 2013.11

Densely arranged two-dimensional silver nanoparticle assemblies with optical uniformity over vast areas as excellent surface-enhanced Raman scattering substrates Reviewed

Tanoue Y., Sugawa K., Yamamuro T., Akiyama T.

Physical Chemistry Chemical Physics 15 ( 38 ) 15802 - 15805 2013.10

Language：English Publishing type：Research paper (scientific journal) Publisher：Physical Chemistry Chemical Physics

Dense two-dimensional assemblies of silver nanoparticles were fabricated over vast areas (∼19 cm ) by utilizing a simple liquid-liquid interface assembly technique. The Raman signal for p-aminothiophenol immobilized on the assemblies was drastically enhanced by plasmon coupling-induced hot spots, and the enhanced signal showed high spatial reproducibility. © 2013 the Owner Societies. 2

DOI： 10.1039/c3cp52400k

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Fabrication and characterization of fullerene-based solar cells containing phthalocyanine and naphthalocyanine dimers（共著） Reviewed

Takeda, Akihiro; Oku, Takeo*; Suzuki, Atsushi, Akiyama, Tsuyoshi; Yamasaki, Yasuhiro.

Synthetic Metals 177 48 - 51 2013.8

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Papers - AKIYAMA Tsuyoshi