Papers - IKEDA Shigeru
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Thin film solar cell based on CuSbS2 absorber fabricated from an electrochemically deposited metal stack Reviewed
Wilman Septina, Shigeru Ikeda, Yuta Iga, Takashi Harada, Michio Matsumura
THIN SOLID FILMS 550 700 - 704 2014.1
Joint Work
Authorship:Lead author Publisher:ELSEVIER SCIENCE SA
Copper antimony sulfide (CuSbS2) thin films were fabricated by sulfurization of an electrodeposited metallic stack composed of Cu and Sb on a Mo-coated glass (Mo/glass) substrate. A CuSbS2 film containing appreciable impurity components was obtained when the precursor metallic stack was heated monotonically from room temperature to 450 degrees C in Ar followed by sulfurization. The film also showed poor adherence due to a large number of crevices; there were many appreciable pinholes over the entire surface of the film. On the other hand, a CuSbS2 film without any impurity phases was obtained when the metallic precursor film was pretreated at 510 degrees C in Ar for 60 min just before sulfurization at 450 degrees C. It was also observed that the thus-obtained CuSbS2 film showed good adhesion to the Mo/glass substrate and almost no notable pinholes. As expected from structural analyses, the 510 degrees C-pretreated film worked as a relatively efficient absorber for the thin film solar cell with an Al:ZnO/CdS/CuSbS2/Mo/glass structure: it gave preliminary conversion efficiency of 3.1%. (C) 2013 Elsevier B.V. All rights reserved.
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Mechanistic aspects of preheating effects of electrodeposited metallic precursors on structural and photovoltaic properties of Cu(2)Zn(5)nS(4) thin films Reviewed
Yixin Lin, Shigeru Ikeda, Wilman Septina, Yoshihito Kawasaki, Takashi Harada, Michio Matsumura
SOLAR ENERGY MATERIALS AND SOLAR CELLS 120 218 - 225 2014.1
Joint Work
Authorship:Lead author Publisher:ELSEVIER SCIENCE BV
Effects of 350 degrees C preheating of electrochemically stacked Cu-Sn-Zn layers in an inert atmosphere on structural and morphological properties of quaternary kesterite Cu2ZnSnS4 (CZTS) films obtained by sulfurization of the metallic layers were investigated. When the CZTS film was fabricated without the 350 degrees C preheating, the film contained a secondary Cu2SnS3 phase and other impurities. The CZTS film also showed poor adhesion to the bottom molybdenum (Mo) substrate with many crevices and voids in the film; a very thick MoS2 layer was formed at the top part of the Mo layer. These structural failures of the CZTS film were significantly reduced when the metallic precursor was preheated at 350 degrees C before sulfurization for 20 min: the CZTS film thus-obtained exhibited no secondary phases, good adhesion to the bottom Mo layer, flat and densely packed surface morphology, no appreciable crevices or voids, and formation of a relatively thin MoS2 layer. Based on results of studies on structural transformations during 350 degrees C preheating and successive sulfurization, such differences in properties of resulting CZTS films are attributed to differences in formation pathways. Moreover, since 350 degrees C preheating for a longer duration was found to be detrimental for the properties of resulting CZTS films, there should be an optimum duration of preheating to achieve a good CZTS film for solar cell application. As expected from these properties, the solar cell with an Al:ZnO/CdS/CZTS/Mo structure derived from the metallic precursor preheated at 350 degrees C for 20 min showed the best conversion efficiency of 5.6%. (C) 2013 Elsevier B.V. All rights reserved.
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Fabrication of Cu2ZnSnSe4 thin films from an electrodeposited Cu-Zn-Sn-Se/Cu-Sn-Se bilayer Reviewed
Wilman Septina, Shigeru Ikeda, Takashi Harada, Michio Matsumura
PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 10, NO 7-8 10 ( 7-8 ) 1062 - 1066 2013.8
Joint Work
Authorship:Lead author Publisher:WILEY-V C H VERLAG GMBH
In this study, a novel sequential electrodeposition of Cu-Zn-Sn-Se and Cu-Sn-Se layers was applied for fabrication of a Cu2ZnSnSe4 (CZTSe) thin film. The desired Cu-Zn-Sn-Se/Cu-Sn-Se bilayer was obtained at a selected applied potential from electrolytes containing corresponding metal and selenium ions. Annealing of the bilayer film under argon (Ar) flow induced significant losses of Sn and Se components due probably to evaporation of the SnSe compound. Suppression of these losses could be realized by introduction of Se vapor during the annealing: as a result, a CZTSe thin film with an ideal Cu-poor/Zn-rich composition for solar cell application was obtained. The solar cell with a device with the structure of glass/Mo/CZTSe/CdS/ZnO/AZO derived from thus-obtained CZTSe film exhibited a conversion efficiency of 1.1%, while the device still possessed a significant leakage current and a high series resistance. (C) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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Synthesis of Nickel Nanoparticles Encapsulated in a Hollow Silica Shell Reviewed
Takashi Harada, Takuji Misaka, Takao Sakata, Shigeru Ikeda, Michio Matsumura
ADVANCED MATERIALS DESIGN AND MECHANICS II 372 132 - 135 2013.8
Joint Work
Authorship:Lead author Publisher:TRANS TECH PUBLICATIONS LTD
A core-hollow shell composite composed of a nickel (Ni) nanoparticle core encapsulated in a hollow silica shell (Ni@SiO2) was prepared by using a nanocrystalline salt of nickel tris-hydrazine complex, which acted as not only a nickel source but also a solid template to produce the core-hollow shell structure. Structural characterizations using TEM and N-2 adsorption-desorption measurements of the thus-obtained Ni@SiO2 powder revealed that it was composed of a Ni nanoparticle core of ca. 4.0 nm in diameter and a rectangular-shaped hollow silica shell with a micropore (ca. 0.5 nm in diameter) system.
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The Effect of Annealing Temperature and KCN Etching on the Photovoltaic Properties of Cu(In,Ga)(S,Se)(2) Solar Cells Using Nanoparticles Reviewed
Duy-Cuong Nguyen, Ken Fukatsu, Keiji Tanimoto, Shigeru Ikeda, Michio Matsumura, Seigo Ito
INTERNATIONAL JOURNAL OF PHOTOENERGY 2013 416245-1 - 416245-7 2013.5
Joint Work
Publisher:HINDAWI PUBLISHING CORPORATION
Cu(In,Ga)S-2 nanoparticles were synthesized by a hot-injection method under a low-vacuum ambience, which were printed and annealed with Se vapor for Cu(In,Ga)(S,Se)(2) solar cells. The Cu(In,Ga)S-2 nanoparticles were around 14 nm, and the stable ink was obtained by dispersing the nanoparticles in hexanethiol. The crystallinity of the Cu(In,Ga)(S,Se)(2) films increased with the increase in annealing temperature. Cu(In,Ga)(S,Se)(2) solar cells with KCN etching after annealing showed better photovoltaic properties than KCN etching before annealing and without etching. The best cell was observed at an annealing temperature of 540 degrees C and KCN etching after annealing; the parameters of this cell were a short-circuit photocurrent density of 27.12 mA/cm(2), open-circuit voltage of 0.42V, fill factor of 0.38, and conversion efficiency of 4.3%.
DOI: 10.1155/2013/416245
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Fabrication of Pores in a Silicon Carbide Wafer by Electrochemical Etching with a Glassy-Carbon Needle Electrode Reviewed
Tomohiko Sugita, Kazuki Hiramatsu, Shigeru Ikeda, Michio Matsumura
ACS APPLIED MATERIALS & INTERFACES 5 ( 7 ) 2580 - 2584 2013.4
Joint Work
Publisher:AMER CHEMICAL SOC
An electrochemical method for making pores in a silicon carbide (SiC) wafer, in which a glassy-carbon (GC) needle electrode was used for processing, is described. By bringing the GC electrode into contact with SiC at its tip end in 20 mol dm(-3) HF solution and applying an anodic potential of or higher than 4 V vs Ag/AgCl to it, SiC was etched at the SiC/GC contact area, leading to pore formation in SiC. The diameter of the pore was almost the same as the diameter of the tip of the GC electrode (about 130 mu m). By addition of sulfuric acid to the HF solution, the rate of pore formation was increased. As a result, the depth of pores formed after processing for 5 h at 10 V vs Ag/AgCl was increased from 15.3 mu m to about 33 mu m by addition of sulfuric acid at a concentration of 3.0 mol dm(-3).
DOI: 10.1021/am303167c
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Pore Formation in a p-Type Silicon Wafer Using a Platinum Needle Electrode with Application of Square-Wave Potential Pulses in HF Solution Reviewed
Tomohiko Sugita, Kazuki Hiramatsu, Shigeru Ikeda, Michio Matsumura
ACS APPLIED MATERIALS & INTERFACES 5 ( 4 ) 1262 - 1268 2013.2
Joint Work
Publisher:AMER CHEMICAL SOC
By bringing an anodically biased needle electrode into contact with n-type Si at its tip in a solution containing hydrofluoric acid, Si is etched at the interface with the needle electrode and a pore is formed. However, in the case of p-type Si, although pores can be formed, Si is likely to be corroded and covered with a microporous Si layer. This is due to injection of holes from the needle electrode into the bulk of p-type Si, which shifts its potential to a level more positive than the potential needed for corrosion and formation of a microporous Si layer. However, by applying square-wave potential pulses to a Pt needle electrode, these undesirable changes are prevented because holes injected into the bulk of Si during the period of anodic potential are annihilated with electrons injected into Si during the period of cathodic potential. Even under such conditions, holes supplied to the place near the Si/metal interface are used for etching p-type Si, leading to formation of a pore at the place where the Pt needle electrode was in contact.
DOI: 10.1021/am302314y
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Single-step electrodeposition of a microcrystalline Cu2ZnSnSe4 thin film with a kesterite structure Reviewed
Wilman Septina, Shigeru Ikeda, Akio Kyoraiseki, Takashi Harada, Michio Matsumura
ELECTROCHIMICA ACTA 88 436 - 442 2013.1
Joint Work
Authorship:Lead author Publisher:PERGAMON-ELSEVIER SCIENCE LTD
Single-step electrodeposition synthesis of a Cu2ZnSnSe4 (CZTSe) film on a Mo-coated glass substrate from an acidic electrolyte containing Cu(II), Zn(II), Sn(IV), and Se(IV) species was investigated. The desired CZTSe film as the main phase was obtained at some selected applied potential ranges through reaction among binary selenides, Cu2Se, ZnSe and SnSe2, which were continuously formed in the present electrolyte containing all of the elements. Sulfurization of the as-deposited film at several temperatures under H2S gas flow resulted in the formation of corresponding mixed compounds of CZTSe and Cu2ZnSnS4 (CZTS), i.e., Cu2ZnSn(S,Se)(4) (CZTSSe): specifically, sulfurization at temperatures higher than 500 degrees C resulted in the formation of single-phase CZTSSe with S-rich compositions. By analyzing linear sweep voltammograms (LSVs) of sulfurized films under chopped irradiation, the films were confirmed to have p-type photoresponses; the film obtained by 500 degrees C sulfurization showed the largest photoresponse because of its sufficiently large grain size and less voids, whereas the presence of an anodic spike in the LSV curve as well as the observation of a broad external quantum efficiency (EQE) spectrum suggested the requirement of further improvement in film quality for photovoltaic application. (c) 2012 Elsevier Ltd. All rights reserved.
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Fabrication of CuInS2 and Cu(In, Ga) S-2 thin films by a facile spray pyrolysis and their photovoltaic and photoelectrochemical properties Reviewed
Shigeru Ikeda, Midori Nonogaki, Wilman Septina, Gunawan Gunawan, Takashi Harada, Michio Matsumura
CATALYSIS SCIENCE & TECHNOLOGY 3 ( 7 ) 1849 - 1854 2013.1
Joint Work
Authorship:Lead author Publisher:ROYAL SOC CHEMISTRY
Polycrystalline CuInS2 chalcopyrite thin films were formed on a Mo-coated glass substrate by annealing of spray deposited precursor films in a sulfur atmosphere. Structural and photoelectrochemical analyses of CuInS2 films obtained by annealing at 500 degrees C and 600 degrees C revealed that a well-defined crystalline film was obtained by the 600 degrees C annealing. Owing to these favorable properties, the solar cell with an Al: ZnO/CdS/CIS/Mo/glass structure based on the 600 degrees C annealed CuInS2 film showed higher conversion efficiency than that obtained on the cell derived from the 500 degrees C annealed CuInS2. Partial incorporation of Ga in the CuInS2 film with a Ga/In ratio of ca. 0.2 to form a Cu(In, Ga) S-2 mixed crystal without any reduction of photoelectrochemical properties can be achieved by introduction of a Ga source in the sprayed solution. As a result, the solar cell based on the 600 degrees C annealed Cu(In, Ga) S-2 film showed the best conversion efficiency (5.8%) of the present sprayed chalcopyrite films. By introduction of a CdS thin layer followed by loading Pt deposits, moreover, the 600 degrees C annealed Cu(In, Ga) S-2 film worked as a photocathode for photoelectrochemical water splitting with applied bias potential of 40.65 V.
DOI: 10.1039/c3cy00020f
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An inorganic/organic hybrid solar cell consisting of Cu2O and a fullerene derivative Reviewed
M. Alam Khan, Wilman Septina, Shigeru Ikeda, Michio Matsumura
THIN SOLID FILMS 526 191 - 194 2012.12
Joint Work
Publisher:ELSEVIER SCIENCE SA
We fabricated inorganic/organic hybrid solar cells consisting of a p-type Cu2O layer and a fullerene derivative (PCBM) layer, which were prepared by wet processes. The Cu2O layer was grown by electrochemical deposition from an alkaline solution (pH 12.5) containing copper (II) sulfate and lactic acid. A PCBM layer was deposited on it by spin-casting a solution of PCBM. The optimized solar cell showed short circuit current density of 1.5 mA/cm(2), open circuit voltage of 0.4 V, and overall power conversion efficiency of 0.095% under the condition of AM 1.5 G (100 mW/cm(2)). Improvement in mobility and lifetime of electrons in the Cu2O layer is considered to be the key to increase efficiency further. (c) 2012 Elsevier B.V. All rights reserved.
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A perspective on fabricating carbon-based nanomaterials by photocatalysis and their applications Reviewed
Yun Hau Ng, Shigeru Ikeda, Michio Matsumura, Rose Amal
ENERGY & ENVIRONMENTAL SCIENCE 5 ( 11 ) 9307 - 9318 2012.11
Joint Work
Authorship:Lead author Publisher:ROYAL SOC CHEMISTRY
Combining semiconductor photocatalysts with carbon nanostructures has been extensively investigated due to their enhanced photochemical conversion activity. While many nanocomposite synthesis methods have been reported, the emerging use of photocatalytic reactions in synthesizing these carbon-based semiconductor composites and even pure carbon nanomaterials is increasingly capturing the attention of the research community. Being categorized under photocatalysis, these carbon-based nanomaterials are designed by either utilizing the conduction band electron or valence band hole of a photocatalyst. This perspective surveys the literature, discusses the principle of the method and highlights the recent progress in the development of this synthetic method. Ongoing challenges and new possible solutions encountered in this research area are outlined.
DOI: 10.1039/c2ee22128d
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Cu2ZnSn(S,Se)(4) Thin Film Prepared from a Single-step Electrodeposited Cu-Zn-Sn-Se Precursor
Wilman Septina, Shigeru Ikeda, Akio Kyoraiseki, Takashi Harada, Michio Matsumura
2012 38TH IEEE PHOTOVOLTAIC SPECIALISTS CONFERENCE (PVSC) 2702 - 2706 2012.10
Joint Work
Authorship:Lead author Publisher:IEEE
Cu2ZnSn(S,Se)(4) thin film has been fabricated by sulfurization of a novel single-step electrodeposited Cu-Zn-Sn-Se precursor. Based on EDX analysis of the precursor film, the atomic percentages of Cu, Zn, Sn and Se measured to be 38.48%, 11.53%, 13.62% and 36.37%, respectively. The A1 Raman mode of Cu2ZnSnSe4 was detected from the film which suggests the formation of the quaternary compound during the deposition. Annealing of the precursor film at 550 degrees C under H2S-gas flow resulted in the formation of crystalline Cu2ZnSn(S,Se)(4) compound. Photoelectrochemical measurement of the film revealed that the Cu2ZnSn(S,Se)(4) thus-obtained had a p-type semiconductor photoresponse with the band gap energy of 1.48 eV.
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Homogeneous electrochemical deposition of in on a Cu-covered Mo substrate for fabrication of efficient solar cells with a CuInS2 photoabsorber Reviewed
Sun Min Lee, Shigeru Ikeda, Yasunari Otsuka, Wilman Septina, Takashi Harada, Michio Matsumura
ELECTROCHIMICA ACTA 79 189 - 196 2012.9
Joint Work
Authorship:Lead author Publisher:PERGAMON-ELSEVIER SCIENCE LTD
Electrochemical deposition of indium (In) on a copper-covered molybdenum-coated glass substrate from several acidic InCl3 solutions was studied for fabrication of CuInS2-based solar cells. When In was deposited using a simple acidic InCl3 solution at -0.80 V (vs. Ag/AgCl), island-shaped growth was observed, whereas a homogeneous In film was obtained from InCl3 solution containing citric acid and sodium citrate at -0.98 V (vs. Ag/AgCl). Electrochemical and structural analyses revealed that the citric acid additive had a function for smoothing the surface of the In deposit. The mixing with sodium citrate induced appreciable inhibition of H-2 evolution during the In deposition, leading to high current efficiency of >90%. The CuInS2 film derived from the homogeneous In had a uniform thickness with a smooth surface, while the CuInS2 film obtained from the island-shaped In deposit showed a large variation in thickness with recessed areas. The CuInS2 film derived from the homogeneous In was showed better photoelectrochemical response than that of the film fabricated from the island-shaped In. As expected from these differences, the solar cell with an Al:ZnO/CdS/CuInS2/Mo structure derived from the homogeneous In film showed the best conversion efficiency of 7.8% with relatively high reproducibility. (C) 2012 Elsevier Ltd. All rights reserved.
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Isotope tracing study on oxidation of water on photoirradiated TiO2 particles Reviewed
Thuan Duc Bui, En Yagi, Takashi Harada, Shigeru Ikeda, Michio Matsurnura
APPLIED CATALYSIS B-ENVIRONMENTAL 126 86 - 89 2012.9
Joint Work
Publisher:ELSEVIER SCIENCE BV
Water is oxidized to molecular oxygen on a TiO2 photocatalyst using electron acceptors such as Ag+ and Fe3+ ions. However, there has been no information about whether this reaction occurs or not using molecular oxygen as the electron acceptor. We found by analysis of oxygen in the gas phase using O-18-enriched water that this reaction does in fact occur. The quantum efficiency was higher with rutile-form particles than with anatase-form particles. O-2 was photocatalytically produced using O atoms supplied solely from water even in the presence of O-2 in the system. These results are important for deepening the understanding of TiO2 photocatalysts because molecular oxygen is used most frequently as the electron acceptor and the intermediates of oxidation of water are involved in various kinds of photocatalytic reactions. (c) 2012 Elsevier B.V. All rights reserved.
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Structural regulation of electrochemically deposited copper layers for fabrication of thin film solar cells with a CuInS2 photoabsorber Reviewed
Sun Min Lee, Shigeru Ikeda, Yasunari Otsuka, Takashi Harada, Michio Matsumura
JOURNAL OF NON-CRYSTALLINE SOLIDS 358 ( 17 ) 2424 - 2427 2012.9
Joint Work
Authorship:Lead author Publisher:ELSEVIER SCIENCE BV
Electrodeposition of Cu layers on a Mo-coated glass (Mo/glass) substrate from CuSO4 solutions containing citric acid and sodium citrate was studied for fabrication of CuInS2-based solar cells. When the deposition was performed using the CuSO4 solution containing citric acid, a Cu layer consisting of less-compact roundish grains with a rugged surface morphology was obtained. On the other hand, a compact Cu layer composed of large angular grains was formed from the CuSO4 solution containing sodium citrate. Electrochemical studies revealed that both organic additives worked as complexing agents to reduce the concentration of free Cu2+ ions. but complexation abilities of these additives were different, leading to the structural difference in the resulting Cu layers. The CuInS2 film derived from the former less-compact Cu layer had good adhesion between the CuInS2 film and Mo/glass, whereas the CuInS2 film obtained from the latter compact Cu layer was partially exfoliated because of large volume expansion stresses during the transformation of Cu and In stacked layers into the CuInS2 film. As expected from these differences, the solar cell with an Al:ZnO/CdS/CuInS2/Mo/glass structure derived from the former less-compact Cu layer showed better properties than those of the solar cell derived from the latter compact Cu layer. (C) 2011 Elsevier B.V. All rights reserved.
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Two routes for mineralizing benzene by TiO2-photocatalyzed reaction Reviewed
Thuan Duc Bui, Akira Kimura, Suguru Higashida, Shigeru Ikeda, Michio Mafsurnura
APPLIED CATALYSIS B-ENVIRONMENTAL 107 ( 43102 ) 119 - 127 2011.8
Joint Work
Publisher:ELSEVIER SCIENCE BV
When benzene was oxidized on TiO2-photocatalysts, muconaldehyde as well as phenol was identified as a product. Muconaldehyde was not produced from phenol, indicating that muconaldehyde and phenol are produced as initial stable intermediates by independent pathways. The amount of muconaldehyde produced in the reaction solution was low because it was rapidly oxidized on the photocatalyst. The contributions of the two pathways to the mineralization of benzene were analyzed by isotopic tracing methods using labeled benzene ((C6H6)-C-13) and labeled phenol ((C6H5OH)-C-13). The results showed that a larger part (60-70%) of benzene is initially converted to muconaldehyde. The percentage was dependent on the properties of TiO2 powders. It was also found that anatase-form powders show higher activity for oxidation of benzene than rutile powders do, whereas rutile-form powders show higher activity for oxidation of phenol than anatase powders do. (C) 2011 Elsevier B.V. All rights reserved.
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Plasmon-Enhanced Photocatalytic Activity of Cadmium Sulfide Nanoparticle Immobilized on Silica-Coated Gold Particles Reviewed
Tsukasa Torimoto, Hiroki Horibe, Tatsuya Kameyama, Ken-ichi Okazaki, Shigeru Ikeda, Michio Matsumura, Akira Ishikawa, Hajime Ishihara
JOURNAL OF PHYSICAL CHEMISTRY LETTERS 2 ( 16 ) 2057 - 2062 2011.8
Joint Work
Publisher:AMER CHEMICAL SOC
Nanocomposite photocatalysts of CdS nanoparticles immobilized on Au core-SiO2 shell particles, in which the SiO2 layer acts as an insulator layer to prevent direct electron transfer from photoexcited CdS to Au particles, were prepared. The photocatalytic activity of CdS particles for H-2 evolution was greatly dependent on the distance between CdS and Au particles, due to the locally enhanced electric field produced by photoexcitation of the localized surface plasmon resonance (LSPR) peak of Au particles. Increase in Au core size enlarged the optimal distance between Au and CdS for the enhancement of photocatalysis. This behavior was theoretically reproduced by solving a self-consistent equation system, in which the range of energy dissipation became wider for larger diameter of the Au sphere, and then the balance with the enhancement of photoexcitation of CdS particles by the LSPR-induced electric field was changed.
DOI: 10.1021/jz2009049
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Formation of Through-Holes in Si Wafers by Using Anodically Polarized Needle Electrodes in HF Solution Reviewed
Tomohiko Sugita, Chia-Lung Lee, Shigeru Ikeda, Michio Matsumura
ACS APPLIED MATERIALS & INTERFACES 3 ( 7 ) 2417 - 2424 2011.7
Joint Work
Publisher:AMER CHEMICAL SOC
Electrochemical pore formation in Si using an anodized needle electrode was studied. In the electrochemical process, a Pt, Ir or Pd needle with a diameter of 50-200 mu m was brought into contact at its tip with a Si wafer, which was not connected to an external circuit, in HF solution. By applying an anodic potential to the needle electrode against a Pt counter electrode, a pore with a diameter slightly larger than the diameter of the needle electrode was formed in both p-type and n-type Si, of which current efficiency was higher for n-type Si. Through-holes were electrochemically formed in p-type and n-type Si wafers at speeds higher than 30 mu m min(-1) using a sharpened Ir needle electrode. A model was proposed to explain the results, in which the pore formation was attributed to successive dissolution of Si atoms near the 3-phase (Si/metal/HF solution) boundary by positive holes injected from the needle electrode to the surface of Si.
DOI: 10.1021/am2003284
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A superstrate solar cell based on In-2(Se,S)(3) and CuIn(Se,S)(2) thin films fabricated by electrodeposition combined with annealing Reviewed
Shigeru Ikeda, Ryo Kamai, Sun Min Lee, Tetsuro Yagi, Takashi Harada, Michio Matsumura
SOLAR ENERGY MATERIALS AND SOLAR CELLS 95 ( 6 ) 1446 - 1451 2011.6
Joint Work
Authorship:Lead author Publisher:ELSEVIER SCIENCE BV
Stacked thin films composed of In-2(Se,S)(3) and CuIn(Se,S)(2) layers were grown on a fluorine-doped tin oxide (FTO)-coated glass substrate using electrodeposition of the corresponding selenide (In2Se3 and CuInSe2) precursors followed by annealing in H2S flow (5% in Ar). Structural characterizations of both layers revealed that the resulting film quality strongly depended on annealing conditions of both CuIn(Se,S)(2) and In-2(Se,S)(3) layers: a compact and uniform film was obtained by annealing both layers at 400 degrees C. Performance of Au/CuIn(Se,S)(2)/In-2(Se,S)(3)/FTO superstrate-type solar cells also followed these structural characteristics, i.e., a preliminary conversion efficiency of 2.9% was obtained on the device based on 400 degrees C-annealed In-2(Se,S)(3) and CuIn(Se,S)(2) layers. (C) 2010 Elsevier B.V. All rights reserved.
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Potentiostatic electrodeposition of cuprous oxide thin films for photovoltaic applications Reviewed
Wilman Septina, Shigeru Ikeda, M. Alam Khan, Takeshi Hirai, Takashi Harada, Michio Matsumura, Laurence M. Peter
ELECTROCHIMICA ACTA 56 ( 13 ) 4882 - 4888 2011.5
Joint Work
Authorship:Lead author Publisher:PERGAMON-ELSEVIER SCIENCE LTD
Potentiostatic deposition of Cu(2)O thin films on glass substrates coated with F-doped SnO(2) from an alkaline electrolyte solution (pH 12.5) containing copper (II) sulfate and lactic acid was studied for fabrication of a Cu(2)O/Al-doped ZnO (AZO) heterojunction solar cell. The band gap of the electrodeposited Cu(2)O films was determined by photoelectrochemical measurements to be around 1.9 eV irrespective of the applied potentials. The solar cells with a glass/FTO/Cu(2)O/AZO structure were fabricated by sputtering an AZO film onto the Cu(2)O film followed by deposition of an Al contact by vacuum evaporation. The highest efficiency of 0.603% was obtained with a Cu(2)O film deposited at -0.6V (vs. Ag/AgCl). This was attributed to better compactness and purity of the Cu(2)O film than those of the Cu(2)O films deposited at other potentials. (C) 2011 Elsevier Ltd. All rights reserved.