2024/10/07 更新

写真a

ゴトウ カズヒロ
後藤 和泰
GOTO Kazuhiro
所属
教育研究院 自然科学系 情報電子工学系列 准教授
自然科学研究科 電気情報工学専攻 准教授
工学部 工学科 准教授
職名
准教授
外部リンク

学位

  • 博士(工学) ( 2016年3月   東京工業大学 )

  • 修士(工学) ( 2013年3月   東京工業大学 )

  • 学士(理学) ( 2011年3月   東京理科大学 )

研究キーワード

  • ナノ構造

  • 表面・界面工学

  • 界面制御

  • 光電子材料

  • 太陽電池

研究分野

  • ナノテク・材料 / 複合材料、界面

  • ものづくり技術(機械・電気電子・化学工学) / 電気電子材料工学

  • ナノテク・材料 / 応用物性

経歴(researchmap)

  • 新潟大学   大学院自然科学研究科   准教授

    2023年4月 - 現在

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    国名:日本国

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  • 名古屋大学   大学院工学研究科   助教

    2017年12月 - 2023年3月

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  • 名古屋大学   大学院工学研究科   特任助教

    2016年4月 - 2017年11月

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経歴

  • 新潟大学   自然科学研究科 電気情報工学専攻   准教授

    2023年4月 - 現在

  • 新潟大学   工学部 工学科   准教授

    2023年4月 - 現在

  • 新潟大学   教育研究院 自然科学系 情報電子工学系列   准教授

    2023年4月 - 現在

学歴

  • 東京工業大学   大学院総合理工学研究科   物質科学創造専攻

    2013年4月 - 2016年3月

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    備考: 博士課程

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  • 東京工業大学   大学院総合理工学研究科   物質科学創造専攻

    2011年4月 - 2013年3月

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    備考: 修士課程

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  • 東京理科大学   理工学部   物理学科

    2007年4月 - 2011年3月

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所属学協会

委員歴

  • 35rd International Photovoltaic Science and Engineering Conference (PVSEC-35)   negotiation committee  

    2023年4月 - 現在   

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    団体区分:学協会

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  • 33rd International Photovoltaic Science and Engineering Conference (PVSEC-33)   Steering Committee  

    2021年4月 - 2023年3月   

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    団体区分:学協会

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  • International Conference on Solid State Devices and Materials   Program Committee  

    2021年4月 - 2023年3月   

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    団体区分:学協会

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論文

  • Hydrogenation of silicon-nanocrystals-embedded silicon oxide passivating contacts

    Masashi Matsumi, Kazuhiro Gotoh, Markus Wilde, Yasuyoshi Kurokawa, Katsuyuki Fukutani, Noritaka Usami

    Nanotechnology   2024年3月

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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.1088/1361-6528/ad115d

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  • Potential-induced degradation phenomena in single-encapsulation crystalline Si photovoltaic modules

    Yiming Qin, Asahi Yonemoto, Kazuhiro Gotoh, Atsushi Masuda

    Japanese Journal of Applied Physics   2024年2月

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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.35848/1347-4065/ad0414

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  • Core–shell yarn-structured triboelectric nanogenerator for harvesting both waterdrop and biomechanics energies

    Haitao Wang, Yasuyoshi Kurokawa, Jia-Han Zhang, Kazuhiro Gotoh, Xin Liu, Satoru Miyamoto, Noritaka Usami

    Applied Physics Express   2024年1月

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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.35848/1882-0786/ad1f06

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  • Improvement of passivation performance of silicon nanocrystal/silicon oxide compound layer by two-step hydrogen plasma treatment

    Masashi Matsumi, Kazuhiro Gotoh, Markus Wilde, Yasuyoshi Kurokawa, Katsuyuki Fukutani, Noritaka Usami

    Solar Energy Materials and Solar Cells   262   112538 - 112538   2023年10月

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    掲載種別:研究論文(学術雑誌)   出版者・発行元:Elsevier BV  

    DOI: 10.1016/j.solmat.2023.112538

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  • Impact of B2H6 plasma treatment on contact resistivity in silicon heterojunction solar cells

    Kazuhiro Gotoh, Ryo Ozaki, Motoo Morimura, Aki Tanaka, Yoshiko Iseki, Kyotaro Nakamura, Kazuo Muramatsu, Yasuyoshi Kurokawa, Yoshio Ohshita, Noritaka Usami

    Japanese Journal of Applied Physics   2023年8月

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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.35848/1347-4065/acc953

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  • Quantitative evaluation of implied open-circuit voltage after metal electrode deposition on TiO x /Si heterostructures by photoluminescence imaging: impact of metallization on passivation performance

    Shohei Fukaya, Kazuhiro Gotoh, Takuya Matsui, Hitoshi Sai, Yasuyoshi Kurokawa, Noritaka Usami

    Japanese Journal of Applied Physics   2023年8月

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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.35848/1347-4065/acc813

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  • Preparation and thermoelectric characterization of boron-doped Si nanocrystals/silicon oxide multilayers 査読

    K. Shibata, S. Kato, M. Kurosawa, K. Gotoh, S. Miyamoto, N. Usami, Y. Kurokawa

    Japanese Journal of Applied Physics   Vol. 62, No. SC, pp. SC1074-1〜8   2023年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.35848/1347-4065/acb779

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  • Performance enhancement of droplet-based electricity generator using a CYTOP intermediate layer

    Haitao Wang, Yasuyoshi Kurokawa, Kazuhiro Gotoh, Shinya Kato, Shigeru Yamada, Takashi Itoh, Noritaka Usami

    Japanese Journal of Applied Physics   62 ( SC )   SC1032 - SC1032   2023年1月

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    掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP Publishing  

    Abstract

    Effective strategies for improving the performance of a droplet-based electricity generator (DEG) remain a challenge. Herein, we propose to introduce an intermediate layer of cyclic transparent optical polymer (CYTOP) by adjusting the thickness, injecting ionized ions into the surface, and increasing the surface area. We observed the positive effects of the introduction of a CYTOP layer on outputs, especially with a greater thickness, surface ionized-air modification and larger surface area, which could promote the practical application of DEG in energy harvesting.

    DOI: 10.35848/1347-4065/acaca7

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    その他リンク: https://iopscience.iop.org/article/10.35848/1347-4065/acaca7/pdf

  • Influence of post-oxidizing treatment on passivation performance on the spin-coated titanium oxide films on crystalline silicon

    Hao Luo, Van Hoang Nguyen, Kazuhiro Gotoh, Saya Ajito, Tomohiko Hojo, Yasuyoshi Kurokawa, Eiji Akiyama, Noritaka Usami

    Thin Solid Films   764   139597 - 139597   2023年1月

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    掲載種別:研究論文(学術雑誌)   出版者・発行元:Elsevier BV  

    DOI: 10.1016/j.tsf.2022.139597

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  • Fabrication of BaSi2 homojunction diodes on Nb-doped TiO2 coated glass substrates by aluminum-induced crystallization and two-step evaporation method

    Yasuyoshi Kurokawa, Takamasa Yoshino, Kazuhiro Gotoh, Satoru Miyamoto, Noritaka Usami

    Japanese Journal of Applied Physics   2022年5月

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    掲載種別:研究論文(学術雑誌)   出版者・発行元:{IOP} Publishing  

    DOI: 10.35848/1347-4065/ac4077

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  • Improved conversion efficiency of p-type BaSi2/n-type crystalline Si heterojunction solar cells by a low growth rate deposition of BaSi2

    Michinobu Fujiwara, Kazuma Takahashi, Yoshihiko Nakagawa, Kazuhiro Gotoh, Takashi Itoh, Yasuyoshi Kurokawa, Noritaka Usami

    AIP Advances   12 ( 4 )   045115 - 045115   2022年4月

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    掲載種別:研究論文(学術雑誌)   出版者・発行元:{AIP} Publishing  

    DOI: 10.1063/5.0083812

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  • Zn1–xGexOy Passivating Interlayers for BaSi2 Thin-Film Solar Cells

    Yudai Yamashita, Kaori Takayanagi, Kazuhiro Gotoh, Kaoru Toko, Noritaka Usami, Takashi Suemasu

    ACS Applied Materials & Interfaces   14 ( 11 )   13828 - 13835   2022年3月

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    掲載種別:研究論文(学術雑誌)   出版者・発行元:American Chemical Society ({ACS})  

    DOI: 10.1021/acsami.1c23070

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  • Silicon Nanocrystals Embedded in Nanolayered Silicon Oxide for Crystalline Silicon Solar Cells

    Ryohei Tsubata, Kazuhiro Gotoh, Masashi Matsumi, Markus Wilde, Tetsuya Inoue, Yasuyoshi Kurokawa, Katsuyuki Fukutani, Noritaka Usami

    ACS APPLIED NANO MATERIALS   5 ( 2 )   2022年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER CHEMICAL SOC  

    This study describes the fabrication of silicon nanocrystals (Si NCs) in silicon oxide layers, which led to high-performance passivation and enhanced carrier transport in crystalline silicon (c-Si) solar cells. These Si NCs comprised nanocrystalline transport pathways in ultrathin dielectrics for reinforced passivating contact structures (NAnocrystalline Trans-port path in Ultrathin dielectrics for Reinforcing (NATURE) contacts). Si NCs were formed in silicon oxide layers by depositing hydrogenated amorphous silicon oxide (a-SiOx:H) with different oxygen concentrations, followed by postdeposition annealing (PDA). Based on microscopic images, the silicon oxide layer was maintained after PDA, and the Si NCs were formed in the silicon oxide matrix, leading to a relatively low recombination current (178.8 fA/cm(2)) compared with simple a-SiOx:H layer structures. Furthermore, the contact resistivity for the NATURE contact was 13.1 m omega center dot cm(2), which was comparable to that of a single a-SiOx:H layer with a low oxygen concentration. The developed NATURE contact structure expands the design flexibility scope for various functional devices containing a passivation contact layer. It allows for the production of c-Si solar cells with passivating contacts using thicker dielectric layers for improved reliability and long-term stability.

    DOI: 10.1021/acsanm.1c03355

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  • Impact of chemically grown silicon oxide interlayers on the hydrogen distribution at hydrogenated amorphous silicon/crystalline silicon heterointerfaces 査読

    K. Gotoh, M. Wilde, S. Ogura, Y. Kurokawa, K. Fukutani, N. Usami

    Applied Surface Science   567   150799   2021年11月

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    担当区分:筆頭著者, 責任著者   記述言語:英語   掲載種別:研究論文(学術雑誌)  

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  • Application of Bayesian optimization for high-performance TiO<inf>x</inf>/SiO<inf>y</inf>/c-Si passivating contact

    Shinsuke Miyagawa, Kazuhiro Gotoh, Kentaro Kutsukake, Yasuyoshi Kurokawa, Noritaka Usami

    Solar Energy Materials and Solar Cells   230   2021年9月

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    掲載種別:研究論文(学術雑誌)  

    We report on the application of Bayesian optimization (BO), which could accelerate the time-intensive process optimization of many parameters, to fabrication of the high-performance titanium oxide/silicon oxide/crystalline silicon passivating contact. The process contains pre-deposition treatment to form SiOy interlayer, atomic layer deposition (ALD) of TiOx, and hydrogen plasma treatment (HPT) as post-process. We attempted to optimize seven parameters for ALD and HPT by dealing with samples treated by three kinds of chemical solutions in the same batch. This permits to perform BO for each structure at the same time and determine the superior pre-deposition treatment. Consequently, carrier selectivity S10 estimated by independent measurements of the saturation current density and contact resistance was significantly improved by BO of only 12 cycles and 10 initial random experiments. These results certify that BO could efficiently provide experimental conditions in multidimensional parameter space although we need to consider the impact of the metallization process on the passivation performance.

    DOI: 10.1016/j.solmat.2021.111251

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  • Fabrication of heterojunction crystalline Si solar cells with BaSi2 thin films prepared by 2-step evaporation method 査読

    Y. Nakagawa, K. Takahashi, M. Fujiwara, K. O. Hara, K. Gotoh, Y. Kurokawa, T. Itoh, T. Suemasu, N. Usami

    Japanese Journal of Applied Physics   60   105503   2021年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:{IOP} Publishing  

    DOI: 10.35848/1347-4065/ac23ec

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  • Improved Performance of Titanium Oxide/Silicon Oxide Electron-Selective Contacts by Implementation of Magnesium Interlayers 査読

    Y. Nakagawa, K. Gotoh, T. Inoue, Y. Kurokawa, N. Usami

    Physica Status Solidi a   218   2100296   2021年8月

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    担当区分:責任著者   記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/pssa.202100296

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  • Fabrication of Silicon Nanowire Metal-Oxide-Semiconductor Capacitors with Al2O3/TiO2/Al2O3 Stacked Dielectric Films for the Application to Energy Storage Devices 査読

    R. Nezasa, K. Gotoh, S. Kato, S. Miyamoto, N. Usami, Y. Kurokawa

    Energies   14   4538   2021年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.3390/en14154538

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  • Realization of the Crystalline Silicon Solar Cell Using Nanocrystalline Transport Path in Ultra-thin Dielectrics for Reinforced Passivating Contact

    Ryohei Tsubata, Kazuhiro Gotoh, Tetsuya Inoue, Yasuyoshi Kurokawa, Noritaka Usami

    Conference Record of the IEEE Photovoltaic Specialists Conference   908 - 911   2021年6月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:Institute of Electrical and Electronics Engineers Inc.  

    We apply NAnocrystalline Transport path in Ultra-thin dielectrics for Reinforced passivating contact (NATURE contact) to crystalline silicon solar cells for simultaneous achievement of passivation and carrier extraction. The Si nanocrystals are formed in silicon oxide by deposition of hydrogenated amorphous silicon oxide with different oxygen concentration and subsequent annealing. NATURE contact with total layer thickness of 8 nm exhibits reasonably good passivation performance. Furthermore, we demonstrate that NATURE contact can be successfully implemented to the both sides of crystalline silicon solar cells. NATURE contact, which permits flexible structural and chemical design of a passivation contact layer, will open a possibility for various functional devices.

    DOI: 10.1109/PVSC43889.2021.9519096

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  • Passivation mechanism of the high-performance titanium oxide carrier-selective contacts on crystalline silicon studied by spectroscopic ellipsometry

    Kazuhiro Gotoh, Hiroyuki Miura, Ayako Shimizu, Yasuyoshi Kurokawa, Noritaka Usami

    JAPANESE JOURNAL OF APPLIED PHYSICS   60 ( SB )   2021年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP PUBLISHING LTD  

    Variable-angle spectroscopic ellipsometry analysis is performed to study the impact of post-deposition annealing on the passivation performance of the heterocontacts consisting of titanium oxide and silicon oxide on crystalline silicon (c-Si) prepared by atomic layer deposition (ALD) for the development of high-performance ALD-TiOx/SiOy/c-Si heterocontacts. The highest lifetime of 1.8 ms is obtained for the TiOx/SiOy/c-Si heterocontacts grown at 175 degrees C after annealing at 275 degrees C for 3 min. With increasing annealing temperature, the TiOx layers of the TiOx/SiOy/c-Si heterocontacts become dominant. Furthermore, the amplitude of dielectric functions of the ALD-TiOx layer decreases as annealing temperature increases, which suggests that enhanced diffusion of Ti into SiOy interlayers at higher annealing temperature. The sufficient diffusion of Ti atoms into SiOy interlayers is caused by annealing at 275 degrees C for 3 min, yielding high-quality interface passivation.

    DOI: 10.35848/1347-4065/abd6dd

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  • Mechanisms of carrier lifetime enhancement and conductivity-type switching on hydrogen-incorporated arsenic-doped BaSi2

    Sho Aonuki, Zhihao Xu, Yudai Yamashita, Kazuhiro Gotoh, Kaoru Toko, Noritaka Usami, Andrew B. Filonov, Siarhei A. Nikitsiuk, Dmitri B. Migas, Denis A. Shohonov, Takashi Suemasu

    THIN SOLID FILMS   724   138629 - 138629   2021年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE SA  

    A comparative experimental and theoretical study of the role of H incorporation in As-doped BaSi2 films has been carried out based on the experimental results that an optimal time of H treatment for the increase in photoresponsivity and carrier lifetime was in the range of 1 ? 20 min. Adequate theoretical representation of the decay curves in the framework of the model for non-radiative processes accounted for various trap-related recombination mechanisms to estimate the trap concentration to be in the range of 1.9 ? 1013 to 1.7 ? 1014 cm-3. Additionally, the extended theoretical ab initio quantum-chemical simulation of the electronic structure of the studied systems was performed. It was revealed that interstitial As atoms can mostly provide trap states in the gap while H atoms neutralize such traps. The experimentally observed unexpected switching in conductivity from n-type to p-type and vice versa in As-doped BaSi2 with H incorporation was explained to specific configurations of point defects (an As impurity with a H atom in different positions and various interatomic As-H distances) which affect the position of states in the gap.

    DOI: 10.1016/j.tsf.2021.138629

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  • Application of Bayesian optimization for improved passivation performance in TiOx/SiOy/c-Si heterostructure by hydrogen plasma treatment

    Shinsuke Miyagawa, Kazuhiro Gotoh, Kentaro Kutsukake, Yasuyoshi Kurokawa, Noritaka Usami

    APPLIED PHYSICS EXPRESS   14 ( 2 )   025503 - 025503   2021年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP PUBLISHING LTD  

    We applied hydrogen plasma treatment (HPT) on a titanium oxide/silicon oxide/crystalline silicon heterostructure to improve the passivation performance for high-efficiency silicon heterojunction solar cells. To accelerate the time-intensive process optimization of many parameters, we applied Bayesian optimization (BO). Consequently, the optimization of six process parameters of HPT was achieved by BO of only 15 cycles and 10 initial random experiments. Furthermore, the effective carrier lifetime after HPT on the optimized experimental conditions became three times higher compared with that before HPT, which certifies that BO is useful for accelerating optimization of the practical process conditions in multidimensional parameter space.

    DOI: 10.35848/1882-0786/abd869

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  • Simulation study on lateral minority carrier transport in the surface inversion layer of the p-aSi:H/i-aSi:H/cSi heterojunction solar cell

    Takefumi Kamioka, Yutaka Hayashi, Kazuhiro Gotoh, Tomohiko Hara, Ryo Ozaki, Motoo Morimura, Ayako Shimizu, Kyotaro Nakamura, Noritaka Usami, Atsushi Ogura, Yoshio Ohshita

    JAPANESE JOURNAL OF APPLIED PHYSICS   60 ( 2 )   2021年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP PUBLISHING LTD  

    The theoretical lateral current of the surface inversion layer in a crystalline silicon (cSi) surface for a p-aSi:H/i-aSi:H/cSi heterojunction (SHJ) solar cell was calculated using computer simulation and was compared with the experimental one to study defects/traps at the aSi:H/cSi interface and/or in the cSi surface and to detect the acceptor concentration (N-a) in p-aSi:H. To experimentally extract the lateral surface inversion layer current, a field-effect transistor type test element group device was co-integrated with SHJ cells on the same wafer. From the correlation between the experimental and calculated lateral surface inversion layer current, the density of defects/traps (D-it) at the aSi:H/cSi interface and/or in the cSi surface and the value of N-a were extracted. The calculated lateral surface inversion layer current stayed unchanged for various minority carrier lifetimes in the substrate, suggesting that this method is not suffered from the variation in the material parameters in the substrate.

    DOI: 10.35848/1347-4065/abdd02

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  • Activation energy of hydrogen desorption from high-performance titanium oxide carrier-selective contacts with silicon oxide interlayers

    Kazuhiro Gotoh, Takeya Mochizuki, Tomohiko Hojo, Yuki Shibayama, Yasuyoshi Kurokawa, Eiji Akiyama, Noritaka Usami

    CURRENT APPLIED PHYSICS   21   36 - 42   2021年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER  

    The impact of hydrogen desorption on the electrical properties of TiOx on crystalline silicon (c-Si) with SiOy interlayers is studied for the development of high-performance TiOx carrier-selective contacts. Compared with the TiOx/c-Si heterocontacts, a lower surface recombination velocity of 9.6 cm/s and lower contact resistivity of 7.1 m Omega cm(2) are obtained by using SiOy interlayers formed by mixture (often called SC2). The hydrogen desorption peaks arising from silicon dihydride (alpha 1) and silicon monohydride (alpha 2) on the c-Si surface of the as deposited samples are observed. The alpha 1 peak pressure of as-deposited heterocontacts with SiOx interlayers is lower than that of heterocontacts without a SiOy interlayer. Furthermore, the hydrogen desorption energies are found to be 1.76 and 2.13 eV for the TiOx/c-Si and TiOx/SC2-SiOy/c-Si heterocontacts, respectively. Therefore, the excellent passivation of the TiOx/SC2-SiOy/c-Si heterocontacts is ascribed to the relatively high rupture energy of bonding between Si and H atoms.

    DOI: 10.1016/j.cap.2020.10.002

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  • Impact of Ge deposition temperature on parameters of c-Si solar cells with surface texture formed by etching of Si using SiGe islands as a mask

    V. H. Nguyen, A. Novikov, M. Shaleev, D. Yurasov, M. Semma, K. Gotoh, Y. Kurokawa, N. Usami

    Materials Science in Semiconductor Processing   114   2020年8月

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    掲載種別:研究論文(学術雑誌)  

    In this paper, the Ge self-assembled islands grown at different temperatures were used as an etching mask for selective anisotropic etching of crystalline silicon (c-Si) in order to form a textured Si surface. The effects of Ge deposition temperature on the texture morphology as well as the parameters of c-Si solar cells fabricated on such structures were studied with the range of temperature from 500 °C to 800 °C. The textures on Si surface with low (<1 μm) etching margin were successfully fabricated for all investigated structures. It was revealed that usage of rapid annealing of Si wafer at 800 °C prior to epitaxial growth along with the low Ge deposition temperature of 500 °C allowed to achieve the relatively high effective carrier lifetime as compared to structures formed at higher (≥700 °C) temperatures thanks to the reduced degradation of Si wafer characteristics. Furthermore, the structure obtained using the lowest deposition temperature of 500 °C exhibited the highest light absorption among all studied samples thanks to the most homogeneous and most pyramidal texture morphology. As a result, the calculated short circuit current density JSC for the sample in which Ge islands were grown at 500 °C was as high as 35.89 mA/cm2. The proposed approach of surface texturing meets the requirements for thin c-Si solar cells due to small etching margin and the obtained results pave the way for increase the efficiency of thin c-Si solar cells by engineering the surface morphology to improve light absorption.

    DOI: 10.1016/j.mssp.2020.105065

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  • Impact of deposition of indium tin oxide double layers on hydrogenated amorphous silicon/crystalline silicon heterojunction

    Masanori Semma, Kazuhiro Gotoh, Markus Wilde, Shohei Ogura, Yasuyoshi Kurokawa, Katsuyuki Fukutani, Noritaka Usami

    AIP ADVANCES   10 ( 6 )   2020年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER INST PHYSICS  

    We report on the effect of sputtering deposition of indium tin oxide (ITO) as the transparent conductive oxide layer on the passivation performance of hydrogenated amorphous silicon/crystalline silicon heterojunctions. The influence of sputtering damage on passivation performance is studied by varying the ITO layer thickness from 0 nm to 80 nm. The passivation performance decreases considerably up to 10 nm and increases gradually from 20 nm to 80 nm, indicating that damage and recovery stages are present during the sputtering process. We focus on the injection energy as the cause of the recovery phenomenon. To optimize the passivation performance by intentionally enhancing the effect of the recovery stage while minimizing the initial damage at the heterointerface, we develop a two-step sputtering process in which the radiofrequency power is changed from 50 W to 100 W during deposition to prepare ITO double layers. Two step sputtering gives the lower damage, and the properties of ITO double layers are better than those of ITO single layers. These results show that two-step sputtering can realize greater a-Si:H passivation. Furthermore, better optical properties are obtained in ITO double layers compared with conventional ITO single layers. Therefore, modulating the radiofrequency power during ITO deposition can offer higher conversion efficiency.

    DOI: 10.1063/5.0009994

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  • Atomic hydrogen passivation for photoresponsivity enhancement of boron-doped p-BaSi2 films and performance improvement of boron-doped p-BaSi2/n-Si heterojunction solar cells

    Zhihao Xu, Takuma Sato, Louise Benincasa, Yudai Yamashita, Tianguo Deng, Kazuhiro Gotoh, Kaoru Toko, Noritaka Usami, Andrew B. Filonov, Dmitri B. Migas, Denis A. Shohonov, Takashi Suemasu

    JOURNAL OF APPLIED PHYSICS   127 ( 23 )   2020年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER INST PHYSICS  

    Semiconducting barium disilicide (BaSi2) is an emerging material for solar cell applications, and therefore, defect passivation is critical for improving its solar cell performance. Herein, the effect of atomic hydrogen (H) on the photoresponsivity of 500 nm-thick boron (B)-doped p-BaSi2 films was examined. The photoresponsivity reached similar to 4 A/W (about twice the highest reported value for H-passivated undoped BaSi2 films) in B-doped p-BaSi2 films exposed to an atomic H supply for 5-10min because of an increased minority-carrier lifetime, as measured by the microwave-detected photoconductivity decay. Furthermore, a >= 15 min atomic H supply was found to degrade photoresponsivity. Ab initio studies were used to interpret and understand experimental observations by analyzing states in the gap region, which can act as traps, in B-doped p-BaSi2 with H incorporation. The effect that atomic H had on the performance of B-doped p-BaSi2/n-Si heterojunction solar cells was also studied. The saturation current density was found to decrease by three orders of magnitude with the atomic H supply, and the conversion efficiency was increased up to 6.2%. Deep-level transient spectroscopy revealed a reduction of defect densities induced by the atomic H supply. Both experimental and theoretical viewpoints show that an atomic H supply is beneficial for BaSi2 solar cells.

    DOI: 10.1063/5.0005763

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  • Undoped p-type BaSi2 emitter prepared by thermal evaporation and post-annealing for crystalline silicon heterojunction solar cells

    Yuki Kimura, Kazuhiro Gotoh, Yasuyoshi Kurokawa, Noritaka Usami

    APPLIED PHYSICS EXPRESS   13 ( 5 )   2020年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP PUBLISHING LTD  

    p-type BaSi2/n-type crystalline Si (p-BaSi2/n-Si) heterojunction solar cells with various BaSi2 thickness (d(BaSi2)) from 20 to 100 nm were fabricated using a simple preparation method, that is, post-annealing of undoped n-type BaSi2 prepared by thermal evaporation. With decreasing dBaSi(2), short-circuit current density increased due to the reduction of the parasitic absorption in p-BaSi2. On the other hand, open-circuit voltage and fill factor decreased due to the increase of the leakage current. As a consequence, the solar cell with dBaSi(2) = 80 nm showed a maximum conversion efficiency. (c) 2020 The Japan Society of Applied Physics

    DOI: 10.35848/1882-0786/ab8727

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  • Significant enhancement of photoresponsivity in As-doped n-BaSi2 epitaxial films by atomic hydrogen passivation

    Sho Aonuki, Yudai Yamashita, Takuma Sato, Zhihao Xu, Kazuhiro Gotoh, Kaoru Toko, Yoshikazu Terai, Noritaka Usami, Takashi Suemasu

    APPLIED PHYSICS EXPRESS   13 ( 5 )   2020年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP PUBLISHING LTD  

    We grew 500-nm-thick lightly As-doped n-BaSi2 epitaxial films at 600 degrees C by molecular beam epitaxy, and supplied atomic H in durations (t(BaSi:H)) of 0-30 min, followed by capping with a 3-nm-thick amorphous Si layer at 180 degrees C. The photoresponsivity of the BaSi2 films was enhanced by approximately five times by As doping. Deep-level transient spectroscopy measurement revealed the disappearance of two previously reported electron traps. The photoresponsivity was further enhanced by approximately six times after H supply. It reached a maximum at t(BaSi:H) = 1-10 min, owing to the reduction of defects.

    DOI: 10.35848/1882-0786/ab8725

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  • Surface inversion layer effective minority carrier mobility as one of the measures of surface quality of the p-aSi:H/i-aSi:H/cSi heterojunction solar cell

    Takefumi Kamioka, Yutaka Hayashi, Kazuhiro Gotoh, Ryo Ozaki, Kyotaro Nakamura, Motoo Morimura, Shimako Naitou, Noritaka Usami, Atsushi Ogura, Yoshio Ohshita

    JAPANESE JOURNAL OF APPLIED PHYSICS   59   2020年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP PUBLISHING LTD  

    The lateral transport of minority carriers in the surface inversion layer of a crystalline silicon (cSi) surface for a p-aSt:H/i-aSi:H/cSi heterojunction (SHJ) solar cell was experimentally analyzed to study defects/traps at the aSi:H/cSi interface and/or on the cSi surface. To extract the lateral surface inversion layer current, a field-effect transistor type test element group device was designed and fabricated on a cSi wafer where SHJ cells were co-integrated. By analyzing the lateral surface inversion layer current, the effective surface minority carrier mobility was calculated. The extracted mobility was one order of magnitude smaller than that of a reference MoOx/i-aSi:H/cSi structure but it increased by low-temperature post-deposition annealing with respect to the reference, This method is highly sensitive to the quality of the aSi:H/cSi interface and/or the cSi surface, The density of trap sites was estimated to be of the order of 10(11) cm(-2) at the aSi:H/cSi interface and/or an the cSi surface. (C) 2020 The Japan Society of Applied physics

    DOI: 10.35848/1347-4065/ab70a0

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  • Synthesis of Mg2Si thin film by thermal treatment under inert gas atmosphere and evaluation of film quality

    Issei Horiba, Michinobu Fujiwara, Yoshihiko Nakagawa, Kazuhiro Gotoh, Yasuyoshi Kurokawa, Takashi Itoh, Noritaka Usami

    JAPANESE JOURNAL OF APPLIED PHYSICS   59   2020年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP PUBLISHING LTD  

    We report on the synthesis of Mg2Si thin films from a Mg-Si solution by thermal treatment of Mg on a Si substrate under an Ar gas atmosphere. The Mg was prepared by two methods. One is to deposit Mg films by thermal evaporation, and another is to simply place Mg ribbons on Si. After thermal treatment, a two-layer structure consisting of oxide and similar to 1 mu m-thick Mg2Si films with {100} preferential orientation was observed for the sample prepared by thermal evaporation. On the other hand, similar to 10 mu m-thick single layer Mg2Si with more random orientations and cracks was formed for the Mg ribbon contact samples. Possible mechanisms for different structures, crystal orientations, and crack formation are discussed. (c) 2020 The Japan Society of Applied Physics

    DOI: 10.35848/1347-4065/ab6b79

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  • Drastic enhancement of photoresponsivity in C-doped BaSi<inf>2</inf> films formed by radio-frequency sputtering

    T. Nemoto, S. Matsuno, T. Sato, K. Gotoh, M. Mesuda, H. Kuramochi, K. Toko, N. Usami, T. Suemasu

    Japanese Journal of Applied Physics   59 ( SF )   2020年4月

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    掲載種別:研究論文(国際会議プロシーディングス)  

    We formed carbon (C)-doped BaSi2 films by RF sputtering of BaSi2 and SiC targets simultaneously, and measured their optical properties. In the Raman spectra of BaSi2 films, peaks corresponding to vibrational modes of Si tetrahedra in the lattice of BaSi2 appear. On the other hand, in C-doped BaSi2 films, new peaks at around 260, 310, and 630 cm-1 other than those of BaSi2 films were observed. As the RF power of the SiC target (P SiC) increased, these intensities increased. The absorption edge of C-doped BaSi2 films was shifted to higher energies from 1.19 to 1.30 eV with increasing P SiC. We achieved the highest photoresponsivity of 1 A W-1 ever achieved for BaSi2 films at a bias voltage of 0.1 V applied between the top and bottom electrodes. The marked enhancement of photoresponsivity was interpreted to originate from the increased carrier lifetime in C-doped BaSi2 films.

    DOI: 10.35848/1347-4065/ab69dc

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  • Effects of evaporation vapor composition and post-annealing conditions on carrier density of undoped BaSi2 evaporated films

    Yuki Kimura, Michinobu Fujiwara, Yoshihiko Nakagawa, Kazuhiro Gotoh, Yasuyoshi Kurokawa, Noritaka Usami

    JAPANESE JOURNAL OF APPLIED PHYSICS   59   2020年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP PUBLISHING LTD  

    The effects of vapor composition during evaporation and post-annealing conditions on the carrier density of undoped BaSi2 films were investigated. Regardless of the vapor composition during evaporation, the carrier density after post-annealing changed in the range between 10(16) and 10(17) cm(-3) by changing the post-annealing temperature. In addition, post-annealing above 920 degrees C induced carrier type transition from n-type to ptype. The temperature at which the carrier type transition occurred was found to depend on the surface covering material during post-annealing, which implies that the carrier type transition could originate from the change of the BaSi2 film composition to Si-rich. (c) 2020 The Japan Society of Applied Physics

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  • Effect of forming gas annealing on hydrogen content and surface morphology of titanium oxide coated crystalline silicon heterocontacts

    Yuta Nakagawa, Kazuhiro Gotoh, Markus Wilde, Shohei Ogura, Yasuyoshi Kurokawa, Katsuyuki Fukutani, Noritaka Usami

    JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A   38 ( 2 )   2020年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:A V S AMER INST PHYSICS  

    Crystalline silicon (c-Si) heterojunction solar cells using carrier-selective contacts have drawn considerable attention due to their high power conversion efficiency with a simple fabrication process. Titanium oxide (TiOx) is one of the most promising materials that can provide excellent surface passivation as well as carrier-selective transport. In this study, the authors fabricate the TiOx/SiOx/c-Si heterocontacts by atomic layer deposition (ALD) and investigate the effect of the forming gas annealing (FGA) on hydrogen content and surface morphology by utilizing nuclear reaction analysis (NRA) and atomic force microscope (AFM) measurements, respectively. The highest effective carrier lifetime (tau(eff)) of 891 mu s is realized for TiOx/SiOx/c-Si heterocontacts after FGA at 400 degrees C for 3 min, indicating that high surface passivation performance is obtained. NRA clarifies that the hydrogen content in the TiOx/SiOx/c-Si heterocontacts decreases with increasing FGA temperature and duration. With increasing FGA temperature and duration, also the surfaces of the TiOx/SiOx/c-Si heterocontacts are roughened, which means enhanced crystallization of the TiOx/SiOx/c-Si heterocontacts. From the NRA and AFM analyses, the authors conclude that there is a trade-off relationship between the hydrogen content in the TiOx/SiOx/c-Si heterocontacts and the crystallization of the TiOx layers.

    DOI: 10.1116/1.5134719

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  • Effect of hydrogen plasma treatment on the passivation performance of TiOx on crystalline silicon prepared by atomic layer deposition

    Shinsuke Miyagawa, Kazuhiro Gotoh, Shohei Ogura, Markus Wilde, Yasuyoshi Kurokawa, Katsuyuki Fukutani, Noritaka Usami

    JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A   38 ( 2 )   2020年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:A V S AMER INST PHYSICS  

    The authors report on the effect of hydrogen plasma treatment (HPT) on the passivation performance of titanium oxide (TiOx) on crystalline silicon (c-Si) fabricated by atomic layer deposition. Recently, TiOx has gathered attention as an electron-selective contact material for silicon heterojunction (SHJ) solar cells due to its preferable work function and band lineup. Moreover, TiOx has excellent light transmission properties due to its large bandgap energy. In order to improve the power conversion efficiency of SHJ solar cells with TiOx, it is necessary to enhance the passivation performance. The effective carrier lifetime representing the passivation performance is enhanced by HPT and amounts to 407.2 mu s after HPT at 200 degrees C for 1min. This value is twice as high as after forming gas annealing, which is the standard method to enhance the passivation performance of TiOx/c-Si heterostructures. Nuclear reaction analysis clarifies that the hydrogen concentration (C-H) at the TiOx/c-Si interface of the HPT-processed sample is higher than that of an as-deposited sample and that the peak position of the C-H distribution is shifted closer to the TiOx/c-Si heterointerface after HPT. Moreover, thermal desorption spectroscopy shows that Si-H and Si-H-2 hydrogen bonds increase with HPT. These results indicate that the atomic hydrogen produced by the hydrogen plasma diffuses toward the TiOx/c-Si interface and terminate the local dangling bonds, which is responsible for the improved passivation performance.

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  • Effect of the Niobium-Doped Titanium Oxide Thickness and Thermal Oxide Layer for Silicon Quantum Dot Solar Cells as a Dopant-Blocking Layer

    Ryushiro Akaishi, Kohei Kitazawa, Kazuhiro Gotoh, Shinya Kato, Noritaka Usami, Yasuyoshi Kurokawa

    NANOSCALE RESEARCH LETTERS   15 ( 1 )   2020年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:SPRINGEROPEN  

    Silicon quantum dot (Si-QD) embedded in amorphous silicon oxide is used for p-i-n solar cell on quartz substrate as a photogeneration layer. To suppress diffusion of phosphorus from an n-type layer to a Si-QD photogeneration layer, niobium-doped titanium oxide (TiOx:Nb) is adopted. Hydrofluoric acid treatment is carried out for a part of the samples to remove the thermal oxide layer in the interface of TiOx:Nb/n-type layer. The thermal oxide acts as a photo-generated carrier-blocking layer. Solar cell properties using 10-nm-thick TiOx:Nb without the thermal oxide are better than those with the thermal oxide, notably short circuit current density is improved up to 1.89 mA/cm(2). The photo-generated carrier occurs in Si-QD with quantum confinement effect. The 10-nm-thick TiOx:Nb with the thermal oxide layer effectively blocks P; however, P-diffusion is not completely suppressed by the 10-nm-thick TiOx:Nb without the thermal oxide. These results indicate that the total thickness of TiOx:Nb and thermal oxide layer influence the P-blocking effect. To achieve the further improvement of Si-QD solar cell, over 10-nm-thick TiOx:Nb is needed.

    DOI: 10.1186/s11671-020-3272-8

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  • Fabrication of silicon-nanocrystals-embedded silicon oxide passivating contacts

    Ryohei Tsubata, Kazuhiro Gotoh, Yasuyoshi Kurokawa, Noritaka Usami

    2020 47TH IEEE PHOTOVOLTAIC SPECIALISTS CONFERENCE (PVSC)   969 - 972   2020年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    We apply silicon nanocrystals as a carrier transport route in silicon oxide for polycrystalline silicon on oxide (POLO) junctions. The Si nanocrystals are formed in silicon oxide by deposition of hydrogenated amorphous silicon oxide with different oxygen concentration and subsequent annealing. From cross-sectional transmission electron microscopy (TEM) images, the Si nanocrystals are observed for the sample at annealing temperature of 750 degrees C. The highest average effective lifetime of about 630 mu s and contact resistivity of 25.5 m Omega.cm are obtained before hydrogenation process.

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  • Work function of indium oxide thin films on p-type hydrogenated amorphous silicon

    Masanori Semma, Kazuhiro Gotoh, Yasuyoshi Kurokawa, Noritaka Usami

    2020 47TH IEEE PHOTOVOLTAIC SPECIALISTS CONFERENCE (PVSC)   124 - 127   2020年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    We investigate an influence of thermal treatment on the properties of tin-doped indium oxide (ITO) and In2O3 on glass and hydrogenated amorphous silicon (a-Si:H)/glass. Work function (WF), electron density and mobility of the In2O3 are dependent on a-Si:H underlayer possibly due to H diffusion from -Si:H underlayer by annealing. In addition, WF of the In2O3 is higher than that of the ITO regardless of presence of a-Si:H underlayer. Furthermore, the ITO/In2O3 double layers are fabricated for silicon heterojunction (SHJ) solar cells. The electrical and optical properties of the ITO/In2O3 stacks are adequate for transparent conductive oxide (TCO) layer.

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  • Tuning the Electrical Properties of Titanium Oxide Bilayers Prepared by Atomic Layer Deposition at Different Temperatures

    Kazuhiro Gotoh, Takeya Mochizuki, Yasuyoshi Kurokawa, Noritaka Usami

    PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE   216 ( 22 )   1900495 - 1900495   2019年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WILEY-V C H VERLAG GMBH  

    Carrier-selective contacts prepared by atomic layer deposition (ALD) have received significant attention for developing high-efficiency solar cells. Herein, the electrical properties of titanium oxide (TiOx) prepared by ALD are manipulated by modulating the deposition temperature during ALD. Tunable electrical properties are possible due to the existence of oxygen vacancies in TiOx prepared at low deposition temperatures. TiOx layers prepared at 100 and 150 degrees C provide a low contact resistivity and high passivation performance, respectively. A high carrier selectivity of 13.5 is achieved by stacking the TiOx layers prepared at 100 and 150 degrees C, compared with a single TiOx layer. Modulating the deposition temperature can, therefore, improve the electrical properties of ALD-TiOx. This approach can be used to optimize the functionality of ALD-based materials.

    DOI: 10.1002/pssa.201900495

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  • Hydrogen concentration at a-Si:H/c-Si heterointerfaces-The impact of deposition temperature on passivation performance

    Kazuhiro Gotoh, Markus Wilde, Shinya Kato, Shohei Ogura, Yasuyoshi Kurokawa, Katsuyuki Fukutani, Noritaka Usami

    AIP ADVANCES   9 ( 7 )   075115 - 075115   2019年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER INST PHYSICS  

    We studied the effect of deposition temperature on the hydrogen distribution and the passivation performance of hydrogenated amorphous silicon (a-Si:H) coated crystalline silicon (c-Si) heterojunctions as a model of high efficiency solar cell structures. Nuclear reaction analysis (NRA) was employed to obtain hydrogen depth profiles of the heterojunctions prepared at temperatures from 80 to 180 degrees C. The implied open circuit voltage (i-V-OC) and carrier lifetime monotonically increased with increasing deposition temperature in the as-deposited samples. NRA clarified that the hydrogen concentration (C-H) at the a-Si:H/c-Si interface and in the a-Si:H layer decreased with deposition temperature. The hydrogen concentration around the interface was roughly 3 x 10(21) cm(-3) for the sample deposited at 180 degrees C. The NRA results are supplemented by optical constants obtained with spectroscopic ellipsometry (SE). At higher growth temperature, larger refractive indices and extinction coefficients were confirmed by SE analysis, suggesting that fewer hydrogen atoms are incorporated into the a-Si:H layers prepared at higher growth temperature. Furthermore, the passivation performance was enhanced by post deposition annealing (PDA) at 200 degrees C for 30 min. No significant change of the hydrogen distribution and optical constants was observed after PDA, suggesting that improved passivation is due to a local rearrangement of hydrogen at the molecular level that results in enhanced hydrogenation of dangling bonds.

    DOI: 10.1063/1.5100086

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  • Evidence of solute PEDOT:PSS as an efficient passivation material for fabrication of hybrid c-Si solar cells

    Van Hoang Nguyen, Shinya Kato, Kazuhiro Gotoh, Yasuyoshi Kurokawa, Noritaka Usami

    SUSTAINABLE ENERGY & FUELS   3 ( 6 )   1448 - 1454   2019年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ROYAL SOC CHEMISTRY  

    A new aspect of solute PEDOT:PSS was explored, its function as an excellent passivation material. Solute PEDOT:PSS with a thickness of 9.4 nm exhibited an effective carrier lifetime of 940 mu s at an injection level of 1 x 10(14) cm(-3). A new architecture of hybrid crystalline silicon solar cells with highly conductive PEDOT:PSS on the front side and solute PEDOT:PSS on the backside was demonstrated. The reverse saturation current density Jo of 9.4 nm-thick solute PEDOT:PSS was evaluated as 2.2 x 10(-14) A cm(-2), which is ten times lower than that without solute PEDOT:PSS on the backside, 1.45 x 10(-13) A cm(-2). With the introduction of 7.5 nm-thick solute PEDOT:PSS on the backside, the performance drastically improved with an open-circuit voltage V-OC of 618 mV, short-circuit current density J(SC) of 28.33 mA cm(-2) and power conversion efficiency E-ff of 11.45% owing to efficient passivation. Employment of solute PEDOT:PSS as an efficient passivation material opens a new route for the fabrication of hybrid c-Si solar cells, which is facile, reproducible and environmentally friendly.

    DOI: 10.1039/c9se00093c

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  • Marked enhancement of the photoresponsivity and minority-carrier lifetime of BaSi2 passivated with atomic hydrogen

    Zhihao Xu, Denis A. Shohonov, Andrew B. Filonov, Kazuhiro Gotoh, Tianguo Deng, Syuta Honda, Kaoru Toko, Noritaka Usami, Dmitri B. Migas, Victor E. Borisenko, Takashi Suemasu

    PHYSICAL REVIEW MATERIALS   3 ( 6 )   2019年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER PHYSICAL SOC  

    Passivation of barium disilicide (BaSi2) films is very important for their use in solar cell applications. In this paper, we demonstrated the effect of hydrogen (H) passivation on both the photoresponsivity and minority-carrier lifetime of BaSi2 epitaxial films grown by molecular beam epitaxy. First, we examined the growth conditions of a 3-nm-thick hydrogenated amorphous silicon (a-Si) capping layer formed on a 500-nm-thick BaSi2 film and found that an H supply duration (ta-Si:H) of 15 min at a substrate temperature of 180 degrees C sizably enhanced the photoresponsivity of the BaSi2 film. We next supplied atomic H to BaSi2 epitaxial films at 580 degrees C and changed supply duration (t(BaSi;H)) in the range of 1-30 min, followed by capping with an a-Si layer. The photoresponsivity of the films changed considerably depending on t(BaSi;H )and reached a maximum of 2.5 A/W at a wavelength of 800 nm for the sample passivated for t(BaSi;H )= 15 min under a bias voltage of 0.3 V applied to the front-surface indium-tin-oxide electrode with respect to the back-surface aluminum electrode. This photoresponsivity is approximately one order of magnitude higher than the highest value previously reported for BaSi2. Microwave photoconductivity decay measurements revealed that the minority-carrier lifetime of the BaSi2 film with the highest photoresponsivity was 14 mu s, equivalent to its bulk carrier lifetime ever reported. We performed theoretical analyses based on a rate equation including several recombination mechanisms and reproduced the experimentally obtained decay curves. We also calculated the total density of states of BaSi2 by ab initio studies when one Si vacancy existed in a unit cell and one, two, and three H atoms occupied Si vacancy or interstitial sites. A Si vacancy caused a localized state with two energy bands to appear close to the middle of the band gap. In certain cases, H passivation of the Si dangling bonds can markedly decrease trap concentration. From both experimental and theoretical viewpoints, we conclude that an atomic H supply is beneficial for BaSi2 solar cells.

    DOI: 10.1103/PhysRevMaterials.3.065403

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  • Epitaxial growth of SiGe on Si substrate by printing and firing of Al-Ge mixed paste

    Shogo Fukami, Yoshihiko Nakagawa, Mel E. Hainey, Kazuhiro Gotoh, Yasuyoshi Kurokawa, Masahiro Nakahara, Marwan Dhamrin, Noritaka Usami

    JAPANESE JOURNAL OF APPLIED PHYSICS   58 ( 4 )   2019年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP PUBLISHING LTD  

    We report on a simple liquid-phase epitaxy (LPE) of SiGe on Si (100) substrate based on printing and firing. LPE was performed using an Al-Ge mixed paste screen-printed on a Si (100) substrate followed by annealing above the Al-Ge eutectic temperature in air or in an Ar atmosphere. In the case of annealing in air at 800 degrees C, SiGe was formed between the mixed paste and the surface of the Si substrate. However, a wave-like oxide film was confirmed at the SiGe/Si interface, which hindered the growth of SiGe. On the other hand, annealing in the Ar atmosphere at 800 degrees C led to the successful formation of a more continuous, thicker SiGe film by suppressing the oxidation of Al. It can be concluded that LPE growth using printing and firing of Al-Ge mixed paste is a suitable method to grow SiGe with a low-cost and simple high-speed process. (C) 2019 The Japan Society of Applied Physics

    DOI: 10.7567/1347-4065/ab00e5

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  • Impact of size distributions of Ge islands as etching masks for anisotropic etching on formation of anti-reflection structures

    Yushi Ota, Dmitry Yurasov, Alexey Novikov, Mikhail Shaleev, Kazuhiro Gotoh, Yasuyoshi Kurokawa, Noritaka Usami

    JAPANESE JOURNAL OF APPLIED PHYSICS   58 ( 4 )   2019年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP PUBLISHING LTD  

    The impact of the size distributions of Ge islands on the structural and optical characteristics of anti-reflection structures was investigated. The variation of island size distribution was achieved through the variation of growth temperature in gas-source molecular beam epitaxy at 700 degrees C-800 degrees C. Ge islands were utilized as etching masks to form the anti-reflection structures. By using lower growth temperature of 700 degrees C and subsequent etching, larger texture without many hollows was formed in contrast to that using 800 degrees C. Broader size distribution of islands formed at 700 degrees C was found to lead to larger texture size. Smaller texture is formed by smaller islands and short etching, whereas larger texture is formed by erosion of smaller texture during long etching. A potential short-circuit current density of 36.75 mA cm(-2) was obtained for the sample by the islands grown at 700 degrees C with reduced etching margins, comparable to that of conventional pyramid textures. (C) 2019 The Japan Society of Applied Physics

    DOI: 10.7567/1347-4065/ab003b

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  • Silicon Nanowire Heterojunction Solar Cells with an Al2O3 Passivation Film Fabricated by Atomic Layer Deposition

    Shinya Kato, Yasuyoshi Kurokawa, Kazuhiro Gotoh, Tetsuo Soga

    NANOSCALE RESEARCH LETTERS   14   2019年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:SPRINGER  

    Silicon nanowires (SiNWs) show a great potential for energy applications because of the optical confinement effect, which enables the fabrication of highly efficient and thin crystalline silicon (c-Si) solar cells. Since a 10-m-long SiNW array can absorb sufficient solar light less than 1200nm, the 10-m-long SiNW was fabricated on Si wafer to eliminate the influence of the Si wafer. On the other hand, Surface passivation of the SiNWs is a crucial problem that needs to be solved to reduce surface recombination and enable the application of SiNWs to c-Si solar cells. In this study, aluminum oxide (Al2O3) was fabricated by atomic layer deposition for the passivation of dangling bonds. However, owing to a complete covering of the SiNWs with Al2O3, the carriers could not move to the external circuit. Therefore, chemical-mechanical polishing was performed to uniformly remove the oxide from the top of the SiNWs. A heterojunction solar cell with an efficiency of 1.6% was successfully fabricated using amorphous silicon (a-Si). The internal quantum efficiencies (IQE) of the SiNW and c-Si solar cells were discussed. In the wavelength region below 340nm, the IQE of the SiNW solar cell is higher than that of the c-Si device, which results in an increase of the absorption of the SiNW cells, suggesting that SiNWs are promising for crystalline-silicon thinning.

    DOI: 10.1186/s11671-019-2930-1

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  • Fabrication of a Silicon Nanowire Solar Cell on a Silicon-on-Insulator Substrate

    Shinya Kato, Yasuyoshi Kurokawa, Kazuhiro Gotoh, Tetsuo Soga

    APPLIED SCIENCES-BASEL   9 ( 5 )   2019年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:MDPI  

    This study proposes metal-assisted chemical etching (MAE) as a facile method to fabricate silicon nanowire (SiNW) array structures, with high optical confinement for thin crystalline silicon solar cells. Conventional SiNW arrays are generally fabricated on Si wafer substrates. However, tests on conventional SiNW-based solar cells cannot determine whether the photo-current is derived from SiNWs or from the Si wafer. Herein, SiNW arrays were fabricated on a silicon-on-insulator substrate with a 10-mu m-thick silicon layer for measuring the photo-current of the SiNW only. The 9 mu m-long p-type SiNW arrays were applied to a solar cell structure fabricated using an n-type H-doped amorphous Si layer, thereby confirming the photovoltaic effect. However, the device exhibited a conversion efficiency of 0.0017% because of a low short-circuit current (J(sc)) and a low open-circuit voltage (V-oc). The low J(sc) resulted from a high series resistance and high absorption loss from the amorphous Si layer, whereas the low V-oc resulted from the high surface recombination velocity of the SiNW array structure. Therefore, reducing the surface recombination of SiNW-based solar cells can improve their conversion efficiency.

    DOI: 10.3390/app9050818

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  • Local Structure of High Performance TiOx Electron-Selective Contact Revealed by Electron Energy Loss Spectroscopy

    Takeya Mochizuki, Kazuhiro Gotoh, Yasuyoshi Kurokawa, Takahisa Yamamoto, Noritaka Usami

    ADVANCED MATERIALS INTERFACES   6 ( 3 )   2019年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WILEY  

    Recent increases in the power conversion efficiency of crystalline silicon (c-Si) heterojunction (SHJ) solar cells are due to implementation of carrier-selective contacts (CSCs) with high passivation performance and low contact resistivity. These electrical properties of CSCs significantly depend on the nature of the CSCs/c-Si interface at the atomistic scale, and precise control of the interface with the SiOx interlayer is the key to obtaining superior electrical properties. It is shown that a TiOx/c-Si structure with an interlayer prepared by nitric acid at room temperature shows the best performance among points with five different interlayer formation methods. The underlying mechanisms are investigated by combining high-resolution transmission electron microscopy and electron energy loss (EEL) spectroscopy. The EEL spectra reveal that the Si:O ratio of an as-deposited SiOx interlayer is nonstoichiometric (x < 2), which could contribute to lower contact resistivity. Furthermore, the as-deposited SiOx leads to formation of a Ti containing SiOx layer with few oxygen vacancies after forming gas annealing, resulting in the significant enhancement of passivation performance. These results show that the control of the interlayer with atomistic scale is of crucial importance to realize higher power conversion efficiency of SHJ solar cells.

    DOI: 10.1002/admi.201801645

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  • Significant improvement on electrical properties of BaSi2 due to atomic H passivation by radio-frequency plasma

    Zhihao Xu, Kazuhiro Gotoh, Tianguo Deng, Kaoru Toko, Noritaka Usami, Takashi Suemasu

    2019 IEEE 46TH PHOTOVOLTAIC SPECIALISTS CONFERENCE (PVSC)   12 - 14   2019年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    Passivation of BaSi2 film is very important for their use in solar cell applications. In this paper, we demonstrated the effect of hydrogen (H) passivation on both the photoresponsivity and minority-carrier lifetime of BaSi2 epitaxial films grown by molecular beam epitaxy. We supplied atomic H to BaSi2 epitaxial films at 580 degrees C and changed supply duration (t(H)) in the range of 0-30 min, followed by capping with an amorphous Si (a-Si) layer. The photoresponsivity of films changed considerably depending on t(H) and reached a maximum of 2.5 A/W at a wavelength of 800 nm for the sample passivated for t(H) = 15 min under the bias voltage of 0.3 V applied to the front-surface indium-tin-oxide electrode with respect to the back-surface aluminum electrode. This photoresponsivity is approximately one order of magnitude higher than the highest value previously reported for BaSi2 . Furthermore, microwave photoconductivity decay measurements revealed that the minority-carrier lifetime of the BaSi2 film with the highest photoresponsivity was 14 mu s, equivalent to its bulk carrier lifetime ever reported.

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  • Electrical properties of TiOx bilayer prepared by atomic layer deposition at different temperatures 査読

    Takeya Mochizuki, Kazuhiro Gotoh, Yasuyoshi Kurokawa, Noritaka Usami

    Proceedings for IEEE-PVSC2019   2019年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

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  • Activation mechanism of TiOx passivating layer on crystalline Si

    Takeya Mochizuki, Kazuhiro Gotoh, Akio Ohta, Shohei Ogura, Yasuyoshi Kurokawa, Seiichi Miyazaki, Katsuyuki Fukutani, Noritaka Usami

    APPLIED PHYSICS EXPRESS   11 ( 10 )   2018年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP PUBLISHING LTD  

    We report on the activation mechanism of titanium oxide (TiOx) prepared by atomic layer deposition on crystalline silicon (c-Si), which is regarded as a prominent electron-selective contact with ideal band alignment and low carrier recombination for Si heterojunction solar cells. The activation energy of surface passivation was revealed to be about 0.37 eV, which was shown to be associated with the marked transformation of the chemical bonding states at the TiOx/c-Si interface. Detailed analysis confirmed that Si-O bonds are formed after postannealing, owing to the dissociation of the Si-H and Si-H-2 bonds at the interface and subsequent termination by oxygen atoms. (C) 2018 The Japan Society of Applied Physics

    DOI: 10.7567/APEX.11.102301

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  • Fabrication of light-trapping structure by selective etching of thin Si substrates masked with a Ge dot layer and nanomasks

    Atsushi Hombe, Yasuyoshi Kurokawa, Kazuhiro Gotoh, Seimei Akagi, Yuzo Yamamoto, Dmitry Yurasov, Alexey Novikov, Noritaka Usami

    JAPANESE JOURNAL OF APPLIED PHYSICS   57 ( 8 )   2018年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP PUBLISHING LTD  

    A light-trapping structure was fabricated on crystalline Si wafers. In this method, a Ge/Si(001) self-assembled dot structure was etched using KOH and a commercial alkaline solution including nanomask particles. Many nanoscale islands were formed by adding the nanomask particles. The enhancement of light absorption was successfully confirmed in samples with nanostructures after etching. Since the etching margin of a nanostructure was less than 2 mu m, the nanostructure could be applied to an ultrathin Si substrate. To investigate the effect of surface passivation on the nanostructure, the nanostructure was passivated using hydrogenated amorphous Si thin films by plasma-enhanced chemical vapor deposition. By quasi-steady-state photoconductance measurement, the suitable implied open-circuit voltage and implied fill factor for heterojunction solar cells were obtained. From calculations based on these parameters, solar cells with nanostructures at a substrate thickness of 100 mu m are expected to have a conversion efficiency of 23.21%. (C) 2018 The Japan Society of Applied Physics.

    DOI: 10.7567/JJAP.57.08RF09

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  • Impact of boron incorporation on properties of silicon solar cells employing p-type polycrystalline silicon grown by aluminum-induced crystallization

    Shota Masuda, Kazuhiro Gotoh, Isao Takahashi, Kyotaro Nakamura, Yoshio Ohshita, Noritaka Usami

    JAPANESE JOURNAL OF APPLIED PHYSICS   57 ( 8 )   2018年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP PUBLISHING LTD  

    We report on our attempt to increase the carrier density in the p-type polycrystalline silicon (poly-Si) layers grown by aluminum-induced crystallization (AIC) employing a B-doped Si target. Hall measurement revealed that we could obtain a lower-resistance and heavily doped p-type continuous poly-Si thin layer formed by AIC using B-doped a-Si. According to our evaluation of tunnel oxide passivated contact (TOPCon) solar cells with AIC-grown poly-Si, the AIC-TOPCon solar cells fabricated at 570 degrees C using B-doped a-Si showed higher conversion efficiency of 13.5% than that of 12.8% when using nondoped a-Si. It is considered that the cell characteristics, particularly FF and V-oc, were improved owing to the lower series resistance and higher carrier density since both Al and B were successfully incorporated into the AIC-grown poly-Si. (C) 2018 The Japan Society of Applied Physics

    DOI: 10.7567/JJAP.57.08RB12

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  • Effect of substrate type on the electrical and structural properties of TiO2 thin films deposited by reactive DC sputtering

    Xuemei Cheng, Kazuhiro Gotoh, Yoshihiko Nakagawa, Noritaka Usami

    JOURNAL OF CRYSTAL GROWTH   491   120 - 125   2018年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    Electrical and structural properties of TiO2 thin films deposited at room temperature by reactive DC sputtering have been investigated on three different substrates: high resistivity (>1000 Omega cm) float zone Si(1 1 1), float zone Si(1 00) and alkali free glass. As-deposited TiO2 films on glass substrate showed extremely high resistivity of (similar to 5.5 x 10(3) Omega cm). In contrast, lower resistivities of similar to 2 Omega cm and similar to 5 Omega cm were obtained for films on Si(1 1 1) and Si(1 0 0), respectively. The as-deposited films were found to be oxygen-rich amorphous TiO2 for all the substrates as evidenced by X-ray photoemission spectroscopy and X-ray diffraction. Subsequent annealing led to appearance of anatase TiO2 on Si but not on glass. The surface of as-deposited TiO2 on Si was found to be rougher than that on glass. These results suggest that the big difference of electrical resistivity of TiO2 would be related with existence of more anatase nuclei forming on crystalline substrates, which is consistent with the theory of charged clusters that smaller clusters tend to adopt the substrate structure. (C) 2018 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jcrysgro.2018.04.001

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  • Improving the photoresponse spectra of BaSi2 layers by capping with hydrogenated amorphous Si layers prepared by radio-frequency hydrogen plasma

    Zhihao Xu, Kazuhiro Gotoh, Tianguo Deng, Takuma Sato, Ryota Takabe, Kaoru Toko, Noritaka Usami, Takashi Suemasu

    AIP ADVANCES   8 ( 5 )   2018年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER INST PHYSICS  

    We studied the surface passivation effect of hydrogenated amorphous silicon (a-Si:H) layers on BaSi2 films. a-Si: H was formed by an electron-beam evaporation of Si, and a supply of atomic hydrogen using radio-frequency plasma. Surface passivation effect was first investigated on a conventional n-Si(111) substrate by capping with 20 nm-thick a-Si: H layers, and next on a 0.5 mu m-thick BaSi2 film on Si(111) by molecular beam epitaxy. The internal quantum efficiency distinctly increased by 4 times in a wide wavelength range for sample capped in situ with a 3 nm-thick a-Si: H layer compared to those capped with a pure a-Si layer. (C) 2018 Author(s).

    DOI: 10.1063/1.5025021

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  • EFFECT OF NOVEL SUB-MICRON STRUCTURE FABRICATED ONTO CRYSTALLINE SILICON ON OPTICAL PROPERITES AND MINORITY CARRIER LIFETIME 査読

    Sei Miki, Kurokawa Yasuyoshi, Kato Shinya, Gotoh Kazuhiro, Usami Noritaka

    グランド再生可能エネルギー国際会議論文集   1 ( 0 )   2018年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    To obtain high efficiency in crystalline silicon thin film solar cells, it is necessary to obtain novel light trapping structure, which has not only high light scattering effect and small etching margin but also has low surface recombination. Our previous calculation results revealed that silicon nanowires (SiNWs) with submicron diameters have large light scattering effect. In this study, to verify the simulation results, SiNWs with submicron diameters were successfully fabricated by metal assisted chemical etching (MACE) method with silica particles as etching masks. Optical properties and minority carrier lifetime of the obtained structures were measured, and these results suggest that SiNWs with submicron diameters are effective for both of light trapping and suppression of surface recombination.

    DOI: 10.24752/gre.1.0_46

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  • Deposition and Characterization of Si Quantum Dot Multilayers Prepared by Plasma Enhanced Chemical Vapor Deposition using SiH4 and CO2 Gases

    Ryushiro Akaishi, Kouhei Kitazawa, Satoshi Ono, Kazuhiro Gotoh, Eiji Ichihara, Shinya Kato, Noritaka Usami, Yasuyoshi Kurokawa

    2018 IEEE 7TH WORLD CONFERENCE ON PHOTOVOLTAIC ENERGY CONVERSION (WCPEC) (A JOINT CONFERENCE OF 45TH IEEE PVSC, 28TH PVSEC & 34TH EU PVSEC)   2852 - 2856   2018年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    To obtain silicon quantum dot (Si-QD) multilayers, amorphous silicon oxide (a-SiOx) films have been prepared by plasma enhanced chemical vapor deposition (PECVD) using SiH4 and CO2. As increasing CO2 flow rate, crystal volume of Si was decreased and optical gap was increased. This results suggest the increasing of oxygen content in samples. From this analysis, Si-QD multilayers having different Si-QD size were fabricated and were evaluated for structural properties. A cross-sectional transmission electron microscopy image showed the formation of Si-QDs with the diameter of about 5 nm. PL spectra showed the bandgap was blue-shifted to 1.3 eV with decreasing the size of Si-QDs to 5 nm, indicating the quantum size effect appeared in these samples.

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  • Stacks of a-SiOx:H/a-Si:H Passivation Layer for Low Parasitic Absorption and High Passivation in Silicon Heterojunction Solar Cells 査読

    K. Gotoh, M. Cui, R. Akaishi, Y. Kurokawa, N. Usami

    Proceedings for EUPVSEC2018   2018年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

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  • Local Structure of High Performance TiOx Passivating Layer Revealed by Electron Energy Loss Spectroscopy

    Takeya Mochizuki, Kazuhiro Gotoh, Akio Ohta, Yasuyoshi Kurokawa, Seiichi Miyazaki, Takahisa Yamamoto, Noritaka Usami

    2018 IEEE 7TH WORLD CONFERENCE ON PHOTOVOLTAIC ENERGY CONVERSION (WCPEC) (A JOINT CONFERENCE OF 45TH IEEE PVSC, 28TH PVSEC & 34TH EU PVSEC)   3896 - 3899   2018年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    We investigated the local structure at the interface between titanium oxide (TiOx) and crystalline Si (c-Si) with silicon oxide (SiOx) interlayers by employing the electron energy loss (EEL) spectroscopy to clarify the origin of the high performance TiOx passivating layer deposited by atomic layer deposition. Five kinds of TiOx/SiOx/c-Si structures were fabricated and the best passivation performance was achieved by the SiOx interlayer formed by nitric acid at room temperature. EEL spectra revealed that Ti-contained more stoichiometric SiOx including few oxygen vacancies and Ti-O-Si bonding would be formed after forming gas annealing, resulting in the enhancement of passivation performance.

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  • Improving Intrinsic Silicon Nanoparticle Film by Press Treatment for use in p-i n Solar Cells

    Eiji Ichihara, Shinya Kato, Ryushiro Akaishi, Kazuhiro Gotoh, Yasuyoshi Kurokawa, Naoki Kishi, Tetsuo Soga

    2018 IEEE 7TH WORLD CONFERENCE ON PHOTOVOLTAIC ENERGY CONVERSION (WCPEC) (A JOINT CONFERENCE OF 45TH IEEE PVSC, 28TH PVSEC & 34TH EU PVSEC)   0317 - 0320   2018年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    An intrinsic silicon nanoparticle (i-SiNP) layer was fabricated using the spin-coating technique and utilized as the active layer of a solar cell. The electrical conductivity of the i-SiNP layer was enhanced via press treatment, which increased the density and electrical conductivity of the SiNPs. Raman spectroscopy and electron-spin resonance results indicated that the SiNPs were only in contact with each other and were not bound together. To fabricate a solar cell with an i-SiNP active layer, a-Si was used to synthesize the p- and n-type doping layers. The open-circuit voltage of the cell was 140mV.

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  • Photoresponsivity improvement of BaSi2 epitaxial films by capping with hydrogenated amorphous Si layers by radio-frequency H-2 plasma

    Zhihao Xu, Kazuhiro Gotoh, Tianguo Deng, Takuma Sato, Kaoru Toko, Noritaka Usami, Takashi Suemasu

    2018 IEEE 7TH WORLD CONFERENCE ON PHOTOVOLTAIC ENERGY CONVERSION (WCPEC) (A JOINT CONFERENCE OF 45TH IEEE PVSC, 28TH PVSEC & 34TH EU PVSEC)   1871 - 1873   2018年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    The surface passivation effect of hydrogenated amorphous silicon (a-Si:H) layers on BaSi2 film was studied. a-Si: H layers were formed by electron-beam evaporation of Si and subsequent or simultaneous supply of atomic hydrogen using a radio-frequency (RF) plasma generator. The hydrogen concentration in a-Si: H layers was measured by secondary ion mass spectrometry to be in the range of 10(21) cm(-3). The Si-H and Si-H-2 bonds were confirmed by Raman spectroscopy. Next, we applied a-Si:H layers on a medium-doped n-Si(111) substrate (resistivity rho = 6-9 Omega cm), the passivation properties were verified by quasi-steady-state photoconductivity measurement. Finally, the photoresponsivity of 500-nm-thick BaSi2 film capped with 3-nm-thick a-Si:H layers was improved by a factor of 4 compared to those capped with the pure amorphous Si (a-Si).

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  • Application of light trapping structure using Ge dot mask by alkaline etching to heterojunction solar cell

    Atsushi Hombe, Yasuyoshi Kurokawa, Kazuhiro Gotoh, Noritaka Usami

    2018 IEEE 7TH WORLD CONFERENCE ON PHOTOVOLTAIC ENERGY CONVERSION (WCPEC) (A JOINT CONFERENCE OF 45TH IEEE PVSC, 28TH PVSEC & 34TH EU PVSEC)   3097 - 3101   2018年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    Heterojunction solar cells were fabricated with novel light trapping structure formed by selective etching using Ge dots as an etching mask. The light trapping structure has a lot of islands with submicron scale and nanoscale. Etching margin was less than 2 mu m. The light trapping structure was fabricated by changing the parameter of the Ge layer. As a result, the sample fabricated at the Ge coverage of 60 monolayers (MLs) had the largest island structure. The solar cell with the structure with Ge coverage of 60MLs showed high short-circuit current density of 39.7 mA/cm(2). This is because the novel light trapping structure consisted of submicron textures and nanoscale textures and enhanced the light absorption in a wide range.

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  • Development of the Passivation Layer For P-type CuI Thin Film Fabricated by the 2-step Method as the Novel Hole Selective Contact of Silicon Heterojunction Solar Cells

    Min Cui, Kazuhiro Gotoh, Yasuyoshi Kurokawa, Noritaka Usami

    2018 IEEE 7TH WORLD CONFERENCE ON PHOTOVOLTAIC ENERGY CONVERSION (WCPEC) (A JOINT CONFERENCE OF 45TH IEEE PVSC, 28TH PVSEC & 34TH EU PVSEC)   2118 - 2120   2018年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    The passivation of the heterojunction interfaces between the carrier selective contact and the crystalline silicon (cSi) is crucial to achieve high power conversion efficiency in the silicon heterojunction solar cells. We develop a passivation layer applicable to the hole selective contact copper iodide (Cul) fabricated by the 2-step method which includes direct deposition of copper (Cu) on the substrate. The intrinsic hydrogenated amorphous silicon (i-a-Si:H) layer and the intrinsic hydrogenated amorphous silicon oxide (i-a-SiOx:II) layer are stacked on c-Si substrate by the plasma enhanced chemical vapor deposition (PECVD) before Cul fabrication. We demonstrate that the i-aSiO(x):H layer prevents Cu from diffusing into the i-a-Si:H layer and degrading the minority carrier lifetime of the substrate.

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  • Controllable Optical and Electrical Properties of Nb Doped TiO2 Films by RF Sputtering

    Xuemei Cheng, Kazuhiro Gotoh, Takeya Mochizuki, Noritaka Usami

    2018 IEEE 7TH WORLD CONFERENCE ON PHOTOVOLTAIC ENERGY CONVERSION (WCPEC) (A JOINT CONFERENCE OF 45TH IEEE PVSC, 28TH PVSEC & 34TH EU PVSEC)   1986 - 1990   2018年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    RF magnetron sputtered Nb doped titanium oxide (TiO2:Nb) thin film on alkali-free glass substrate is shown to provide good transparency and low resistivity. Both the optical and electrical properties are closely dependent on the deposition parameters as well as the post-annealing process. The impact of deposition power (100-400 W), deposition temperature (25-200 degrees C) and O-2/O-2+Ar flow rate ratio (0-9.09%) on the optical and electrical properties have been studied. A significant improvement of the conductivity of TiO2:Nb thin film is observed after annealing at 600 degrees C over 60min, leading to the decrease of resistivity from 7x10(3) Omega.cm to 2x10(-3) Omega.cm and the transparency over 70% in the visible wavelength. Due to its high work function and the obtained good opto-electrical property, TiO2:Nb has a great potential as an electron selective contact for dopant-free Si solar cells or transparent conductive oxide material.

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  • Boron-doped p-BaSi2/n-Si solar cells formed on textured n-Si(001) with a pyramid structure consisting of {111} facets

    Tianguo Deng, Kazuhiro Gotoh, Ryota Takabe, Zhihao Xu, Suguru Yachi, Yudai Yamashita, Kaoru Toko, Noritaka Usami, Takashi Suemasu

    JOURNAL OF CRYSTAL GROWTH   475   186 - 191   2017年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    BaSi2 films were fabricated on textured Si(001) substrates that consisted of {111} facets using molecular beam epitaxy. The light-trapping effect of these films and their performance when incorporated into solar cells were measured. X-ray diffraction and reflectivity measurements showed that the BaSi2 films were grown epitaxially on the textured Si(001) substrate and confirmed the light-trapping effect. The critical thickness over which BaSi2 relaxes increased from approximately 50 to 100 nm when comparing the BaSi2 films on a flat Si(111) substrate and the textured substrate, respectively. p-BaSi2/n-Si solar cells were fabricated with varying BaSi2 layer thickness and with hole concentrations in the range between 2.0 x 10(18) and 4.6 x 10(18) cm (3). These cells exhibited a maximum energy conversion efficiency of 4.62% with an open-circuit voltage of 0.30 V and a short-circuit current density of 27.6 mA/cm(2) when the p-BaSi2 layer was 75 nm-thick. These results indicated that the use of BaSi2 films on textured Si (001) substrates in solar cells shows great promise. (C) 2017 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jcrysgro.2017.06.017

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  • Fabrication of CuI/a-Si:H/c-Si Structure for Application to Hole-selective Contacts of Heterojunction Si Solar Cells

    Kazuhiro Gotoh, Min Cui, Nguyen Cong Thanh, Koichi Koyama, Isao Takahashi, Yasuyoshi Kurokawa, Hideki Matsumura, Noritaka Usami

    2017 IEEE 44TH PHOTOVOLTAIC SPECIALIST CONFERENCE (PVSC)   1765 - 1768   2017年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    We report on structural and optical properties of copper iodide (CuI) on crystalline Si (c-Si) and properties of the diode with intrinsic type (i-type) hydrogenated amorphous Si (aSi: H) at CuI/c-Si interface. The i-type a-Si: H layer was deposited on n-type c-Si by catalytic chemical vapor deposition (Cat-CVD) prior to deposition of CuI by spin-coating method. Higher rotational speed of 4000 rpm was found to be useful to suppress generation of large particles and absorption by CuI. The effective carrier lifetime was characterized for CuI/a-Si: H/c-Si/a-Si: H/CuI structures and it strongly depended on a-Si: H. The CuI/a-Si: H/cSi diodes showed rectification behavior.

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  • Development of spin-coated copper iodide on silicon for use in hole-selective contacts

    Kazuhiro Gotoh, Min Cui, Isao Takahashi, Yasuyoshi Kurokawa, Noritaka Usami

    7TH INTERNATIONAL CONFERENCE ON SILICON PHOTOVOLTAICS, SILICONPV 2017   124   598 - 603   2017年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:ELSEVIER SCIENCE BV  

    We studied on surface morphology, optical properties and passivation performance of copper iodide (CuI) on crystalline silicon (c-Si) deposited by spin-coating for application to hole-selective contacts to realize high performance and low-cost c-Si solar cells. Absorbance was increased by depositing CuI on c-Si owing to absorption and antireflection effect of Cut From surface images by scanning electron microscope measurements, discontinuous layer was observed for CuI deposited Si. Effective lifetime was characterized for c-Si with ultra-thin oxide covered by CuI both sides by using a microwave photoconductive decay. The lifetime increased from 2 mu s to order of 10 mu s by introducing CuI layer possibly due to large conduction band offset. (C) 2017 The Authors. Published by Elsevier Ltd.

    DOI: 10.1016/j.egypro.2017.09.081

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  • Solar Cells Application of p-type poly-Si Thin Film by Aluminum Induced Crystallization

    Shota Masuda, Kazuhiro Gotoh, Isao Takahashi, Kyotaro Nakamura, Yoshio Ohshita, Noritaka Usami

    2017 IEEE 44TH PHOTOVOLTAIC SPECIALIST CONFERENCE (PVSC)   1794 - 1796   2017年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    We applied aluminum-induced crystallization (AIC) as a technique to realize heavily doped p-type polycrystalline Si layer at low temperature for the rear side of tunnel oxide passivated contact concept solar cell. Systematic temperature variation of AIC revealed that annealing at a temperature slightly lower than the eutectic temperature (577 degrees C) is effective to improve solar cell performance. This is explained by reduced resistivity for low contact resistance while avoiding melting of Al-Si.

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  • Fabrication of strain-compensated heterojunction Ge/Si1-xCx quantum dots solar cells 査読

    K. Gotoh, R. Oshima, T. Yayagaki, T. Sugaya, K. Matsubara, M. Kondo

    32nd EUPVSEC Proceeding   28-31   2016年

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

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  • Strain-compensated Ge/Si1-xCx quantum dots with Si mediating layers grown by molecular beam epitaxy

    Kazuhiro Gotoh, Ryuji Oshima, Takeyoshi Sugaya, Isao Sakata, Koji Matsubara, Michio Kondo

    JOURNAL OF CRYSTAL GROWTH   425   167 - 171   2015年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER  

    We fabricated 20-layer-stacked Ge/Si1-xCx quantum dots (QDs) by solid source molecular beam epitaxy, for the realization of Si-based, strain-compensated Ge QDs. We inserted 2-nm-thick Si mediating layers between the Ge QDs and the Si1-xCx strain-compensating spacer layers (SCLs) and evaluated their influence on the structural and optical properties of the obtained system. High density QDs with a size fluctuation of approximately 14% were successfully maintained independent of the number of stacked layers in the case of QDs with Si mediating layers, while the QD size monotonically increased with a number of stacked layers in the case of QDs without Si mediating layers. The sheet density of QDs with Si mediating layers reached 1.2 x 10(11) cm(-2). A strong photoluminescence (PL) emission with a line-width of 96.7 meV was obtained for the QDs with Si mediating layers. The improvement of the aforementioned properties was caused by both the absence of C bonds at the surface and the improved surface roughness obtained by introducing Si mediating layers. The QD size increased for the 20-layer-stacked Ge/Si QDs samples grown with 10-nm-thick spacer layers, due to the accumulation of internal strains. By contrast, the size distribution of QDs was almost constant for the range of spacer layer thicknesses used in the present work (between 10 am and 40 nm), implying that the tensile-strained Si1-xCx SCLs compensated a certain fraction of the strain field created by the compressive-strained Ge QDs. (C) 2015 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jcrysgro.2015.02.043

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  • Effect of deposition rate on the characteristics of Ge quantum dots on Si (001) substrates

    Kazuhiro Gotoh, Ryuji Oshima, Takeyoshi Sugaya, Isao Sakata, Koji Matsubara, Michio Kondo

    THIN SOLID FILMS   557   80 - 83   2014年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE SA  

    We have studied the effect of the deposition rate on the structural and optical characteristics of five-layer-stacked Ge self-assembled quantum dots (QDs) on a Si (001) substrate grown by molecular beam epitaxy. Ge QDs were formed using a pulse growth technique, which consists of high-rate Ge deposition and an interruption in growth. In this work, the deposition rate was varied from 1.1 angstrom/s to 2.8 angstrom/s. Pyramid-shaped QDs with a monomodal size distribution were obtained at 2.8 angstrom/s, while a bimodal size distribution including pyramid-shaped QDs and multifaceted dome-shaped QDs was observed between 1.1 angstrom/s and 2.2 angstrom/s. As a result, an improved size fluctuation of 11.1% and highest sheet density of 5.6 x 10(10) cm(-2) were achieved for the QD sample grown at 2.8 angstrom/s. As for the optical characteristics, a single photoluminescence (PL) emission line at 0.825eV with a width of 86.1 meV was observed at 12K. Furthermore, we found that the PL emission from the Ge QDs shows type-II emission characteristics, i.e., the shift of the PL peak energy with respect to the PL excitation power (P-exc) was proportional to P-exc(1/3). (c) 2013 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.tsf.2013.10.071

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  • Optical and structural studies of highly uniform Ge quantum dots on Si (001) substrate grown by solid-source molecular beam epitaxy

    Kazuhiro Gotoh, Ryuji Oshima, Takeyoshi Sugaya, Isao Sakata, Koji Matsubara, Michio Kondo

    JOURNAL OF CRYSTAL GROWTH   378   439 - 441   2013年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    We have studied Ge self-assembled quantum dots (QDs) grown by molecular beam epitaxy on Si (001) substrates. We investigated the effect of a pulse growth technique, which involves the combination of a high deposition rate of 2.8 angstrom/s and a 5-s growth interruption (GI) time, on the properties of 20-layer stacked Ge QDs. We found that both the size and size dispersion of the QDs grown using the pulse growth technique were successfully maintained without generating any dislocations even after 20 layers of stacking. Further, a high sheet density of 6.9 x 10(10) cm(-2) and better size dispersion of 12.4% can be achieved. In photoluminescence (PL) measurements, PL emission at 0.833 eV with line width of 71.2 meV was clearly observed at 12 K for 20-layer stacked Ge QDs grown using the pulse growth technique. (c) 2013 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jcrysgro.2012.12.121

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  • Fabrication of type-II self-assembled Ge/Si quantum dots for high efficiency solar cells 査読

    K. Gotoh, R. Oshima, T. Sugaya, I. Sakata, K. Matsubara, M. Kondo

    28th EUPVSEC Proceeding   147-150   2013年

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

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▶ 全件表示

MISC

  • 半導体・磁性体・電池の固/固界面制御と接合・積層技術 第2.4節 査読

    後藤和泰

    S&T出版   59 - 65   2024年6月

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    担当区分:筆頭著者, 責任著者   記述言語:日本語   掲載種別:記事・総説・解説・論説等(商業誌、新聞、ウェブメディア)  

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  • “水素”を使いこなすためのサイエンス ハイドロジェノミクス 査読

    176 - 185   2023年4月

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    担当区分:筆頭著者   記述言語:英語   掲載種別:記事・総説・解説・論説等(商業誌、新聞、ウェブメディア)  

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  • Engineering Heterointerface for High-efficiency Silicon Solar Cells

    Kazuhiro GOTOH, Noritaka USAMI

    Vacuum and Surface Science   66 ( 2 )   86 - 90   2023年2月

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    担当区分:筆頭著者   記述言語:日本語   掲載種別:記事・総説・解説・論説等(学術雑誌)   出版者・発行元:Surface Science Society Japan  

    DOI: 10.1380/vss.66.86

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  • 水素局在化によるヘテロ界面機能の強化 招待 査読

    後藤和泰, 宇佐美徳隆

    セラミックス協会   56 ( 2 )   80 - 83   2021年2月

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    担当区分:筆頭著者   記述言語:日本語   掲載種別:記事・総説・解説・論説等(学術雑誌)  

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講演・口頭発表等

  • TiOx/結晶Siヘテロ構造における電極製膜後のパッシベーション性能の定量的評価の検討

    深谷昌平, 後藤和泰, 松井卓矢, 齋均, 黒川康良, 宇佐美徳隆

    第18回次世代の太陽光発電システムシンポジウム  2021年10月  日本太陽光発電学会

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    開催年月日: 2021年10月

    記述言語:日本語   会議種別:口頭発表(一般)  

    開催地:オンライン  

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  • 水素パッシベーションによるAs-doped n-BaSi2膜の分光感度向上及び第一原理計算を用いた考察

    青貫翔, 山下雄大, Z. Xu, 後藤和泰, 都甲薫, 宇佐美徳隆, D. Migas, 末益宗

    第18回次世代の太陽光発電システムシンポジウム  2021年10月  日本太陽光発電学会

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    開催年月日: 2021年10月

    記述言語:日本語   会議種別:口頭発表(一般)  

    開催地:オンライン  

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  • 真空蒸着法により作製したMg₂Si薄膜の高品質化に向けたface-to-faceアニール効果

    佐藤 海誓, 宮本 聡, 後藤 和泰, 黒川 康良, 伊藤 孝至, 宇佐美 徳隆

    第82回応用物理学会秋季学術講演会  2021年9月  応用物理学会

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    開催年月日: 2021年9月

    記述言語:日本語   会議種別:口頭発表(一般)  

    開催地:オンライン  

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  • シリコンナノ結晶/酸化シリコン複合膜におけるキャリア選択能の水素プラズマ処理温度依存性

    松見優志, 後藤和泰, ビルデ マーカス, 黒川康良, 福谷克之, 宇佐美徳隆

    第82回応用物理学会秋季学術講演会  2021年9月  応用物理学会

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    開催年月日: 2021年9月

    記述言語:日本語   会議種別:口頭発表(一般)  

    開催地:オンライン  

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  • a-Si:H層のPECVD成膜による結晶シリコンへのダメージの評価

    小島遥希, 西原達平, 後藤和泰, 宇佐美徳隆, 原友彦, 大下祥雄, 小椋厚志

    第82回応用物理学会秋季学術講演会  2021年9月  応用物理学会

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    開催年月日: 2021年9月

    記述言語:日本語   会議種別:口頭発表(一般)  

    開催地:オンライン  

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  • ベイズ最適化を援用したシリコン量子ドット積層構造の欠陥低減

    熊谷風雅, 宮川晋輔, 後藤和泰, 沓掛健太朗, 加藤慎也, 宇佐美徳隆, 黒川康良

    第82回応用物理学会秋季学術講演会  2021年9月  応用物理学会

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    開催年月日: 2021年9月

    記述言語:日本語   会議種別:口頭発表(一般)  

    開催地:オンライン  

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  • Face-to-faceアニールを用いて作製したMg₂Si薄膜のラマン散乱解析

    佐藤 海誓, 宮本 聡, 後藤 和泰, 黒川 康良, 伊藤 孝至, 宇佐美 徳隆

    第19回シリサイド系半導体・夏の学校  2021年8月  応用物理学会シリサイド系半導体と関連物質研究会

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    開催年月日: 2021年8月

    記述言語:日本語   会議種別:ポスター発表  

    開催地:オンライン  

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  • 真空蒸着法によるステンレス基板上へのBaSi2薄膜の作製

    陳 嘉坤, 宮本 聡, 後藤 和泰, 黒川 康良, 宇佐美 徳隆

    第19回シリサイド系半導体・夏の学校  2021年8月  応用物理学会シリサイド系半導体と関連物質研究会

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    開催年月日: 2021年8月

    記述言語:日本語   会議種別:ポスター発表  

    開催地:オンライン  

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  • DEVELOPMENT OF SILICON-NANOCRYSTALS-EMBEDDED SILICON OXIDE PASSIVATING CONTACTS FOR USE IN CRYSTALLINE SILICON SOLAR CELLS 招待 国際会議

    K. Gotoh, R. Tsubata, M. Matsumi, M. Wilde, T. Inoue, Y. Kurokawa, K. Fukutani, N. Usami

    Global Photovoltaic Conference 2021 (GPVC 2021)  2021年7月 

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    開催年月日: 2021年7月

    記述言語:英語   会議種別:口頭発表(招待・特別)  

    開催地:Hybrid (Gwangju/virtural)  

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  • Realization of the Cystalline Silicon Solar Cell Using Nanocrystalline Transport Path in Ultra-thin Dielectrics for Reinforced Passivating Contact 国際会議

    R. Tsubata, K. Gotoh, T. Inoue, Y. Kurokawa, N. Usami

    48th IEEE Photovoltaic Specialists Conference  2021年6月 

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    開催年月日: 2021年6月

    記述言語:英語   会議種別:口頭発表(一般)  

    開催地:Online  

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  • 極薄シリコン酸化膜をパッシベーティングコンタクトとして用いた太陽電池の 研究開発動向 招待

    後藤 和泰

    日本太陽光発電学会 次世代太陽電池セル・モジュール分科会 第1回研究会  2021年6月  日本太陽光発電学会

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    開催年月日: 2021年6月

    記述言語:日本語   会議種別:口頭発表(招待・特別)  

    開催地:オンライン  

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  • Improved Performance of Titanium Oxide Electron-Selective Contact by Implementation of Magnesium Interlayer 国際会議

    Yuta Nakagawa, Kazuhiro Gotoh, Yasuyoshi Kurokawa, Noritaka Usami

    11th International Conference on Crystalline Silicon Photovoltaics  2021年4月 

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    開催年月日: 2021年4月

    記述言語:英語   会議種別:ポスター発表  

    開催地:Online  

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  • Application of Bayesian Optimization for Improved Passivation Performance in TiOx/SiOy/c-Si Heterostructure by Hydrogen Plasma Treatment 国際会議

    Shinsuke Miyagawa, Kazuhiro Gotoh, Kentaro Kutsukake, Yasuyoshi Kurokawa, Noritaka Usami

    11th International Conference on Crystalline Silicon Photovoltaics  2021年4月 

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    開催年月日: 2021年4月

    記述言語:英語   会議種別:口頭発表(一般)  

    開催地:Online  

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  • シリコンナノ結晶/酸化シリコンを複合化した導電性パッシベーション膜の太陽電池応用

    津幡亮平, 後藤和泰, 黒川康良, 宇佐美徳隆

    第68回応用物理学会春季学術講演会  2021年3月 

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    開催年月日: 2021年3月

    記述言語:日本語   会議種別:口頭発表(一般)  

    国名:日本国  

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  • ベイズ最適化を援用した高性能パッシベーティングコンタクトの実現 ~TiOx/結晶Siヘテロ構造への適用~

    宮川晋輔, 後藤和泰, 沓掛健太朗, 黒川康良, 宇佐美徳隆

    第68回応用物理学会春季学術講演会  2021年3月 

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    開催年月日: 2021年3月

    記述言語:日本語   会議種別:口頭発表(一般)  

    国名:日本国  

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  • シリコンナノ結晶/酸化シリコン複合膜に対する水素化処理の検討

    松見優志, 後藤和泰, ビルデマーカス, 黒川康良, 福谷克之, 宇佐美徳隆

    第68回応用物理学会春季学術講演会  2021年3月 

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    開催年月日: 2021年3月

    記述言語:日本語   会議種別:口頭発表(一般)  

    国名:日本国  

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  • ベイズ最適化を用いたTiOx/SiOy結晶Siへテロ構造における水素プラズマ処理条件の最適化

    宮川晋輔, 後藤和泰, 沓掛健太朗, 黒川康良, 宇佐美徳隆

    第3回結晶工学×ISYSE合同研究会  2020年12月 

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    開催年月日: 2020年12月

    記述言語:日本語   会議種別:ポスター発表  

    国名:日本国  

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  • 成長速度の二段階制御による真空蒸着BaSi2薄膜の高品質化

    吉野孝政, 後藤和泰, 黒川康良, 宇佐美徳隆

    第3回結晶工学×ISYSE合同研究会  2020年12月 

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    開催年月日: 2020年12月

    記述言語:日本語   会議種別:ポスター発表  

    国名:日本国  

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  • Impact of hydrogen plasma treatment on the passivation performance of TiOx prepared on crystalline silicon by atomic layer deposition 国際会議

    Shinsuke Miyagawa, Kazuhiro Gotoh, Shohei Ogura, Markus Wilde, Yasuyoshi Kurokawa, Katsuyuki Fukutani, Noritaka Usami

    The 30th International Photovoltaic Science and Engineering Conference (PVSEC-30)  2020年11月 

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    開催年月日: 2020年11月

    記述言語:英語   会議種別:口頭発表(一般)  

    国名:大韓民国  

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  • CARBON DIOXIDE/ SILANE GAS FLOW RATE DEPENDENCY ON ELECTRICAL PROPERTIES IN SILICON-NANOCRYSTALS-EMBEDDED SILICON OXIDE PASSIVATING CONTACTS 国際会議

    Ryohei Tsubata, Kazuhiro Gotoh, Yasuyoshi Kurokawa, Noritaka Usami

    The 30th International Photovoltaic Science and Engineering Conference (PVSEC-30)  2020年11月 

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    開催年月日: 2020年11月

    記述言語:英語   会議種別:ポスター発表  

    国名:大韓民国  

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  • DEPENDENCE OF ELECTRICAL PROPERTIES OF STACKED SN-DOPED IN2O3 FILMS ON OXYGEN PARTIAL PRESSURE 国際会議

    Tetsuya Inoue, Kazuhiro Gotoh, Yasuyoshi Kurokawa, Noritaka Usami

    The 30th International Photovoltaic Science and Engineering Conference (PVSEC-30)  2020年11月 

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    開催年月日: 2020年11月

    記述言語:英語   会議種別:ポスター発表  

    国名:大韓民国  

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  • Effect of forming gas annealing on hydrogen content and surface morphology of titanium oxide-coated crystalline silicon heterocontacts 国際会議

    Yuta Nakagawa, Kazuhiro Gotoh, Markus Wilde, Shohei Ogura, Yasuyoshi Kurokawa, Katsuyuki Fukutani, Noritaka Usami

    The 30th International Photovoltaic Science and Engineering Conference (PVSEC-30)  2020年11月 

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    開催年月日: 2020年11月

    記述言語:英語   会議種別:口頭発表(一般)  

    国名:大韓民国  

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  • Improvement of BaSi2 thin film quality by two-step growth rate control of vacuum evaporation 国際会議

    Takamasa Yoshino, Kazuhiro Gotoh, Yasuyoshi Kurokawa, Noritaka Usami

    The 30th International Photovoltaic Science and Engineering Conference (PVSEC-30)  2020年11月 

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    開催年月日: 2020年11月

    記述言語:英語   会議種別:ポスター発表  

    国名:大韓民国  

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  • 光電子ピンセットにより制御されたコロイド結晶化のその場観察

    中川原英亜, 新家寛正, 石川晃平, 後藤和泰, 野澤純, 岡田純平, 宇田聡

    第50回結晶成長国内会議  2020年11月 

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    開催年月日: 2020年11月

    記述言語:日本語   会議種別:口頭発表(一般)  

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  • 積層Sn添加In2O3薄膜における電気的特性の酸素分圧依存性

    井上徹哉, 後藤和泰, 黒川康良, 宇佐美徳隆

    第17回「次世代の太陽光発電システム」シンポジウム  2020年10月 

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    開催年月日: 2020年11月

    記述言語:日本語   会議種別:ポスター発表  

    国名:日本国  

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  • ベイズ最適化を用いたTiOx/SiOy結晶Siへテロ構造における水素プラズマ処理条件の最適化

    宮川晋輔, 後藤和泰, 沓掛健太朗, 黒川康良, 宇佐美徳隆

    第17回「次世代の太陽光発電システム」シンポジウム  2020年10月 

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    開催年月日: 2020年11月

    記述言語:日本語   会議種別:ポスター発表  

    国名:日本国  

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  • 成長速度の二段階制御による真空蒸着BaSi2薄膜の高品質化

    吉野孝政, 後藤和泰, 黒川康良, 宇佐美徳隆

    第17回「次世代の太陽光発電システム」シンポジウム  2020年10月 

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    開催年月日: 2020年11月

    記述言語:日本語   会議種別:ポスター発表  

    国名:日本国  

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  • Mg層を挿入したTiOx/SiOy/Si構造の接合特性のTiOx膜厚依存性

    中川裕太, 後藤和泰, 黒川康良, 宇佐美徳隆

    第17回「次世代の太陽光発電システム」シンポジウム  2020年10月 

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    開催年月日: 2020年11月

    記述言語:日本語   会議種別:ポスター発表  

    国名:日本国  

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  • シリコンナノ結晶/酸化シリコン復合膜における炭酸ガス/シランガス流量比依存性

    津幡亮平, 後藤和泰, 黒川康良, 宇佐美徳隆

    第17回「次世代の太陽光発電システム」シンポジウム  2020年10月 

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    開催年月日: 2020年11月

    記述言語:日本語   会議種別:ポスター発表  

    国名:日本国  

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  • 原子層堆積法で作製した酸化チタンの結晶シリコンに対するパッシベーション効果の発現機構

    後藤 和泰

    日本表面真空学会分科会: SP部会第164回定例研究会  2020年9月 

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    開催年月日: 2020年9月

    記述言語:日本語   会議種別:口頭発表(招待・特別)  

    国名:日本国  

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  • Passivation Mechanism of the High-performance Titanium Oxide Passivating Contacts on Crystalline Silicon Studied by Spectroscopic Ellipsometry 国際会議

    K. Gotoh, H. Miura, A. Shimizu, T. Kurokawa, N. Usami

    2020 International Conference on Solid State Devices and Materials (SSDM 2020)  2020年9月 

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    開催年月日: 2020年9月

    記述言語:英語   会議種別:口頭発表(一般)  

    国名:日本国  

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  • Fabrication of TiOx thin film on Si using solution-based process and its passivation performance 国際会議

    H. Luo, V. H. Nguyen, K. Gotoh, Y. Kurokawa, N. Usami

    2020 International Conference on Solid State Devices and Materials (SSDM 2020)  2020年9月 

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    開催年月日: 2020年9月

    記述言語:英語   会議種別:口頭発表(一般)  

    国名:日本国  

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  • Size effect of silicon nanocrystals on Seebeck coefficient of phosphorus-doped Si nanocrystals/silicon oxide multilayers 国際会議

    H. Kobayashi, S. Kato, M. Kurosawa, K. Gotoh, N. Usami, Y. Kurokawa

    2020 International Conference on Solid State Devices and Materials (SSDM 2020)  2020年9月 

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    開催年月日: 2020年9月

    記述言語:英語   会議種別:口頭発表(一般)  

    国名:日本国  

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  • Mg層挿入によるTiOx/Siヘテロ接合の接合特性の向上

    中川 裕太, 後藤 和泰, 黒川 康良, 宇佐美 徳隆

    第81回応用物理学会秋季学術講演会  2020年9月 

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    開催年月日: 2020年9月

    記述言語:日本語   会議種別:口頭発表(一般)  

    国名:日本国  

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  • ベイズ最適化を用いた酸化チタンパッシベーション膜における水素プラズマ処理条件の最適化

    宮川 晋輔, 後藤 和泰, 沓掛 健太朗, 黒川 康良, 宇佐美 徳隆

    第81回応用物理学会秋季学術講演会  2020年9月 

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    開催年月日: 2020年9月

    記述言語:日本語   会議種別:口頭発表(一般)  

    国名:日本国  

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  • シリコンナノ結晶/酸化シリコンを複合化した導電性パッシベーション膜の検討

    津幡 亮平, 後藤 和泰, 黑川 康良, 宇佐美 徳隆

    第81回応用物理学会秋季学術講演会  2020年9月 

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    開催年月日: 2020年9月

    記述言語:日本語   会議種別:口頭発表(一般)  

    国名:日本国  

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  • Effect of Hydrogen Plasma Treatment on Silicon Quantum Dot Multilalyers Using Amorphous SiOx 国際会議

    R. Akaishi, K. Gotoh, N. Usami, Y. Kurokawa

    37th European PV Solar Eneregy Conference and Exhibition  2020年9月 

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    開催年月日: 2020年9月

    記述言語:英語   会議種別:ポスター発表  

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  • Formation of p-Type BaSi2 Thin Film and its Application to Silicon-Based Heterojunction Solar Cells 国際会議

    Yuki Kimura, Michinobu Fujiwara, Kazuma Takahashi, Yoshihiko Nakagawa, Takamasa Yoshino, Kazuhiro Gotoh, Yasuyoshi Kurokawa, Noritaka Usami

    37th European PV Solar Eneregy Conference and Exhibition  2020年9月 

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    開催年月日: 2020年9月

    記述言語:英語   会議種別:口頭発表(一般)  

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  • Fabrication of silicon-nanocrystals-embedded silicon oxide passivating contacts 国際会議

    Ryohei Tsubata, Kazuhiro Gotoh, Yasuyoshi Kurokawa, Noritaka Usami

    47th IEEE Photovoltaic Specialists Conference (PVSC 47)  2020年6月 

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    開催年月日: 2020年6月

    記述言語:英語   会議種別:ポスター発表  

    国名:アメリカ合衆国  

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  • Work function of indium oxide thin films on p-type hydrogenated amorphous silicon 国際会議

    Masanori Semma, Kazuhiro Gotoh, Yasuyoshi Kurokawa, Noritaka Usami

    47th IEEE Photovoltaic Specialists Conference (PVSC 47)  2020年6月 

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    開催年月日: 2020年6月

    記述言語:英語   会議種別:ポスター発表  

    国名:アメリカ合衆国  

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産業財産権

  • 導電性保護膜および太陽電池

    後藤和泰, 津幡亮平, 宇佐美徳隆

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    出願人:国立大学法人名古屋大学

    出願番号:特願2020-061178  出願日:2020年3月

    出願国:国内  

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受賞

  • イノベイティブPV奨励賞

    2019年7月   日本学術振興会 175委員会  

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  • 第7回研究部共同研究利用・共同研究若手萌芽研究最優秀賞

    2019年5月   東北大学金属材料研究所  

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  • 薄膜太陽電池奨励賞

    2013年11月   薄膜太陽電池セミナー実行委員会  

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  • 土肥賞

    2013年2月   東京工業大学  

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共同研究・競争的資金等の研究

  • ナノ構造と誘電体とを複合した導電性保護膜のキャリア輸送機構の解明

    研究課題/領域番号:24K08243

    2024年4月 - 2027年3月

    制度名:科学研究費助成事業

    研究種目:基盤研究(C)

    提供機関:日本学術振興会

    後藤 和泰

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    配分額:4550000円 ( 直接経費:3500000円 、 間接経費:1050000円 )

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  • 従来にない高効率、低コスト、高耐久性を兼ね備えた太陽電池を実現する要素技術開発

    研究課題/領域番号:20332524

    2020年12月 - 2024年2月

    制度名:クリーンエネルギー分野における革新的技術の国際共同研究開発事業

    提供機関:国立研究開発法人新エネルギー・産業技術総合開発機構

    松井 卓矢

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    担当区分:研究分担者  資金種別:競争的資金

    配分額:26398000円 ( 直接経費:22958000円 、 間接経費:3440000円 )

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  • 超高効率モジュール技術開発/超高効率多段接合モジュール開発

    研究課題/領域番号:P20015

    2020年7月 - 2023年2月

    制度名:太陽光発電主力電源化推進技術開

    提供機関:国立研究開発法人新エネルギー・産業技術総合開発機構

    宇佐美徳隆, 黒川康良, 後藤和泰

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    担当区分:研究分担者  資金種別:競争的資金

    配分額:30000000円 ( 直接経費:2696000円 、 間接経費:3912000円 )

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  • シリコンナノ結晶をキャリア輸送経路に用いた新規導電性保護膜の研究

    研究課題/領域番号:20K15127

    2020年4月 - 2023年3月

    制度名:科学研究費助成事業

    研究種目:若手研究

    提供機関:日本学術振興会

    後藤 和泰

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    担当区分:研究代表者 

    配分額:4160000円 ( 直接経費:3200000円 、 間接経費:960000円 )

    本研究では、酸化シリコン中のシリコンナノ結晶をキャリア輸送経路とした新規導電性保護膜の開発を目指す。酸化シリコンはシリコンに対して良好な保護膜として機能するが、絶縁性を示すためキャリア輸送に不利である。そこで、申請者はキャリア輸送経路としてシリコン酸化膜中にシリコンナノ結晶を応用することに着目した。本研究では、シリコンナノ結晶を含むシリコン酸化膜の構造特性、光学的特性および電気的特性の相関を調査することにより、シリコンナノ結晶を用いた極薄シリコン酸化膜のキャリアの輸送に関する基礎研究を行い、保護性能と導電性を両立した新規導電性保護膜の開発を志向する。

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  • 光パスツールピンセットを駆使したカイラル結晶相転移科学の創成

    研究課題/領域番号:20H02686

    2020年4月 - 2023年3月

    制度名:科学研究費助成事業

    研究種目:基盤研究(B)

    提供機関:日本学術振興会

    新家 寛正

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    担当区分:研究分担者  資金種別:競争的資金

    配分額:17810000円 ( 直接経費:13700000円 、 間接経費:4110000円 )

    本研究では、電磁場のカイラリティの尺度を表す保存量である「Optical Chirality」の勾配を起源とする光学力による鏡像体選択的な光学捕捉技術により、水溶液中の分子クラスターを鏡像体選択的に濃集し鏡像対称性の破れを伴う結晶核形成を人為的に誘起する。誘電体ナノ構造体のMie共振により発生するOptical Chiralityの増強された近接場を鏡像対称性の破れた外場とみなし、これを印可することで本来熱力学的に等価な結晶鏡像異性体を熱力学的に区別する。これにより、相転移を記述する上で基本的な量である化学ポテンシャルにカイラリティの概念を導入する。

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  • 酸化チタン薄膜と結晶シリコンとの界面における未結合手不活化における水素機 能の解明

    研究課題/領域番号:C047

    2019年5月 - 2021年3月

    制度名:MALT共同利用

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  • シリコンナノドットを用いた新規導電性保護膜の開発

    研究課題/領域番号:19K21110

    2019年4月 - 2020年3月

    制度名:科学研究費助成事業

    研究種目:研究活動スタート支援

    提供機関:日本学術振興会

    後藤 和泰

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    担当区分:研究代表者 

    配分額:2990000円 ( 直接経費:2300000円 、 間接経費:690000円 )

    本研究では、酸化シリコン中のシリコンナノドットをキャリア輸送経路とした新規保護膜の開発を目指す。申請者は、キャリア輸送経路としてシリコン酸化膜中のシリコンナノドットを応用することに着目した。申請者の研究グループでは、シリコン酸化膜中にシリコンナノドットを形成する技術を有しており、シリコンナノドットのサイズなどの構造制御が可能である。本研究では、シリコン酸化膜中にシリコンナノドットを形成し、形成時のパラメータと構造及び電気的特性の相関を調査する。本研究により、本来絶縁性の保護膜であるシリコン酸化膜にキャリア輸送経路を形成して制御を行い、新規導電性保護膜の基盤を構築することが期待できる。
    本研究は、酸化シリコン中のシリコンナノ結晶をキャリア輸送経路とした新規導電性保護膜の開発を目指して実施された。試料は、シリコンリッチのアモルファス酸化シリコンを酸素リッチのアモルファス酸化シリコンで挟み込む順番でシリコン基板上に3層構造を製膜し、熱処理を行うことにより酸化シリコン中にシリコンのナノ結晶を形成した。
    酸素リッチのアモルファス酸化シリコンを採用することにより、酸化シリコン中にシリコンのナノ結晶が形成し、保護性能を示すことを確認した。さらに、酸化シリコン中のシリコンナノ結晶が電気伝導を担っていることを示唆し、保護性能と電気伝導を両立する導電性保護膜の開発が期待できる結果が得られた。
    シリコンは、現在の社会を成り立たせる材料の一つである。シリコン表面に対する良好な保護性能を示す保護膜は、通常絶縁性の材料であり電気伝導との両立が困難である。本研究では、良好な保護特性と電気伝導性を両立する導電性保護膜の開発を志向した。その結果、シリコン酸化膜中のナノ結晶シリコンの比率が大きくなるほど、保護性能が低下する一方、電気伝導が向上する結果を得た。このことは、保護性能と電気伝導を制御することが可能となることを意味している。開発した導電性保護膜は、太陽電池への応用だけでなく、シリコン基板と様々な材料との接合材として利用するなどの展開が可能であり、高い社会的意義が期待できる成果が得られた。

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  • 結晶シリコン界面の未結合手不活性化における水素機能の解明

    研究課題/領域番号:18K0093

    2018年4月 - 2019年3月

    制度名:平成30年度東北大学金属材料研究所共同研究

    提供機関:東北大学金属材料研究所

    後藤 和泰

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    資金種別:競争的資金

    配分額:300000円 ( 直接経費:300000円 )

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▶ 全件表示

 

担当経験のある授業科目(researchmap)

  • ナノテクノロジー特論

    2024年

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  • 物理工学II

    2023年
    -
    2024年

     詳細を見る

  • 電気回路演習I

    2023年
    -
    2024年

     詳細を見る

  • 総合技術科学演習

    2023年
    -
    2024年

     詳細を見る

  • 物質創製工学セミナー2A

    2020年
    -
    2023年
    機関名:名古屋大学

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    科目区分:大学院専門科目 

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  • 物質創製工学セミナー2D

    2020年
    -
    2023年
    機関名:名古屋大学

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    科目区分:大学院専門科目 

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  • 物質創製工学セミナー2E

    2020年
    -
    2023年
    機関名:名古屋大学

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    科目区分:大学院専門科目 

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  • 物質創製工学セミナー2B

    2020年
    -
    2023年
    機関名:名古屋大学

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    科目区分:大学院専門科目 

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  • 物質創製工学セミナー2C

    2020年
    -
    2023年
    機関名:名古屋大学

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    科目区分:大学院専門科目 

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  • 物質創製工学セミナー1D

    2020年
    -
    2023年
    機関名:名古屋大学

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    科目区分:大学院専門科目 

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  • 物質創製工学特別実験及び演習2

    2020年
    -
    2023年
    機関名:名古屋大学

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    科目区分:大学院専門科目 

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  • 物質創製工学セミナー1B

    2020年
    -
    2023年
    機関名:名古屋大学

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    科目区分:大学院教養科目 

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  • 物質創製工学セミナー1A

    2020年
    -
    2023年
    機関名:名古屋大学

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    科目区分:大学院専門科目 

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  • 物質創製工学セミナー1C

    2020年
    -
    2023年
    機関名:名古屋大学

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    科目区分:大学院専門科目 

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  • 学生実験2

    2020年
    -
    2023年
    機関名:名古屋大学

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    科目区分:学部専門科目 

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  • 卒業研究B

    2020年
    -
    2023年
    機関名:名古屋大学

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    科目区分:学部教養科目 

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  • 物質創製工学特別実験及び演習1

    2020年
    -
    2022年
    機関名:名古屋大学

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    科目区分:大学院専門科目 

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  • 学生実験1

    2020年
    -
    2022年
    機関名:名古屋大学

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    科目区分:学部専門科目 

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  • 卒業研究A

    2020年
    -
    2022年
    機関名:名古屋大学

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    科目区分:学部専門科目 

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  • マテリアル工学概論

    2019年
    -
    2022年
    機関名:名古屋大学

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    科目区分:学部専門科目 

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  • 材料工学実験及び演習2

    2018年
    機関名:名古屋大学

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    科目区分:学部専門科目 

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  • 材料工学実験及び演習1

    2018年
    機関名:名古屋大学

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    科目区分:学部専門科目 

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担当経験のある授業科目

  • 学問の扉 知と方法の最前線

    2024年
    -
    現在
    機関名:新潟大学

  • 電子材料分析評価法特論

    2024年
    -
    現在
    機関名:新潟大学

  • ナノテクノロジー工学特論

    2024年
    -
    現在
    機関名:新潟大学

  • 電気回路I

    2023年
    -
    現在
    機関名:新潟大学

  • 総合技術科学演習

    2023年
    -
    現在
    機関名:新潟大学

  • 総合技術科学演習

    2023年
    -
    現在
    機関名:新潟大学

  • 工学リテラシー入門(情報電子分野)

    2023年
    -
    現在
    機関名:新潟大学

  • 電気回路演習I

    2023年
    -
    現在
    機関名:新潟大学

  • 物理工学II

    2023年
    -
    現在
    機関名:新潟大学

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社会貢献活動

  • 第16回再生可能エネルギー世界展示会&フォーラム

    役割:出演, 企画

    再生可能エネルギー協議会  2022年1月

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  • 名古屋大学工学部テクノサイエンスセミナー(TSS)

    役割:企画

    2019年8月

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  • PVJapan 2019

    役割:情報提供

    2019年7月

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    対象: 研究者, 社会人・一般, 学術団体, 市民団体, 行政機関

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  • PV Japan2018

    役割:情報提供

    2018年6月

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  • PV Japan2017

    役割:情報提供

    2017年7月

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  • PV Japan2016

    役割:情報提供

    2016年6月 - 2016年7月

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メディア報道

  • 東北大・新潟大・名大・阪大・埼玉大、誘電体メタ表面のナノ領域で発生する光が結晶のキラリティ制御に有効であることを実証 新聞・雑誌

    東北大学、新潟大学、名古屋大学、大阪大学、埼玉大学  日本経済新聞  2024年2月

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    執筆者:本人以外 

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  • 結晶シリコン太陽電池の高性能化を実現、名古屋大学が新材料 インターネットメディア

    スマートジャパン  スマートジャパン  2019年1月

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  • 名大、シリコン太陽電池で新材料、高効率化に期待 インターネットメディア

    日経XTECH  日経XTECH  2019年1月

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  • 太陽電池の変換効率、酸化チタンで向上へ 新聞・雑誌

    日経新聞  日経新聞  2019年1月

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  • 太陽光発電の普及に期待!~太陽電池の高性能化に有用な新材料の開発~

    名古屋大学  2018年12月

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    執筆者:本人 

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学術貢献活動

  • 第18回次世代の太陽光発電システムシンポジウム 座長

    役割:パネル司会・セッションチェア等

    日本太陽光発電学会  2021年10月

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    種別:大会・シンポジウム等 

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  • International Conference on Solid State Devices and Materials 2021 座長 国際学術貢献

    役割:パネル司会・セッションチェア等

    2021年9月

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    種別:学会・研究会等 

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  • 第17回次世代の太陽光発電システムシンポジウム実行委員会Web担当

    役割:企画立案・運営等

    日本太陽光発電学会  2020年10月

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    種別:大会・シンポジウム等 

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  • 応用物理学会若手チャプター 太陽光エネルギー変換機能材料・デバイス開発研究会

    役割:企画立案・運営等

    2018年1月 - 現在

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    種別:学会・研究会等 

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