Faculty Profiles - KUROKAWA Yasuyoshi

Papers - KUROKAWA Yasuyoshi

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Bayesian optimization of hydrogen plasma treatment in silicon quantum dot multilayer and application to solar cells Reviewed International journal

Fuga Kumagai, Kazuhiro Gotoh, Satoru Miyamoto, Shinya Kato, Kentaro Kutsukake, Noritaka Usami, Yasuyoshi Kurokawa

Nanoscale Research Letters Vol. 18 ( 1 ) page： 43 2023.3

Thermoelectric properties of Mg2Si thin films prepared by thermal evaporation of Mg and face-to-face annealing Reviewed International journal

Y. Kurokawa, K. Sato, K. Shibata, S. Kato, S. Miyamoto, K. Gotoh, T. Itoh, N. Usami

Materials Science in Semiconductor Processing Vol. 163 page： 107552 2023.8

Preparation and thermoelectric characterization of boron-doped Si nanocrystals/silicon oxide multilayers Reviewed International journal

Keisuke Shibata, Shinya Kato, Masashi Kurosawa, Kazuhiro Gotoh, Satoru Miyamoto, Noritaka Usami, Yasuyoshi Kurokawa

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 62 ( SC ) page： SC1074 2023.2

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

APPLIED PHYSICS EXPRESS Vol. 14 ( 2 ) page： 025503 2021.2

Preparation and thermoelectric characterization of phosphorus-doped Si nanocrystals/silicon oxide multilayers Reviewed International journal

Kobayashi Hisayoshi, Akaishi Ryushiro, Kato Shinya, Kurosawa Masashi, Usami Noritaka, Kurokawa Yasuyoshi

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 59 ( SG ) page： SGGF09 2020.4

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

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

Nanoscale Research Letters Vol. 15 ( 1 ) page： 39 2020

Local Structure of High Performance TiO <inf>x</inf> Electron-Selective Contact Revealed by Electron Energy Loss Spectroscopy Reviewed International journal

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

Advanced Materials Interfaces Vol. 6 ( 3 ) page： 1801645 2019.2

Bandgap tuning of silicon nanowire arrays for application to all-silicon tandem solar cells Reviewed International journal

Y. Kurokawa, M. Yano, S. Miyajima, and A. Yamada

Jpn. J. Appl. Phys. Vol. 56 page： 04CS03 2017.2

Photoluminescence from silicon quantum dots in Si quantum dots/amorphous SiC superlattice Reviewed International journal

Kurokawa Yasuyoshi, Tomita Shigeki, Miyajima Shinsuke, Yamada Akira, Konagai Makoto

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 46 ( 33-35 ) page： L833 - L835 2007.9

Preparation of nanocrystalline silicon in amorphous silicon carbide matrix Reviewed International journal

Kurokawa Yasuyoshi, Miyajima Shinsuke, Yamada Akira, Konagai Makoto

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 45 ( 37-41 ) page： L1064 - L1066 2006.10

Improvement of nano-texture uniformity formed on crystalline silicon surface by anisotropic alkaline etching for perovskite/silicon tandem solar cells Reviewed

Hiroto Yamaguchi, Yasuyoshi Kurokawa, Shohei Fukaya, Shinya KATO, Noritaka Usami

2025.3

Fabrication of Tilted Mg2Si/Ni Multilayer Composite Modules Using Polylactic Acid Resin Molds and Evaluation of the Thermoelectric Power Generation Performance Invited Reviewed

Tomohiro Kusumoto, Yasuyoshi Kurokawa, Noritaka Usami, Takashi Itoh

J. Jpn. Soc. Powder Powder Metallurgy Vol. 72 ( Supplement ) page： S1269 - S1273 2025.3

Suppression of film blistering in silicon nano-crystals/silicon oxide composite layer by insertion of intrinsic hydrogenated amorphous silicon layer Reviewed

Kazushi Mizutani, Kazuhiro Gotoh, Tomihisa Tachibana, Yasuyoshi Kurokawa, Noritaka Usami

2025.3

Development of Porous Silicon Nanowires with Conductive Paths and Large Specific Surface Area for Application to Lithium-Ion Batteries Reviewed International journal

Shinya Kato, Habin Li, Yosuke Ishii, Yasuyoshi Kurokawa, Tetsuo Soga

ECS Meeting Abstracts Vol. MA2024-02 page： 945 2024.11

Improvement for Passivation Performance of TiOx/SiOy/c-Si Heterostructures by Capping with Atomic-Layer-Deposited Nb Doped TiOx Layer Reviewed International journal

Shohei Fukaya, Kazuhiro Gotoh, Yasuyoshi Kurokawa, Noritaka Usami

Proc. 52nd IEEE Photovoltaic Specialists Conference page： 417 - 419 2024.11

Enhancement of Near-infrared Light Absorption by Nanoimprinted Light Trapping Structure Implemented into Si Heterojunction Solar Cells Reviewed International journal

Yasuyoshi Kurokawa, Yoshiko Iseki, Kazuhiro Gotoh, Satoru Miyamoto, Ryo Ozaki, Kyotaro Nakamura, Yoshio Ohshita, Noritaka Usami

Proc. 52nd IEEE Photovoltaic Specialists Conference page： 39 - 41 2024.11

Fabrication of Planar Thermoelectric Generators using Phosphorus-doped Silicon Nanocrystals/Amorphous Silicon Composite Films Reviewed International journal

Yasuyoshi Kurokawa, Keisuke Shibata, Shinya Kato, Masashi Kurosawa, Satoru Miyamoto, Takashi Itoh, Noritaka Usami

Ext. Abstr. 2024 International Conference on Solid State Devices and Materals page： 283 - 284 2024.9

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

Matsumi, M; Gotoh, K; Wilde, M; Kurokawa, Y; Fukutani, K; Usami, N

NANOTECHNOLOGY Vol. 35 ( 10 ) 2024.3

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

We investigate the effect of hydrogen passivation of dangling bonds in silicon oxide passivating contacts with embedded silicon nanocrystals (NAnocrystalline Transport path in Ultra-thin dielectrics for REinforced passivation contact, NATURE contact). We first investigated the differences in electrical properties of the samples after hydrogen gas annealing and hydrogen plasma treatment (HPT). The results show that the NATURE contact was efficiently passivated by hydrogen after HPT owing to the introduction of hydrogen radicals into the structure. Furthermore, we examined the dependence of process parameters such as HPT temperature, duration, and H2 pressure, on the electrical properties and hydrogen depth profiles. As a result, HPT at 500 °C, 15 min, and 0.5 Torr resulted in a large amount of hydrogen inside the NATURE contact and the highest implied open-circuit voltage of 724 mV. Contact resistivity and surface roughness hardly increased when HPT was performed under the optimized condition, which only improved the passivation performance without deteriorating the electron transport properties of the NATURE contact.

DOI： 10.1088/1361-6528/ad115d

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

Wang, HT; Kurokawa, Y; Zhang, JH; Gotoh, K; Liu, X; Miyamoto, S; Usami, N

APPLIED PHYSICS EXPRESS Vol. 17 ( 1 ) 2024.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Applied Physics Express

Wearable energy harvesters (WEHs) have garnered significant attention recently due to their promising capabilities in powering wearable devices. In this research, we present a core-shell yarn-structured triboelectric nanogenerator (CY-TENG) that operates in two modes: the single-electrode TENG (SE-TENG) and the droplet-based electricity generator. This design facilitates energy harvesting from both waterdrops and biomechanics. The CY-TENG is fabricated using fluorinated ethylene propylene ultrafine heat-shrink tubes combined with stainless-steel yarns, ensuring its flexibility, durability, and weavability. Such attributes underscore its potential as a dual-function WEH.

DOI： 10.35848/1882-0786/ad1f06

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Influence of Insertion Position of a LiF Buffer Layer on Passivation Performance of Crystalline Si/SiOy/TiOx/Al Heterostructures Reviewed International journal

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

Proc. 50th IEEE Photovoltaic Specialists Conference page： 1 - 3 2023.12

Numerical Simulation Study for Analysis of Hydrogenated Amorphous Silicon/Crystalline Silicon Heterostructure by Reactive Molecular Dynamics Method Reviewed International journal

Proc. 50th IEEE Photovoltaic Specialists Conference page： 1 - 3 2023.12

Free-Standing Electrode and Fixed Surface Tiny Electrode Implemented Tiboelectric Nanogenerator with High Instantaneous Current Reviewed

Wang, HT; Kurokawa, Y; Wang, J; Cai, WT; Zhang, JH; Kato, S; Usami, N

SMALL page： e2308531 2023.12

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

Conventional triboelectric nanogenerators (TENGs) face challenges pertaining to low output current density at low working frequencies and high internal impedance. While strategies, such as surface modification to enhance surface charge density, permittivity regulation of materials, and circuit management, have partially mitigated these issues. However, they have also resulted in increased complexity in the fabrication process. Therefore, there is an urgent demand for a universal and simplified approach to address these challenges. To fulfill this need, this work presents a free-standing electrode and fixed surface tiny electrode implemented triboelectric nanogenerator (FFI-TENG). It is fabricated by a straightforward yet effective method: introducing a tiny electrode onto the surface of the tribo-negative material. This approach yields substantial enhancements in performance, notably a more than tenfold increase in output current density, a reduction in effective working frequencies, and a decrease in matching resistance as compared to vertical contact-separation TENGs (CS-TENGs) or single-electrode TENGs (SE-TENGs). Simultaneously, a comprehensive examination and proposition regarding the operational mechanism of FFI-TENG, highlighting its extensive applicability are also offered. Significantly, FFI-TENG excels in mechanical energy harvesting even under ultra-low working frequencies (0.1 Hz), outperforming similar contact-separation models. This innovation positions it as a practical and efficient solution for the development of low-entropy energy harvesters.

DOI： 10.1002/smll.202308531

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The effect of room-temperature plastic deformation in darkness on the photoluminescence properties of ZnS Reviewed

Ogura, Y; Nakamura, A; Kameyama, T; Kurokawa, Y; Tochigi, E; Shibata, N; Torimoto, T; Hoshino, S; Yokoi, T; Matsunaga, K

JOURNAL OF THE AMERICAN CERAMIC SOCIETY Vol. 107 ( 4 ) page： 2040 - 2047 2023.11

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of the American Ceramic Society

Inorganic semiconductors have been considered to be brittle at room temperature generally, but recently zinc sulfide (ZnS), a II–VI compound semiconductor, was found to exhibit extraordinarily large plasticity even at room temperature if it was deformed in darkness. Room-temperature plastic deformation can achieve high density of glide dislocations in the crystal without significantly changing the point defect structure, and these dislocations themselves have a potential to provide unique functional properties different from those of the bulk. In this study, therefore, undoped ZnS crystals were plastically deformed at room temperature in darkness to generate only a large number of dislocations, and the changes in luminescence properties resulting from this process were investigated for the first time. As a result, we found that ZnS deformed in darkness exhibits characteristic photoluminescence and persistent luminescence emissions with a visible green color. SEM-CL analyses also identified the emissions from the dislocations. Theoretical calculations indicated that individual dislocations in ZnS have the ability to trap photo-excited carriers. Such changes in luminescence properties due to room temperature plastic deformation in darkness can be considered to originate from dislocations rather than point defects. In other words, the dislocations themselves serve as the significant recombination centers, realizing visible light emission.

DOI： 10.1111/jace.19564

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

M. Matsumi, K. Gotoh, M. Wilde, Y. Kurokawa, K. Fukutani and N. Usami

Solar Energy Materials and Solar Cells Vol. 262 page： 112538 2023.10

Nanoscale Size Control of Si Pyramid Texture for Perovskite/Si Tandem Solar Cells Enabling Solution-Based Perovskite Top-Cell Fabrication and Improved Si Bottom-Cell Response Reviewed

Li, YQ; Sai, H; Mcdonald, C; Xu, ZH; Kurokawa, Y; Usami, N; Matsui, T

ADVANCED MATERIALS INTERFACES Vol. 10 ( 35 ) 2023.9

Language：English Publishing type：Research paper (scientific journal) Publisher：Advanced Materials Interfaces

A monolithic perovskite/silicon tandem solar cell architecture is employed to surpass the single-junction efficiency limit. Recently, there is an increasing need for the double-sided textures in the Si bottom cell to be compatible with the solution-processed perovskite top cell from an industrial perspective. Herein, a silver-assisted alkaline etching method is applied to fabricate nanoscale Si pyramid textures, and the influence of varying pyramid size (400–900 nm) on the interface morphology and the performance of perovskite/Si tandem cells is investigated. It is demonstrated that electrical shunting starts to increase, and the open-circuit voltage (VOC) decreases when the texture size exceeds the perovskite thickness (~500nm) due to the non-uniform top-cell formation on a rough Si surface. However, when the texture size is reduced to 400–500 nm, all spin-coated perovskite top-cell component layers exhibit an even form over the nanopyramid Si, resulting in a high VOC and an enhanced Si bottom cell current (≈1.0 mA cm−2) due to the suppressed reflectance at the top/bottom cell interface without using optical couplers. The double-sided nanopyramid Si texture offers opportunities to increase tandem cell efficiency while reducing its production cost compared with the commonly used single-sided textured Si.

DOI： 10.1002/admi.202300504

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Impact of B<inf>2</inf>H<inf>6</inf>plasma treatment on contact resistivity in silicon heterojunction solar cells Reviewed

Gotoh K., Ozaki R., Morimura M., Tanaka A., Iseki Y., Nakamura K., Muramatsu K., Kurokawa Y., Ohshita Y., Usami N.

Japanese Journal of Applied Physics Vol. 62 ( SK ) 2023.8

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

We investigated the effect of the B2H6 plasma treatment on p-type hydrogenated amorphous silicon (p-a-Si:H) surfaces for high-performance silicon heterojunction (SHJ) solar cells. Secondary ion mass spectroscopy measurements revealed that the boron concentration at the p-a-Si:H surface is increased by employing the B2H6 plasma treatment. Furthermore, specific contact resistance is decreased by about one-third after the B2H6 plasma treatment. No degradation of passivation performance is induced by the B2H6 plasma treatment. The power conversion efficiency of the SHJ solar cells with the B2H6 plasma treatment is improved by the increase in fill factor (FF) due to decreased series resistance and increased shunt resistance. From numerical simulations, the upward band bending is enhanced at the heterointerface between transparent conductive oxide (TCO) and p-a-Si:H by the B2H6 plasma treatment, which is responsible for the improved FF owing to facilitated tunneling holes from c-Si to p-a-Si:H layers and the TCO/p-a-Si:H heterointerface.

DOI： 10.35848/1347-4065/acc953

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

Fukaya S., Gotoh K., Matsui T., Sai H., Kurokawa Y., Usami N.

Japanese Journal of Applied Physics Vol. 62 ( SK ) 2023.8

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

The degradation of surface passivation performance by metallization is a challenge in realizing highly efficient crystalline Si solar cells that use novel carrier-selective contacts. Here, we report on a simple method to study the effect of metallization on passivation of titanium oxide (TiOx)/Si heterostructures. We investigated the relationship between the implied open-circuit voltage (iV OC) and the photoluminescence (PL) intensity imaging of solar cell precursors before metallization. Based on the relationship obtained, the change of the iV OC before and after metallization on the TiOx was evaluated quantitatively. The results showed that the iV OC predicted by the PL measurement decreases by 23-104 mV after metal deposition and shows a good agreement with the measured V OC in the finished solar cells. These results demonstrate that the iV OC evaluation by PL measurement provides a good prediction of the V OC after metallization, which is useful in analyzing the passivation degradation induced by metallization.

DOI： 10.35848/1347-4065/acc813

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Fabrication of light trapping structures specialized for near-infrared light by nanoimprinting for the application to thin crystalline silicon solar cells Reviewed

Kimata Yuto, Gotoh Kazuhiro, Miyamoto Satoru, Kato Shinya, Kurokawa Yasuyoshi, Usami Noritaka

DISCOVER NANO Vol. 18 ( 1 ) page： 72 2023.5

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

Vehicle-integrated photovoltaics (VIPV) are gaining attention to realize a decarbonized society in the future, and the specifications for solar cells used in VIPV are predicated on a low cost, high efficiency, and the ability to be applied to curved surfaces. One way to meet these requirements is to make the silicon substrate thinner. However, thinner substrates result in lower near-infrared light absorption and lower efficiency. To increase light absorption, light trapping structures (LTSs) can be implemented. However, conventional alkali etched pyramid textures are not specialized for near-infrared light and are insufficient to improve near-infrared light absorption. Therefore, in this study, as an alternative to alkaline etching, we employed a nanoimprinting method that can easily fabricate submicron-sized LTSs on solar cells over a large area. In addition, as a master mold fabrication method with submicron-sized patterns, silica colloidal lithography was adopted. As a result, by controlling silica coverage, diameter of silica particles (D), and etching time (t et), the density, height, and size of LTSs could be controlled. At the silica coverage of 40%, D = 800 nm, and t et = 5 min, the reduction of reflectance below 65% at 1100 nm and the theoretical short-circuit current gain of 1.55 mA/cm2 was achieved.

DOI： 10.1186/s11671-023-03840-6

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

Japanese Journal of Applied Physics Vol. 62 ( SC ) page： SC1032 2023.1

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

DOI： 10.35848/1347-4065/acaca7

Study on the Etching Characteristics and Thermal Conductivity of Porous Silicon Nanowire Arrays Using Highly Doped Silicon Reviewed

Li Haibin, Kato Shinya, Kurokawa Yasuyoshi, Soga Tetsuo

e-Journal of Surface Science and Nanotechnology Vol. advpub ( 0 ) 2022.12

Language：English Publishing type：Research paper (scientific journal) Publisher：The Japan Society of Vacuum and Surface Science

Silicon nanowires (SiNWs) fabricated by metal-assisted chemical etching (MACE) of highly doped silicon are promising thermoelectric materials because of their high conductivity and porosity. However, it is difficult to fabricate long SiNWs using highly doped silicon with doping concentrations higher than 1019 cm−3. In this study, we fabricated SiNWs up to 44 μm in length using highly doped silicon with a doping concentration of 1020 cm−3, analyzed the etching characteristics in SiNWs length and the morphology, and investigated the thermal conductivity. The phenomenon of continuous loss of SiNWs was found, which is a unique phenomenon indicating the presence of loss SiNWs throughout the whole etching process and difficulty of forming long SiNWs with highly doped silicon. On the other hand, the thermal conductivity results showed that the lowest thermal conductivity of the samples reached 2.98 W m−1 K−1, and the mean diameters of pores in these samples were 5−10 nm. Thus, the SiNWs using highly doped silicon is a potential material for thermoelectric device.

DOI： 10.1380/ejssnt.2023-006

CiNii Research

A novel self-separating silicon nanowire thin film and application in lithium-ion batteries Reviewed

Li H., Kato S., Ishii Y., Kurokawa Y., Soga T.

Nano Express Vol. 3 ( 4 ) 2022.12

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

Nano silicon structures are important materials for modern electronic devices and have been widely researched with regard to photoelectricity, thermoelectricity, and lithium-ion batteries. However, since the nano silicon structures fabricated by conventional methods cannot be separated from silicon substrates, reuse of the substrate is restricted. Here, we propose a simple fabrication method to separate the nano silicon structures from the silicon substrates, which allows the reuse of the substrates. The fabrication was processed at room temperature, which allows large-area fabrication and is not restricted by the substrate thickness. Honeycomb structures of different length scales observed on both the nano silicon structure and the substrate suggest that the separation occurred due to the amplification of the silicon crystal defects. The nano silicon structures comprised porous silicon with an excellent specific surface area of 480 m2 g−1 and a mean pore diameter of 5.7 nm. Moreover, the nano silicon structures show good potential as anode materials for lithium-ion batteries wherein the measured reversible capacity was 1,966 mAh g−1 after 100 cycles. Based on the proposed method and morphological characteristics, the fabricated nano silicon structures can be considered a low-cost material with suitable applications in the energy field.

DOI： 10.1088/2632-959X/acb807

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Performance enhancement of droplet-based electricity generator using a CYTOP intermediate layer Reviewed International journal

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

Ext. Abstr. 2022 International Conference on Solid State Devices and Materals page： 145 - 146 2022.9

Preparation and thermoelectric characterization of boron-doped silicon nanocrystals/silicon oxide multilayers Reviewed International journal

Keisuke Shibata, Shinya Kato, Masashi Kurosawa, Kazuhiro Gotoh, Satoru Miyamoto, Noritaka Usami, Yasuyoshi Kurokawa

Ext. Abstr. 2022 International Conference on Solid State Devices and Materals page： 147 - 148 2022.9

Nanopyramid Texture Formation by One-Step Ag-Assisted Solution Process for High-Efficiency Monocrystalline Si Solar Cells Reviewed

Li Y., Sai H., Matsui T., Xu Z., Nguyen V.H., Kurokawa Y., Usami N.

Solar RRL 2022.9

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

In monocrystalline Si solar cells, pyramidal surface textures with the size of a few micrometers (micropyramids) are commonly applied for light in-coupling and trapping. Recently, there is a growing need to reduce the size of pyramids below 1 μm. Herein, an original method to fabricate nanometer-sized pyramids (nanopyramids) featuring an average size of ≈500 nm or even smaller by using a simple one-step Ag-assisted solution process is proposed. The texture size can be controlled by the concentration of AgNO3 in the alkaline etching solution where the generated Ag nanoparticles act as an etching mask as well as promoting the detachment of H2 bubbles from the reacting Si surface. This process enables the formation of uniformly distributed Si nanopyramids with a lower reflectance below 10% and a smaller etching margin less than 1.7 μm compared with the conventional micropyramids. Silicon heterojunction solar cells employing Si nanopyramids outperform those with the conventional micropyramids owing to the reduced optical reflectance while preserving excellent surface passivation and carrier transport properties. These results demonstrate the advantages of our method and the high potential of Si nanopyramids for various applications such as thin crystalline Si solar cells and perovskite/Si tandem solar cells.

DOI： 10.1002/solr.202200707

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

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

Thin Solid Films Vol. 764 page： 139597 2022.9

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

DOI： 10.1016/j.tsf.2022.139597

Enhancement of reflectance reduction of solar cells by a silicon nanoparticle layer on a textured silicon substrate Reviewed

Shinya Kato, Yasuhoshi Kurakawa, Tetsuo Soga

Results in Optics Vol. 9 page： 100296 2022.9

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

DOI： 10.1016/j.rio.2022.100296

Fabrication of Silicon Heterojunction Solar Cells with Light Trapping Structures Specialized for Near-Infrared Light by Nanoimprinting Reviewed International journal

Y. Kimata, K. Gotoh, S. Miyamoto, Y. Kurokawa, N. Usami

Proc. 8th World Conference on Photovoltaic Energy Conversion page： 230 - 233 2022.9

Improvement of Passivation Performance of Silicon Nanocrystal/Silicon Oxide Compound Layer by Hydrogen Plasma Treatment Reviewed International journal

M. Matsumi, K. Gotoh, M. Wilde, Y. Kurokawa, K. Fukutani, N. Usami

Proc. 8th World Conference on Photovoltaic Energy Conversion page： 402 - 405 2022.9

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

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

AIP ADVANCES Vol. 12 ( 4 ) 2022.4

Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：AIP Advances

The effect of low growth rate deposition (LGD) of BaSi2 on the film quality and performance of silicon heterojunction solar cells was investigated. The total thickness of the BaSi2 layer decreased with increasing LGD duration (tLGD). Analysis using Raman spectroscopy indicated that an amorphous Si (a-Si) phase existed on the surface of the BaSi2 layer. The a-Si on the surface was converted into BaSi2 by post-annealing owing to the diffusion of Ba and Si atoms. X-ray diffraction analysis revealed that LGD improved the rate of a-axis orientation and crystallinity. Post-annealing was also observed to have significantly improved these structural properties. Furthermore, the solar cell performance was observed to be strongly dependent on tLGD, and the highest conversion efficiency of 10.62% was achieved by the p-BaSi2/n-c-Si heterojunction solar cells at a tLGD of 6 min. The improved structure and solar cell properties are attributed to improved atom rearrangement during LGD.

DOI： 10.1063/5.0083812

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Fabrication of BaSi<inf>2</inf>homojunction diodes on Nb-doped TiO<inf>2</inf>coated glass substrates by aluminum-induced crystallization and two-step evaporation method Reviewed

Kurokawa Y., Yoshino T., Gotoh K., Miyamoto S., Usami N.

Japanese Journal of Applied Physics Vol. 61 ( SC ) 2022.2

Authorship：Lead author,　Corresponding author Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japanese Journal of Applied Physics

BaSi2 homojunction diodes on Nb-doped TiO2 (TiO2:Nb) coated glass substrates were fabricated using aluminum-induced crystallization (AIC) and a two-step evaporation method. From Raman scattering spectra, the growth of BaSi2 on TiO2:Nb was confirmed when the thickness of poly-Si grown by AIC (AIC-Si) was more than 150 nm. The partial formation of BaSi2 diodes was confirmed from the samples prepared at temperature during AIC TAIC = 475 °C-525 °C. The long-wavelength edge of photoresponsivity of the diodes was located around 950 nm, which corresponds to the bandgap of BaSi2 of 1.3 eV, suggesting that this photocurrent is derived from BaSi2 thin films. At TAIC = 500 °C, the maximum value of photoresponsivity was obtained. Since the largest grains in AIC-Si were also obtained at TAIC = 500 °C, these results suggest that larger grain of AIC-Si leads to the improvement of the quality of BaSi2 thin films themselves and the performance of BaSi2 diodes.

DOI： 10.35848/1347-4065/ac4077

Scopus

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

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

ACS Applied Nano Materials 2022.1

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：ACS Applied Nano Materials

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 Transport 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/cm2) compared with simple a-SiOx:H layer structures. Furthermore, the contact resistivity for the NATURE contact was 13.1 mΩ·cm2, 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 Reviewed

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

Applied Surface Science Vol. 567 2021.11

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Applied Surface Science

We studied the impact of oxidizing pre-treatments (OPT) and post deposition annealing (PDA) on the passivation performance and the hydrogen distribution near the interface between crystalline silicon (c-Si) and hydrogenated amorphous silicon (a-Si:H), the critical functional region in Si heterojunction solar cells. The OPT prior to deposition of the a-Si:H layer consists of immersing the c-Si substrates into hydrogen peroxide solutions, which forms a silicon oxide interlayer. Spectroscopic ellipsometry (SE) indicates that slightly thicker a-Si:H layers result from OPT. The refractive index and the extinction coefficient are increased by inserting the oxide interlayers, suggesting that less deficient and denser a-Si:H layers can be formed. Under optimum conditions, OPT leads to at least 2-fold improvement of the effective photo-generated carrier lifetime. PDA at 200 °C further improves the passivation performance of samples with an interlayer. Hydrogen profiling with nuclear reaction analysis clarifies that higher hydrogen concentrations are present around the heterointerfaces of samples with an interlayer and that these hydrogen concentrations are maintained after PDA. Our results suggest that the oxide interlayer can suppress hydrogen desorption in the initial growth stage of high-quality a-Si:H layers and during subsequent PDA, resulting in excellent passivation performance.

DOI： 10.1016/j.apsusc.2021.150799

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Fabrication of heterojunction crystalline Si solar cells with BaSi2 thin films prepared by a two-step evaporation method Reviewed

Nakagawa Yoshihiko, Takahashi Kazuma, Fujiwara Michinobu, Hara Kosuke O., Gotoh Kazuhiro, Kurokawa Yasuyoshi, Itoh Takashi, Suemasu Takashi, Usami Noritaka

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 60 ( 10 ) 2021.9

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

We have fabricated p-type BaSi2 (p-BaSi2)/n-type crystalline Si (n-c-Si) heterojunction solar cells using thermal evaporation. To control the defect around the heterointerface, samples were fabricated by two methods using different current profiles during evaporation. The one-step method was designed to avoid supplying Ba-rich vapor, and the two-step method was designed to intentionally introduce Ba-rich vapor at the first step. Deep-level transient spectroscopy measurements revealed that defect densities in the n-c-Si side were almost the same for both samples. Open-circuit voltage (V oc) was successfully improved from 319 to 463 mV by the two-step method. This may be due to the increase of carrier density in p-BaSi2 prepared using a two-step method. As a result of optimization, the conversion efficiency of 6.23% was achieved by the heterojunction solar cells.

DOI： 10.35848/1347-4065/ac23ec

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

Miyagawa S., Gotoh K., Kutsukake K., Kurokawa Y., Usami N.

Solar Energy Materials and Solar Cells Vol. 230 2021.9

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Solar Energy Materials and Solar Cells

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 BaSi2 homojunction diodes on glass substrates by aluminum induced crystallization and two-step evaporation method Reviewed International journal

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

Ext. Abstr. 2021 International Conference on Solid State Devices and Materals page： 341 - 342 2021.9

Study on the Morphology of Silicon Nanowire Arrays by Using Highly Doped Silicon Reviewed International journal

Haibin Li, Shinya Kato, Yasuyoshi Kurokawa, Tetsuo Soga

Ext. Abstr. 2021 International Conference on Solid State Devices and Materals page： 311 - 312 2021.9

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

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

Physica Status Solidi (A) Applications and Materials Science 2021.7

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Physica Status Solidi (A) Applications and Materials Science

The impact of the implementation of magnesium interlayer and the layer thickness (tTiOx) of titanium oxide on the electrical properties of TiOx/SiOy/Si heterojunctions is investigated to improve electron transport for use in silicon heterojunction solar cells. The passivation performance is improved with increasing tTiOx. For the samples with Mg interlayer, ohmic contact can be attained for the thicker TiOx layer compared with the sample without Mg interlayer. Schottky contact is mitigated by the TiOx/SiOy stacking layers and Mg interlayer, attributed to the reduction of interfacial energy level by TiOx/SiOy stacking layers and enhanced downward band bending by Mg interlayer. The open-circuit voltage and fill factor of the solar cells are improved by inserting the TiOx/SiOy stack and the Mg interlayer, indicating that the electron selectivity is enhanced. Excellent surface passivation and transport properties can be achieved by controlling TiOx layer thickness and using the Mg interlayer.

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 Reviewed

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

Energies Vol. 14 ( 15 ) 2021.7

Authorship：Last author,　Corresponding author Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Energies

Silicon nanowire (SiNW) metal-oxide-semiconductor (MOS) capacitors with Al2O3/TiO2/Al2O3 (ATA) stacked dielectric films were fabricated by metal-assisted chemical etching (MACE) and atomic layer deposition (ALD). High-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) images revealed that SiNWs were conformally coated with ATA although the cross-sectional shapes of MACE-SiNWs were non-uniform and sharp spikes can be seen locally. The dielectric capacitance density of 5.9 μF/cm2 at V = −4 V of the perfect accumula-tion region was achieved due to the combination of the large surface area of the SiNW array and the high dielectric constant of ATA. The capacitance changed exponentially with the voltage at V < −4.3 V and the capacitance of 84 μF/cm2 was successfully achieved at V = −10 V. It was revealed that not only 3D structure and high-k material but also local nanostructure of SiNWs and stacked dielectric layers could contribute to the considerable high capacitance.

DOI： 10.3390/en14154538

Scopus

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

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

Conference Record of the IEEE Photovoltaic Specialists Conference page： 908 - 911 2021.6

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Conference Record of the IEEE Photovoltaic Specialists Conference

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

Scopus

Versatile fabrication of a passivation material, solute PEDOT:PSS, for a c-Si substrate using alcoholic solvents Reviewed International coauthorship International journal

Sustainable Energy and Fuels Vol. 5 ( 3 ) page： 666 - 670 2021.2

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

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 60 ( SB ) page： SBBF04 2021.1

The impact of highly excessive PbI2 on the correlation of MAPbI(3) perovskite morphology and carrier lifetimes Reviewed International coauthorship International journal

JOURNAL OF MATERIALS CHEMISTRY C Vol. 8 ( 41 ) page： 14481 - 14489 2020.11

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

CURRENT APPLIED PHYSICS Vol. 21 page： 36 - 42 2020.10

Effect of Hydrogen Plasma Treatment on Silicon Quantum Dot Multilayers Using Amorphous SiOx Reviewed International journal

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

Proc. 37th European Photovoltaic Solar Energy Conference and Exhibition page： 83 - 86 2020.9

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 Reviewed International coauthorship International journal

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

MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING Vol. 114 page： 105065 2020.8

Fabrication of silicon-nanocrystals-embedded silicon oxide passivating contacts Reviewed International journal

Proc. 47th IEEE Photovoltaic Specialists Conference Vol. 2020-June page： 0969 - 0972 2020.6

Work function of indium oxide thin films on p-type hydrogenated amorphous silicon Reviewed International journal

Proc. 47th IEEE Photovoltaic Specialists Conference Vol. 2020-June page： 0124 - 0127 2020.6

Impact of deposition of indium tin oxide double layers on hydrogenated amorphous silicon/crystalline silicon heterojunction Reviewed International journal

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

AIP ADVANCES Vol. 10 ( 6 ) page： 065008 2020.6

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

Kimura Yuki, Gotoh Kazuhiro, Kurokawa Yasuyoshi, Usami Noritaka

APPLIED PHYSICS EXPRESS Vol. 13 ( 5 ) page： 051002 2020.5

Synthesis of Mg2Si thin film by thermal treatment under inert gas atmosphere and evaluation of film quality Reviewed International journal

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

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 59 ( SF ) page： SFFB03 2020.4

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

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

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 59 ( SF ) page： SFFA05 2020.4

Influence of the time-dependent vapor composition on structural properties of the BaSi2 thin films fabricated by vacuum evaporation Reviewed International journal

Yoshino Takamasa, Nakagawa Yoshihiko, Kimura Yuki, Fujiwara Michinobu, Kurokawa Yasuyoshi, Usami Noritaka

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 59 ( SF ) page： SFFA10 2020.4

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

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

Journal of Vacuum Science & Technology A Vol. 38 ( 2 ) page： 022410 2020.3

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

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

Journal of Vacuum Science & Technology A Vol. 38 ( 2 ) page： 022415 2020.3

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

Gotoh Kazuhiro, Mochizuki Takeya, Kurokawa Yasuyoshi, Usami Noritaka

PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE Vol. 216 ( 22 ) page： 1900495 2019.11

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

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

AIP Advances Vol. 9 ( 7 ) page： 075115 2019.7

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

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

SUSTAINABLE ENERGY & FUELS Vol. 3 ( 6 ) page： 1448 - 1454 2019.6

Electrical properties of TiO TiO<inf>x</inf>bilayer prepared by atomic layer deposition at different temperatures Reviewed International journal

Proc. 46th IEEE Photovoltaic Specialists Conference Vol. 2 page： 3574 - 3576 2019.6

Impact of size distributions of Ge islands as etching masks for anisotropic etching on formation of anti-reflection structures Reviewed International coauthorship International journal

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

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 58 ( 4 ) page： 045505 2019.4

Epitaxial growth of SiGe on Si substrate by printing and firing of Al–Ge mixed paste Reviewed International journal

S. Fukami, Y. Nakagawa, M. F. Hainey, Jr., K. Gotoh, Y. Kurokawa, M. Nakahara, M. Dhamrin, and N. Usami

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 59 ( SG ) page： SGGF09 2019.3

Silicon Nanowire Heterojunction Solar Cells with an Al2O3 Passivation Film Fabricated by Atomic Layer Deposition Reviewed International journal

Kato Shinya, Kurokawa Yasuyoshi, Gotoh Kazuhiro, Soga Tetsuo

NANOSCALE RESEARCH LETTERS Vol. 14 ( 1 ) page： 99 2019.3

Fabrication of a Silicon Nanowire Solar Cell on a Silicon-on-Insulator Substrate Reviewed International journal

Kato Shinya, Kurokawa Yasuyoshi, Gotoh Kazuhiro, Soga Tetsuo

APPLIED SCIENCES-BASEL Vol. 9 ( 5 ) page： 818 2019.3

Evaluation of Si Nanowire MOS Capacitor Using High-k Dielectric Materials Reviewed International journal

R. Nezasa, Y. Kurokawa, N Usami

Proc. 2018 IEEE 18th International Conference on Nanotechnology (IEEE-NANO) page： 1 - 4 2019.1

Improvement of the Electrical Property of Silicon Nanoparticle Films Reviewed International journal

Shinya Kato, Shinsuke Kumagai, Caixeta Bonfim Gabriel, Eiji Ichihara, Naoki Kishi, Tetsuo Soga

2018 IEEE 7th WCPEC Proceeding page： 0333 - 0337 2018.11

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

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

2018 IEEE 7th WCPEC Proceeding page： 2852 - 2856 2018.11

Local Structure of High Performance TiOxPassivating Layer Revealed by Electron Energy Loss Spectroscopy Reviewed International journal

T. Mochizuki, K. Gotoh, A. Ohta, Y. Kurokawa, S. Miyazaki, T. Yamamoto, N. Usami

2018 IEEE 7th WCPEC Proceeding page： 3896 - 3899 2018.11

Improving intrinsic silicon nanoparticle film by press treatment for use in p-i-n solar cells Reviewed International journal

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

2018 IEEE 7th WCPEC Proceeding page： 317 - 320 2018.11

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

Atsushi Hombe, Yasuyoshi Kurokawa, Kazuhiro Gotoh, Noritaka Usami

2018 IEEE 7th WCPEC Proceeding page： 3097 - 3101 2018.11

Structural, Optical and Electrical Characterization of Heterojunction Rib-Si Solar Cells Reviewed International journal

Makoto Konagai, Rei Kondo, Toshiki Otani, Satomi Takahashi, Kentarou Sawano, Yukimi Ichikawa, Kazuyoshi Nakada, Yasuyoshi Kurokawa

2018 IEEE 7th WCPEC Proceeding Vol. - ( - ) page： - - - 2018.11

Fabrication and properties characterization of BaSi2 thin-films thermally-evaporated on Ge (100) modified substrates Reviewed International journal

Mai Thi Kieu Lien, Nakagawa Yoshihiko, Kurokawa Yasuyoshi, Usami Noritaka

THIN SOLID FILMS Vol. 663 page： 14 - 20 2018.10

Activation mechanism of TiOx passivating layer on crystalline Si Reviewed International journal

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

APPLIED PHYSICS EXPRESS Vol. 11 ( 10 ) page： 102301 2018.10

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

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

Proceedings of the 35th European Photovoltaic Solar Energy Conference and Exhibition page： 636 - 638 2018.9

Investigation of effective near-infrared light-trapping structure with submicron diameter for crystalline silicon thin film solar cells Reviewed International journal

Sei Miki, Kurokawa Yasuyoshi, Kato Shinya, Usami Noritaka

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 57 ( 8 ) page： 08RB21 2018.8

Influence of barrier layer's height on the performance of Si quantum dot solar cells Reviewed International journal

Kitazawa Kouhei, Akaishi Ryushiro, Ono Satoshi, Takahashi Isao, Usami Noritaka, Kurokawa Yasuyoshi

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 57 ( 8 ) page： 08RF08 2018.8

Formation of light-trapping structure using Ge islands grown by gas-source molecular beam epitaxy as etching masks Reviewed International coauthorship International journal

Ota Yushi, Hombe Atsushi, Nezasa Ryota, Yurasov Dmitry, Novikov Alexey, Shaleev Mikhail, Baidakova Natalie, Morozova Elena, Kurokawa Yasuyoshi, Usami Noritaka

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 57 ( 8 ) page： 08RB04 2018.8

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

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

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 57 ( 8 ) page： 08RF09 2018.8

Solid State Devices and Materials FOREWORD Reviewed

Kageshima Hiroyuki, Hosoi Takuji, Iwamoto Satoshi, Arie Takayuki, Fujino Masahisa, Fukuzaki Yuzo, Harada Syunta, Ikegami Masashi, Iwamuro Noriyuki, Johguchi Koh, Kakushima Kuniyuki, Kanaya Haruichi, Kikuchi Akihiko, Kinoshita Kentaro, Kuroda Rihito, Kurokawa Yasuyoshi, Maehashi Kenzo, Maekawa Keiichi, Makino Toshiharu, Matsushima Toshinori, Miyata Toshitaka, Morioka Hiroshi, Morioka Hiroshi, Murugesan Mariappan, Nagashio Kosuke, Nagata Takahiro, Nakatsuka Osamu, Nishiyama Nobuhiko, Oiwa Akira, Okada Hiroyuki, Ono Teruo, Sakamoto Toshitsugu, Sakata Toshiya, Shirao Mizuki, Sukegawa Kazuo, Suzuki Toshikazu, Suzuki Hidetoshi, Taima Tetsuya, Tanaka Tetsu, Tatsuoka Kohichi, Tawara Takehiko, Tsuda Kunio, Yamamoto Kazuhiko

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 57 ( 4 ) 2018.4

Formation of black silicon using SiGe self-assembled islands as a mask for selective anisotropic etching of silicon International coauthorship International journal

Yurasov D. V., Novikov A. V., Shaleev M. V., Baidakova N. A., Morozova E. E., Skorokhodov E. V., Ota Y., Hombe A., Kurokawa Y., Usami N.

MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING Vol. 75 page： 143 - 148 2018.3

Fabrication of silicon nanowire based solar cells using TiO2/Al2O3 stack thin films Reviewed International journal

Yasuyoshi Kurokawa, Ryota Nezasa, Shinya Kato, Hisashi Miyazaki, Isao Takahashi, Noritaka Usami

MRS Advances Vol. 3 ( 25 ) page： 1419 - 1426 2018

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Materials Research Society

To improve conversion efficiency of silicon nanowire (SiNW) solar cells, it is very important to reduce the surface recombination rate on the surface of SiNWs, since SiNWs have a large surface area. We tried to cover SiNWs with aluminum oxide (Al2O3) and titanium oxide (TiO2) by atomic layer deposition (ALD), since Al2O3 grown by ALD provides an excellent level of surface passivation on silicon wafers and TiO2 has a higher refractive index than Al2O3, leading to the reduction of surface reflectance. The effective minority carrier lifetime in SiNW arrays embedded in a TiO2/Al2O3 stack layer of 94 μsec was obtained, which was comparable to an Al2O3 single layer. The surface reflectance of SiNW solar cells was drastically decreased below around 5% in all of the wavelength range using the Al2O3/TiO2/Al2O3 stack layer. Heterojunction SiNW solar cells with the structure of ITO/p-type hydrogenated amorphous silicon (a-Si:H)/n-type SiNWs embedded in Al2O3 and TiO2 stack layer for passivation/n-type a-Si:H/back electrode was fabricated, and a typical rectifying property and open-circuit voltage of 356 mV were successfully obtained.

DOI： 10.1557/adv.2018.40

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Alternative simple method to realize p-type BaSi2 thin films for Si heterojunction solar cell applications Reviewed International journal

Kazuma Takahashi, Yoshihiko Nakagawa, Kosuke O. Hara, Isao Takahashi, Yasuyoshi Kurokawa, Noritaka Usami

MRS Advances Vol. 3 ( 25 ) page： 1435 - 1442 2018

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

A novel preparation method of B-doped p-type BaSi2 (p-BaSi2) is proposed to realize heterojunction crystalline Si solar cells with p-BaSi2. The method consists of thermal evaporation of BaSi2 on B-doped amorphous Si (a-Si). In this study, the effect of a-Si interlayers and substrate temperature during BaSi2 evaporation on the electrical characteristics and crystalline quality of the evaporated films were investigated. While no cracks were found in the BaSi2 films formed using hydrogenated a-Si deposited by plasma enhanced chemical vapor deposition (PECVD), the films formed with sputtered a-Si have cracks. In addition, BaSi2 films formed with a 600 °C substrate temperature using PECVD a-Si showed p-type characteristics. After a post-deposition anneal at 800 °C for 5 minutes, the film hole density was measured at 1.3×1019 cm-3 and boron was found to be uniformly distributed throughout the film. These results show that the proposed method using PECVD is promising to obtain p-BaSi2 thin films with high hole density for p-BaSi2/n-type crystalline Si heterojunction solar cells.

DOI： 10.1557/adv.2018.191

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EFFECT OF NOVEL SUB-MICRON STRUCTURE FABRICATED ONTO CRYSTALLINE SILICON ON OPTICAL PROPERITES AND MINORITY CARRIER LIFETIME Reviewed International journal

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

Proc. Grand Renewable Energy 2018 Vol. 1 ( 0 ) 2018

Selective Etching of Si, SiGe, Ge and Its Usage for Increasing the Efficiency of Silicon Solar Cells Reviewed International coauthorship International journal

N. A. Baidakova, V. A. Verbus, E. E. Morozova, A. V. Novikov, E. V. Skorohodov, M. V. Shaleev, D.V. Yurasov, A. Hombe, Y. Kurokawa, and N. Usami

Semiconductors Vol. 51 ( 12 ) page： 1542 - 1546 2017.12

Development of Spin-coated Copper Iodide Film on Silicon for Use in Hole-selective Contacts Reviewed International journal

K. Gotoh, M. Cui, I. Takahashi, Y. Kurokawa, and N. Usami

Energy Procedia Vol. 124 page： 598 - 603 2017.9

Fabrication of BaSi2 thin films capped with amorphous Si using a single evaporation source Reviewed International journal

Hara Kosuke O., Cham Thi Trinh, Kurokawa Yasuyoshi, Arimoto Keisuke, Yamanaka Junji, Nakagawa Kiyokazu, Usami Noritaka

THIN SOLID FILMS Vol. 636 page： 546 - 551 2017.8

Peeling process of thin-film solar cells using graphene layers Reviewed International journal

R. Ishikawa, Y. Kurokawa, S. Miyajima, and M. Konagai

Applied Physics Express Vol. 10 page： 082301 2017.7

Effects of surface morphology randomness on optical properties of Si-based photonic nanostructures Reviewed International journal

Yasuyoshi Kurokawa, Osamu Aonuma, Takeshi Tayagaki, Isao Takahashi and Noritaka Usami

Jpn. J. Appl. Phys. Vol. 56 ( 8S2 ) page： 08MA02 2017.7

Postannealing effects on undoped BaSi<inf>2</inf>evaporated films grown on Si substrates Reviewed International coauthorship International journal

Takamichi Suhara, Koichi Murata, Aryan Navabi, Kosuke O. Hara, Yoshihiko Nakagawa, Cham Thi Trinh, Yasuyoshi Kurokawa, Takashi Suemasu, Kang L. Wang, Noritaka Usami

Japanese Journal of Applied Physics Vol. 56 ( 5S1 ) page： 05DB05 2017.5

Growth of BaSi2 film on Ge(100) by vacuum evaporation and its photoresponse properties Reviewed International journal

Cham Thi Trinh, Nakagawa Yoshihiko, Hara Kosuke O., Kurokawa Yasuyoshi, Takabe Ryota, Suemasu Takashi, Usami Noritaka

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 56 ( 5 ) page： 05DB06 2017.5

Investigation of p-type emitter layer materials for heterojunction barium disilicide thin film solar cells Reviewed International journal

K. Takahashi, Y. Nakagawa, K. O. Hara, Y. Kurokawa, and N. Usami

Jpn. J. Appl. Phys. Vol. 56 page： 05DB04 2017.4

Influence of Fabrication Processes and Annealing Treatment on the Minority Carrier Lifetime of Silicon Nanowire Films Reviewed International journal

S. Kato, T. Yamazaki, Y. Kurokawa, S. Miyajima, and M. Konagai

Nanoscale Research Letters Vol. 12 page： 242 2017.3

Post-annealing effects on the surface structure and carrier lifetime of evaporated BaSi2 films Reviewed International journal

K.O.Hara, C.T.Trinh, Y.Kurokawa, K.Arimoto,J.Yamanaka, K.Nakagawa, and N.Usami

Jpn. J. Appl. Phys. Vol. 56 page： 04CS07 2017.3

Optical characterization of double-side-textured silicon wafer based on photonic nanostructures for thin-wafer crystalline silicon solar cells Reviewed International journal

T.Tayagaki, D. Furuta, O. Aonuma, I. Takahashi, Y. Hoshi, Y. Kurokawa, and N.Usami

Jpn. J. Appl. Phys. Vol. 56 page： 04CS01 2017.1

Preferred Orientation of BaSi2 Thin Films Fabricated by Thermal Evaporation Reviewed International journal

K. O. Hara, C. T. Trinh, Y. Nakagawa, Y. Kurokawa, K. Arimoto, J. Yamanaka, K. Nakagawa, and N. Usami

JJAP Conf. Proc. Vol. 5 page： 11202 2017.1

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

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

PROC. 2017 IEEE 44TH PHOTOVOLTAIC SPECIALIST CONFERENCE (PVSC) page： 1765 - 1768 2017

Novel light trapping structure by alkaline etching using a Ge dot mask for crystalline Si solar cells Reviewed International journal

Atsushi Hombe, Yasuyoshi Kurokawa, Noritaka Usami

PROC. 2016 IEEE 16th International Conference on Nanotechnology (IEEE-NANO) page： 357 - 360 2016.11

Control of the electrical properties of BaSi <inf>2</inf> evaporated films for solar cell applications Reviewed International journal

Kosuke O. Hara, Cham Thi Trinh, Keisuke Arimoto, Junji Yamanaka, Kiyokazu Nakagawa, Yasuyoshi Kurokawa, Takashi Suemasu, Noritaka Usami

PROC. 2016 IEEE 43RD PHOTOVOLTAIC SPECIALIST CONFERENCE (PVSC) page： 2786 - 2789 2016.11

Application of new doping techniques to solar cells for low temperature fabrication Reviewed International journal

Isao Takahashi, Yasuhiro Sujihara, Huang Yating, Jefferson A. Wibowo, Sergii Tutashkonko, Yasuyoshi Kurokawa, Noritaka Usami

PROC. 43RD IEEE PHOTOVOLTAIC SPECIALISTS CONFERENCE page： 2522 - 2524 2016.11

Effects of Luminescent Coupling in Perovskite/c-Si Multijunction Solar Cells with Nanostructured Interlayer Reviewed International journal

T. Tayagaki, Y. Kurokawa, N. Usami

Proc. 32nd European Photovoltaic Solar Energy Conference and Exhibition page： 205 - 208 2016.9

Structure and physical properties of stable isotopic amorphous carbon films Reviewed International journal

Y. Suzuki, Y. Kurokawa, T. Suzuki, K. Kanda, M. Niibe, M. Nakano, N. Ohtake, H. Akasaka

Diamond and Related Materials Vol. 63 page： 115 - 119 2015.10

Flexible Cu(In,Ga)Se-2 solar cells fabricated using a polyimide-coated soda-lime glass substrate Reviewed International journal

Sadono Adiyudha, Hino Masashi, Ichikawa Mitsuru, Yamamoto Kenji, Kurokawa Yasuyoshi, Konagai Makoto, Yamada Akira

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 54 ( 8 ) page： 08KC16 2015.8

Control of valence band offset at CdS/Cu(In,Ga)Se-2 interface by inserting wide-bandgap materials for suppression of interfacial recombination in Cu(In,Ga)Se-2 solar cells Reviewed International journal

Nishimura Takahito, Hirai Yoshiaki, Kurokawa Yasuyoshi, Yamada Akira

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 54 ( 8 ) page： 08KC08 2015.8

Microstructural characterization of Cu2ZnSn(S,Se)(4) solar cells fabricated from nanoparticles Reviewed International journal

Zhang Yiwen, Suyama Naoki, Goto Masanori, Kuwana Jun, Sugimoto Kanta, Satake Tetsuo, Kurokawa Yasuyoshi, Yin Ming, Yamada Akira

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 54 ( 8 ) page： 08KC05 2015.8

Graphene transparent electrode for thin-film solar cells Reviewed International journal

Ishikawa Ryousuke, Kurokawa Yasuyoshi, Miyajima Shinsuke, Konagai Makoto

PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 12, NO 6 Vol. 6 page： 777 - 780 2015.6

Improvement of Cu2ZnSn(S,Se)(4) solar cell efficiency by surface treatment Reviewed International journal

Furuta Kento, Sakai Noriyuki, Kato Takuya, Sugimoto Hiroki, Kurokawa Yasuyoshi, Yamada Akira

PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS Vol. 6 page： 704 - 707 2015.6

Fabrication of Cu(In,Ga)Se-2 solar cells with a single graded band profile Reviewed International journal

Nishimura Takahito, Kasashima Shunsuke, Hirai Yoshiaki, Kurokawa Yasuyoshi, Yamada Akira

PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS Vol. 252 ( 6 ) page： 1235 - 1238 2015.6

Theoretical and experimental investigation of the recombination reduction at surface and grain boundaries in Cu(In,Ga)Se2 solar cells by valence band control Reviewed International journal

Takahito Nishimura, Yoshiaki Hirai, Yasuyoshi Kurokawa, Akira Yamada

MRS Proceedings Vol. 1771 page： 125 - 131 2015.4

Electrical characterization of Cu(In, Ga)Se-2 thin films peeled off from Mo-coated soda-lime glass substrate by AC Hall measurement Reviewed International journal

Umehara Takeshi, Iinuma Shohei, Sadono Adiyudha, Kurokawa Yasuyoshi, Yamada Akira

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 54 ( 1 ) page： 018001 2015.1

Silicon nanowire arrays passivated by Al2O3/TiO2 stack layers Reviewed International journal

Yasuharu Yamada, Yasuyoshi Kurokawa, Shinya Kato, Akira Yamada

PROC. 40TH IEEE PHOTOVOLTAIC SPECIALISTS CONFERENCE page： 2903 - 2907 2014.10

Effect of Tapered Shape on Performance of Silicon Nanowire Solar Cells Reviewed International journal

Kurokawa Yasuyoshi, Kato Shinya, Konagai Makoto

NEXT GENERATION TECHNOLOGIES FOR SOLAR ENERGY CONVERSION V Vol. 9178 page： 91780N 2014.10

Solution of Roll-over-Shaped J-V Characteristics of Ag(In,Ga)Se2 Solar Cells Reviewed International journal

T. Umehara, S. Iinuma, Y. Kurokawa, A. Yamada

Proc. 29th European Photovoltaic Solar Energy Conference and Exhibition page： 1444 - 1447 2014.9

Diameter Reduction of Silicon Nanowires Using Ozone Oxidation Method for the Application to the All-Silicon Tandem Solar Cells Reviewed International journal

Y. Kurokawa, E. Ishida, Y. Yamada, S. Kato, A. Yamada

Proc. 29th European Photovoltaic Solar Energy Conference and Exhibition page： 298 - 302 2014.9

Silicon quantum dot superlattice solar cell structure including silicon nanocrystals in a photogeneration layer Reviewed International journal

Yamada Shigeru, Kurokawa Yasuyoshi, Miyajima Shinsuke, Konagai Makoto

NANOSCALE RESEARCH LETTERS Vol. 9 page： 246 2014.5

Investigation of hydrogen plasma treatment for reducing defects in silicon quantum dot superlattice structure with amorphous silicon carbide matrix Reviewed International journal

Yamada Shigeru, Kurokawa Yasuyoshi, Miyajima Shinsuke, Konagai Makoto

NANOSCALE RESEARCH LETTERS Vol. 9 page： 72 2014.2

Solid-phase crystallization of amorphous silicon nanowire array and optical properties Reviewed International journal

Ishikawa Ryousuke, Kato Shinya, Yamazaki Tatsuya, Kurokawa Yasuyoshi, Miyajima Shinsuke, Konagai Makoto

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 53 ( 2 ) page： 02BE09 2014.2

Numerical study of Cu(In,Ga)Se-2 solar cell performance toward 23% conversion efficiency Reviewed International journal

Hirai Yoshiaki, Kurokawa Yasuyoshi, Yamada Akira

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 53 ( 1 ) page： 012301 2014.1

Radical-assisted chemical doping for chemically derived graphene Reviewed International journal

Ishikawa Ryousuke, Ko Pil Ju, Bando Masashi, Kurokawa Yasuyoshi, Sandhu Adarsh, Konagai Makoto

NANOSCALE RESEARCH LETTERS Vol. 8 page： 534 2013.12

Improvement of carrier diffusion length in silicon nanowire arrays using atomic layer deposition Reviewed International journal

Kato Shinya, Kurokawa Yasuyoshi, Miyajima Shinsuke, Watanabe Yuya, Yamada Akira, Ohta Yoshimi, Niwa Yusuke, Hirota Masaki

NANOSCALE RESEARCH LETTERS Vol. 8 page： 361 2013.8

Observation of Light Scattering Properties of Silicon Nanowire Arrays Reviewed International journal

Y. Kurokawa, Y. Watanabe, S. Kato, Y. Yamada, A. Yamada, Y. Ohta, Y. Niwa, M. Hirota

Proc. IEEE 39TH PHOTOVOLTAIC SPECIALISTS CONFERENCE (PVSC) page： 1880 - 1884 2013.6

Optical assessment of silicon nanowire arrays fabricated by metal-assisted chemical etching Reviewed International journal

Kato Shinya, Kurokawa Yasuyoshi, Watanabe Yuya, Yamada Yasuharu, Yamada Akira, Ohta Yoshimi, Niwa Yusuke, Hirota Masaki

NANOSCALE RESEARCH LETTERS Vol. 8 page： 216 2013.5

Deposition of Ag(In,Ga)Se-2 Solar Cells by a Modified Three-Stage Method Using a Low-Temperature- Deposited Ag-Se Cap Layer Reviewed International journal

Zhang Xianfeng, Kobayashi Tsuyoshi, Kurokawa Yasuyoshi, Miyajima Shinsuke, Yamada Akira

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 52 ( 5 ) page： 055801 2013.5

Improvement of Electrical Properties of Silicon Quantum Dot Superlattice Solar Cells with Diffusion Barrier Layers Reviewed International journal

Yamada Shigeru, Kurokawa Yasuyoshi, Miyajima Shinsuke, Konagai Makoto

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 52 ( 4 ) page： 04CR02 2013.4

Laser Scribing of W-textured ZnO Substrates Using Green Laser Reviewed International journal

Ryousuke Ishikawa, Hidetoshi Wada, Yasuyoshi Kurokawa, Porponth Sichanugrist, Makoto Konagai

MRS Proceedings Vol. 1493 page： 207 - 212 2013.2

Influence of Surface Recombination on the Performance of SiNW Solar Cells and the Preparation of a Passivation Film Reviewed International journal

Shinya Kato, Yuya Watanabe, Yasuyoshi Kurokawa, Akira Yamada, Yoshimi Ohta, Yusuke Niwa, Masaki Hirota

MRS Proceedings Vol. 1512 page： Mrsf12-1512-ff17-05 2013.2

Numerical Simulation about Effects of Bandgap Grading in Cu(In,Ga)Se-2 with a Bandgap of 1.4 eV on Solar Cell Performance Reviewed International journal

Hirai Yoshiaki, Suzuki Ryotaro, Kurokawa Yasuyoshi, Yamada Akira

PROC. IEEE 39TH PHOTOVOLTAIC SPECIALISTS CONFERENCE (PVSC) page： 3307 - 3309 2013

Numerical Approach to the Investigation of Performance of Silicon Nanowire Solar Cells Embedded in a SiO2 Matrix Reviewed International journal

Kurokawa Yasuyoshi, Kato Shinya, Watanabe Yuya, Yamada Akira, Konagai Makoto, Ohta Yoshimi, Niwa Yusuke, Hirota Masaki

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 51 ( 11 ) page： 11PE12 2012.11

Layer-by-Layer Assembled Transparent Conductive Graphene Films for Silicon Thin-Film Solar Cells Reviewed International journal

Ishikawa Ryousuke, Bando Masashi, Wada Hidetoshi, Kurokawa Yasuyoshi, Sandhu Adarsh, Konagai Makoto

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 51 ( 11 ) page： 11PF01 2012.11

Growth of Ag(In,Ga)Se-2 Films by Modified Three-Stage Method and Influence of Annealing on Performance of Solar Cells Reviewed International journal

Zhang Xianfeng, Kobayashi Tsuyoshi, Kurokawa Yasuyoshi, Yamada Akira

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 51 ( 10 ) page： 10NC05 2012.10

Numerical Approach to the Performance of Silicon Quantum Dots Superlattice Solar Cells Taking into Account the Quantum Effect Reviewed International journal

Kurokawa Yasuyoshi, Yamada Shigeru, Konagai Makoto

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 51 ( 10 ) page： 10NE09 2012.10

Improvement of the Band Profile of Cu(In,Ga)Se-2 Solar Cells with High-Ga Content Prepared Using a Five-Stage Method Reviewed International journal

Hirai Yoshiaki, Hidaka Yukiya, Kurokawa Yasuyoshi, Yamada Akira

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 51 ( 10 ) page： 10NC03 2012.10

High Temperature Preparation of Cu(In,Ga)Se2 Thin Films with High Ga Content Reviewed International journal

Y. Hirai, T. Kashima, Y. Kurokawa, A. Yamada

Proc. 27th European Photovoltaic Solar Energy Conference and Exhibition page： 2321 - 2323 2012.9

Layer-by-layer assembled transparent conductive graphene films for solar cells application Reviewed International journal

Ryousuke Ishikawa, Masashi Bando, Yasuyoshi Kurokawa, Adarsh Sandhu, Makoto Konagai

MRS Proceedings Vol. 1451 page： 75 - 81 2012.7

Effect of the Quantum Size Effect on the Performance of Solar Cells with a Silicon Nanowire Array Embedded in SiO2 Reviewed International journal

Yasuyoshi Kurokawa, Shinsuke Miyajima, Akira Yamada, Makoto Konagai

MRS Proceedings Vol. 1439 page： 145 - 150 2012.6

Estimation of the Crystallinity of P-type Hydrogenated Nanocrystalline Cubic Silicon Carbide by Conductive Atomic Force Microscopy Reviewed International journal

Daisuke Hamashita, Yasuyoshi Kurokawa, Makoto Konagai

MRS Proceedings Vol. 1426 page： 347 - 352 2012.5

Characterization of Ag(In, Ga)Se2/CdS interface in AIGS solar cell by HAADF-STEM measurement Reviewed International journal

Zhang Xianfeng, Kobayashi Tsuyoshi, Kurokawa Yasuyoshi, Miyajima Shinsuke, Yamada Akira

PROC. 37TH IEEE PHOTOVOLTAIC SPECIALISTS CONFERENCE page： 149 - 152 2012.4

High thermostable and conductive niobium doped titanium oxide for the application to a diffusion barrier layer of silicon quantum dot superlattice solar cell structure Reviewed International journal

Shigeru Yamada, Yasuyoshi Kurokawa, Makoto Konagai

PROC. 37TH IEEE PHOTOVOLTAIC SPECIALISTS CONFERENCE page： 2113 - 2116 2012.4

Metal-Assisted Chemical Etching Using Silica Nanoparticle for the Fabrication of a Silicon Nanowire Array Reviewed International journal

Kato Shinya, Watanabe Yuya, Kurokawa Yasuyoshi, Yamada Akira, Ohta Yoshimi, Niwa Yusuke, Hirota Masaki

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 51 ( 2 ) page： 02BP09 2012.2

Experimental and Theoretical Evaluation of Cu(In,Ga)Se-2 Concentrator Solar Cells Reviewed International journal

Hirai Yoshiaki, Nagashima Hiroshi, Kurokawa Yasuyoshi, Yamada Akira

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 51 ( 1 ) page： 014101 2012.1

Comparison of Interface Characterization between Ag(In,Ga)Se-2 and Cu(In,Ga)Se-2 Solar Cells by High-Angle-Annular Dark-Field Scanning Transmission Electron Microscopy Reviewed International journal

Zhang Xianfeng, Kobayashi Tsuyoshi, Kurokawa Yasuyoshi, Tashiro Yoshiyuki, Ohtsuka Masahiro, Yamada Tomoyuki, Yamada Akira

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 50 ( 12 ) page： 126603 2011.12

第三世代太陽電池研究開発の現状--シリコン量子ドットを用いた次世代太陽電池 (特集次世代太陽電池開発の最前線) Reviewed

黒川康良, 小長井誠

ケミカルエンジニヤリング Vol. 56 ( 3 ) page： 232 - 237 2011.3

Size-Controlled Silicon Quantum Dots Superlattice for Thin-Film Solar Cell Applications Reviewed International journal

Yasuyoshi Kurokawa, Shinsuke Miyajima, Akira Yamada, Makoto Konagai

MRS Proceedings Vol. 1101 page： 1101-KK12-01 2011.2

Preparation of p-type Hydrogenated Nanocrystalline Cubic Silicon Carbide/n-type Crystalline Silicon Heterojunction Solar Cells by VHF-PECVD Reviewed International journal

Hamashita Daisuke, Kurokawa Yasuyoshi, Konagai Makoto

Energy Procedia Vol. 10 page： 14 - 19 2011

Light management of a-Si:H solar cells using textured zinc oxide with adjustable haze values Reviewed International journal

Zhang Liping, Yunaz Ihsanul Afdi, Kasashima Shunsuke, Wada Hidetoshi, Hongsingthong Aswin, Krajangsang Taweewat, Kurokawa Yasuyoshi, Konagai Makoto

PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS Vol. 8 ( 10 ) page： 2998 - 3001 2011

Introduction of Oxygen into the Barrier Layers in a Si Quantum Dots Superlattice Using a-SiC Matrix to Improve the Solar Cell Performance Reviewed International journal

Y. Kurokawa, S. Yamada, S. Miyajima, A. Yamada, M. Konagai

Proc. 25th European Photovoltaic Solar Energy Conference and Exhibition / 5th World Conference on Photovoltaic Energy Conversion page： 2748 - 2752 2010.9

Development of SiOx and SiOx/ SiO2 Superlattice for Application in Solar Cells Reviewed International coauthorship International journal

S. Ray, S. Mukhopadhyay, Y. Kurokawa, M. Konagai

Proc. 25th European Photovoltaic Solar Energy Conference and Exhibition / 5th World Conference on Photovoltaic Energy Conversion page： 591 - 594 2010.9

Effects of oxygen addition on electrical properties of silicon quantum dots/amorphous silicon carbide superlattice Reviewed International journal

Kurokawa Yasuyoshi, Yamada Shigeru, Miyajima Shinsuke, Yamada Akira, Konagai Makoto

CURRENT APPLIED PHYSICS Vol. 10 ( 3 ) page： S435 - S438 2010.5

HIGH OPEN-CIRCUIT VOLTAGE OXYGEN-CONTAINING SILICON QUANTUM DOTS SUPERLATTICE SOLAR CELLS Reviewed International journal

Yamada Shigeru, Kurokawa Yasuyoshi, Miyajima Shinsuke, Yamada Akira, Konagai Makoto

PROC. 35TH IEEE PHOTOVOLTAIC SPECIALISTS CONFERENCE page： 766 - 769 2010

Effects of Nitrogen on the Electrical Properties of Si Quantum Dots Superlattice Using a-SiC Matrix Reviewed International journal

Y. Kurokawa, S. Tomita, S. Miyajima, A. Yamada, M. Konagai

Proc. 24th European Photovoltaic Solar Energy Conference page： 398 - 403 2009.9

High-Efficiency Novel Solar Cells : Present Status of Third Generation Photovoltaics(<Special Issue>Future Prospects of Solar Cell Development) Reviewed

KONAGAI Makoto, KUROKAWA Yasuyoshi

Journal of the Japan Institute of Energy Vol. 87 ( 3 ) page： 193 - 198 2008.3

Authorship：Last author Language：Japanese

Present status of third generation photovoltaics is reviewed. Recently, inter-band solar cells, hot carrier solar cells or all silicon tandem solar cells have been proposed to overcome the efficiency limit of conventional solar cells, and this kind of new concepts is named as "the third generation solar cell". All silicon tandem solar cells are the most promising as the third generation solar cell, since silicon is abundant on the earth and nontoxic. To realize all silicon tandem solar cells, silicon quantum dots superlattice (Si-QDSL) is the most important structure since Si-QDSL enables us to obtain bandgap-controlled materials. Si-QDSL is composed of the aligned silicon quantum dots in a silicon-based wide gap material. In this paper, preparation techniques and preliminary optical properties of Si/SiO, Si/SiN and Si/SiC-QDSL's will be presented.

OBSERVATION OF THE PHOTOVOLTAICS EFFECT FROM THE SOLAR CELLS USING SILICON QUANTUM DOTS SUPERLATTICE AS A LIGHT ABSORPTION LAYER Reviewed International journal

Kurokawa Yasuyoshi, Tomita Shigeki, Miyajima Shinsuke, Yamada Akira, Konagai Makoto

PROC. 33RD IEEE PHOTOVOLTAIC SPECIALISTS CONFERENCE page： 858 - 863 2008

TiO2-Coated Transparent Conductive Oxide (SnO2:F) Films Prepared by Atmospheric Pressure Chemical Vapor Deposition with High Durability against Atomic Hydrogen. Reviewed

M. Kambe, K. Sato, D. Kobayashi, Y. Kurokawa, S. Miyajima, M. Fukawa, N. Taneda, A. Yamada, M. Konagai

Japanese Journal of Applied Physics Vol. 45 page： L291 - L293 2006.3

Nanocrystalline silicon in amorphous silicon carbide matrix for Si quantum dots superlattice Reviewed International journal

Kurokawa Yasuyoshi, Miyajima Shinsuke, Yamada Akira, Konagai Makoto

PROC. 2006 IEEE 4th World Conference on Photovoltaic Energy Conversion page： 138 - 141 2006

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