研究者詳細 - 黒川　康良

論文 - 黒川　康良

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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 査読有り

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

DISCOVER NANO 18 巻 ( 1 ) 頁： 72 2023年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：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

Web of Science

Scopus

PubMed

Performance enhancement of droplet-based electricity generator using a CYTOP intermediate layer 査読有り

Japanese Journal of Applied Physics 62 巻 ( SC ) 頁： SC1032 2023年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：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/acaca7

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

Li Haibin, Kato Shinya, Kurokawa Yasuyoshi, Soga Tetsuo

e-Journal of Surface Science and Nanotechnology advpub 巻 ( 0 ) 2022年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：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 査読有り

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

Nano Express 3 巻 ( 4 ) 2022年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：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

Scopus

Performance enhancement of droplet-based electricity generator using a CYTOP intermediate layer 査読有り国際誌

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 頁： 145 - 146 2022年9月

Preparation and thermoelectric characterization of boron-doped silicon nanocrystals/silicon oxide multilayers 査読有り国際誌

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 頁： 147 - 148 2022年9月

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

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

Solar RRL 2022年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：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

Scopus

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

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

Thin Solid Films 764 巻頁： 139597 2022年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：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 査読有り

Shinya Kato, Yasuhoshi Kurakawa, Tetsuo Soga

Results in Optics 9 巻頁： 100296 2022年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：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 査読有り国際誌

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

Proc. 8th World Conference on Photovoltaic Energy Conversion 頁： 230 - 233 2022年9月

Improvement of Passivation Performance of Silicon Nanocrystal/Silicon Oxide Compound Layer by Hydrogen Plasma Treatment 査読有り国際誌

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

Proc. 8th World Conference on Photovoltaic Energy Conversion 頁： 402 - 405 2022年9月

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

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

AIP ADVANCES 12 巻 ( 4 ) 2022年4月

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）出版者・発行元：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

Web of Science

Scopus

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 査読有り

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

Japanese Journal of Applied Physics 61 巻 ( SC ) 2022年2月

担当区分：筆頭著者,　責任著者記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：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 査読有り

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

ACS Applied Nano Materials 2022年1月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：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

Scopus

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

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

Applied Surface Science 567 巻 2021年11月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：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

Scopus

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

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

JAPANESE JOURNAL OF APPLIED PHYSICS 60 巻 ( 10 ) 2021年9月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：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

Web of Science

Scopus

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

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

Solar Energy Materials and Solar Cells 230 巻 2021年9月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：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

Scopus

Fabrication of BaSi2 homojunction diodes on glass substrates by aluminum induced crystallization and two-step evaporation method 査読有り国際誌

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

Ext. Abstr. 2021 International Conference on Solid State Devices and Materals 頁： 341 - 342 2021年9月

Study on the Morphology of Silicon Nanowire Arrays by Using Highly Doped Silicon 査読有り国際誌

Haibin Li, Shinya Kato, Yasuyoshi Kurokawa, Tetsuo Soga

Ext. Abstr. 2021 International Conference on Solid State Devices and Materals 頁： 311 - 312 2021年9月

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

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

Physica Status Solidi (A) Applications and Materials Science 2021年7月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：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

Scopus

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論文 - 黒川　康良