Faculty Profiles - KUROKAWA Yasuyoshi

Papers - KUROKAWA Yasuyoshi

Division display 41 - 60 of about 161 ／ All the affair displays >>

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

Scopus

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

Scopus

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

Web of Science

Scopus

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

Scopus

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

Scopus

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

　 PREV - NEXT 　

<KUROKAWA Yasuyoshi>

Papers - KUROKAWA Yasuyoshi