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Journal Articles

Recovery of radiation degradation on inverted metamorphic triple-junction solar cells by light soaking

Shibata, Yuichi*; Imaizumi, Mitsuru*; Sato, Shinichiro; Oshima, Takeshi; Ooka, Sachiyo*; Takamoto, Tatsuya*

Proceedings of 11th International Workshop on Radiation Effects on Semiconductor Devices for Space Applications (RASEDA-11) (Internet), p.65 - 68, 2015/11

Radiation response is one of the important properties for space solar cells. It should be well understood so as to accurately predict their degradation in orbit and also to improve their radiation tolerance. Recently, a phenomenon, recovery from the radiation degradation by light soaking, on inverted metamorphic (IMM) triple-junction (3J) solar cells was found out. In this work, the light soaking annealing effects on electron irradiated IMM 3J solar cells are reported. IMM 3J solar cells irradiated with 1 MeV electrons with the fluence of 3$$times$$10$$^{15}$$ e$$^-$$/cm$$^2$$ showed the recovery of open-circuit voltage, Voc, up to 43 mV after light (AM0, 1 sun) soaking of 3 hours. The increment of the electroluminescence intensity for InGaP in the IMM 3J cells due to the light soaking suggests that the Voc recovery occurs in InGaP top-cell rather than GaAs middle-cell or InGaAs bottom-cell.

Journal Articles

First flight demonstration of glass-type space solar sheet

Shimazaki, Kazunori*; Kobayashi, Yuki*; Takahashi, Masato*; Imaizumi, Mitsuru*; Murashima, Mio*; Takahashi, Yu*; Toyota, Hiroyuki*; Kukita, Akio*; Oshima, Takeshi; Sato, Shinichiro; et al.

Proceedings of 40th IEEE Photovoltaic Specialists Conference (PVSC-40) (CD-ROM), p.2149 - 2154, 2014/06

The electrical performance of a glass-type space solar sheet (G-SSS) was demonstrated in space. G-SSS comprises InGaP/GaAs dual-junction and InGaP/GaAs/InGaAs triplejunction solar cells. It is lightweight solar generation sheet, less than 0.5 mm thick. It is mounted on the "HISAKI" (SPRINT-A) small scientific satellite, which was launched on September 14, 2013. The initial flight data were successfully acquired and this flight demonstration was a world-first experiment for G-SSS using III-V multi-junction thin-film solar cells. The cells demonstrated superior performance and the electrical outputs matched the flight prediction.

Journal Articles

First flight demonstration of film-laminated InGaP/GaAs and CIGS thin-film solar cells by JAXA's small satellite in LEO

Morioka, Chiharu*; Shimazaki, Kazunori*; Kawakita, Shiro*; Imaizumi, Mitsuru*; Yamaguchi, Hiroshi*; Takamoto, Tatsuya*; Sato, Shinichiro; Oshima, Takeshi; Nakamura, Yosuke*; Hirako, Keiichi*; et al.

Progress in Photovoltaics; Research and Applications, 19(7), p.825 - 833, 2011/11

 Times Cited Count:21 Percentile:68.5(Energy & Fuels)

Journal Articles

Theoretical optimization of base doping concentration for radiation resistance of InGaP subcells of InGaP/GaAs/Ge based on minority-carrier lifetime

Elfiky, D.*; Yamaguchi, Masafumi*; Sasaki, Takuo*; Takamoto, Tatsuya*; Morioka, Chiharu*; Imaizumi, Mitsuru*; Oshima, Takeshi; Sato, Shinichiro; Elnawawy, M.*; Eldesoky, T.*; et al.

Japanese Journal of Applied Physics, 49(12), p.121201_1 - 121201_7, 2010/12

 Times Cited Count:11 Percentile:45.91(Physics, Applied)

One of the fundamental objectives for research and development of space solar cells is to improve their radiation resistance. InGaP solar cells with low base carrier concentrations under low-energy proton irradiations have shown high radiation resistances. In this study, an analytical model for low-energy proton radiation damage to InGaP subcells based on a fundamental approach for radiative and nonradiative recombinations has been proposed. The radiation resistance of InGaP subcells as a function of base carrier concentration has been analyzed by using the radiative recombination lifetime and damage coefficient K for the minority-carrier lifetime of InGaP. Numerical analysis shows that an InGaP solar cell with a lower base carrier concentration is more radiation-resistant. Satisfactory agreements between analytical and experimental results have been obtained, and these results show the validity of the analytical procedure. The damage coefficients for minority-carrier diffusion length and carrier removal rate with low-energy proton irradiations have been observed to be dependent on carrier concentration through this study. As physical mechanisms behind the difference observed between the radiation-resistant properties of various base doping concentrations, two mechanisms, namely, the effect of a depletion layer as a carrier collection layer and generation of the impurity-related complex defects due to low-energy protons stopping within the active region, have been proposed.

Journal Articles

Effect of base doping concentration on radiation-resistance for GaAs sub-cells in InGaP/GaAs/Ge

Elfiky, D.*; Yamaguchi, Masafumi*; Sasaki, Takuo*; Takamoto, Tatsuya*; Morioka, Chiharu*; Imaizumi, Mitsuru*; Oshima, Takeshi; Sato, Shinichiro; Elnawawy, M.*; Eldesoky, T.*; et al.

Japanese Journal of Applied Physics, 49(12), p.121202_1 - 121202_5, 2010/12

 Times Cited Count:6 Percentile:31.11(Physics, Applied)

GaAs solar cells with the lower base carrier concentration under low energy proton irradiations had shown experimentally the better radiation-resistance. Analytical model based on fundamental approach for radiative and non-radiative recombination has been proposed for radiation damage in GaAs sub-cells. The radiation resistance of GaAs sub-cells as a function of base carrier concentration has been analyzed by using radiative recombination lifetime and damage coefficient for minority carrier lifetime. Numerical analysis shows good agreement with experimental results. The effect of carrier concentration upon the change of damage constant and carrier removal rate have been studied.

Journal Articles

Study the effects of proton irradiation on GaAs/Ge solar cells

Elfiky, D.*; Yamaguchi, Masafumi*; Sasaki, Takuo*; Takamoto, Tatsuya*; Morioka, Chiharu*; Imaizumi, Mitsuru*; Oshima, Takeshi; Sato, Shinichiro; Elnawawy, M.*; Eldesuky, T.*; et al.

Proceedings of 35th IEEE Photovoltaic Specialists Conference (PVSC-35) (CD-ROM), p.002528 - 002532, 2010/06

 Times Cited Count:5 Percentile:87.77

Proton energy dependence of radiation damage to GaAs/Ge solar cells irradiated with protons with various energies (50 keV, 200 keV, 1 MeV and 9.5 MeV) were analyzed by using PC1D simulation together with SRIM simulations to investigate their electrical properties. The degradation of the open-circuit voltage is highest for 50 keV irradiation and lowest for 9.5 MeV irradiation. According to SRIM simulations the above changes in electrical properties are mainly related to damage in different regions of the solar sells.

Journal Articles

Durability of triple-junction solar cell for HIHT environments, venus and mercury exploration missions

Imaizumi, Mitsuru*; Toyota, Hiroyuki*; Shimada, Takanobu*; Ogawa, Hiroyuki*; Tajima, Michio*; Hisamatsu, Tadashi*; Nakamura, Kazuyo*; Takamoto, Tatsuya*; Sato, Shinichiro; Oshima, Takeshi

Proceedings of the 8th International Workshop on Radiation Effects on Semiconductor Devices for Space Applications (RASEDA-8), p.127 - 130, 2008/12

Results of our study of effects of high-light-intensity and high-temperature conditions (HIHT) on the output performance of an InGaP/GaAs/Ge triple-junction solar cell are described herein. The HIHT conditions are adjusted for spacecraft environments expected for a Venus mission (Planet-C) and a Mercury mission (MMO) to be undertaken by the Japan Aerospace Exploration Agency (JAXA). Measurements of current-voltage characteristics under high light intensity for wide range of cell temperatures exhibit a kinked pattern at 0 current at +200$$^{circ}$$C. The thermal cycle test results for bare cells with a wide temperature range show no output performance degradation. Continuous operation tests of 3J cells under HIHT conditions reveal gradual current output degradation, implying that solar panel design should address decreased output specifically.

Journal Articles

Durability of triple-junction solar cell for HIHT environments, venus and mercury exploration missions

Imaizumi, Mitsuru*; Toyota, Hiroyuki*; Shimada, Toru*; Ogawa, Hiroyuki*; Tajima, Michio*; Hisamatsu, Tadashi*; Nakamura, Kazuyo*; Takamoto, Tatsuya*; Sato, Shinichiro; Oshima, Takeshi

Proceedings of 8th European Space Power Conference (CD-ROM), 6 Pages, 2008/09

Results of our study of effects of high-light-intensity and high-temperature conditions (HIHT) on the output performance of an InGaP/GaAs/Ge triple-junction solar cell are described herein. The HIHT conditions are adjusted for spacecraft environments expected for a Venus mission (Planet-C) and a Mercury mission (MMO) to be undertaken by the Japan Aerospace Exploration Agency (JAXA). Measurements of currentvoltage characteristics under high light intensity for a wide range of cell temperatures exhibit a kinked pattern at 0 current at +200$$^{circ}$$C. The thermal cycle test results for bare cells with a wide temperature range show no output performance degradation. Continuous operation tests of 3J cells under HIHT conditions reveal gradual current output degradation, implying that solar panel design should address decreased output specifically.

Oral presentation

Clinical study of neutron capture therapy for locally recurrent breast cancer

Yanagie, Hironobu*; Sakurai, Yoshinori*; Kumada, Hiroaki; Naka, Hideji*; Furuya, Yoshitaka*; Takamoto, Shinichi*; Ono, Koji*; Takahashi, Hiroyuki*

no journal, , 

no abstracts in English

Oral presentation

Development of high-efficiency thin film solar cells for space use

Imaizumi, Mitsuru*; Kobayashi, Yuki*; Shimazaki, Kazunori*; Takahashi, Masato*; Sato, Shinichiro; Oshima, Takeshi; Takamoto, Tatsuya*

no journal, , 

no abstracts in English

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