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Sato, Shinichiro; Miyamoto, Haruki; Imaizumi, Mitsuru*; Shimazaki, Kazunori*; Morioka, Chiharu*; Kawano, Katsuyasu*; Oshima, Takeshi
Proceedings of 17th International Photovoltaic Science and Engineering Conference (PVSEC-17) (CD-ROM), p.502 - 503, 2007/12
Degradation modeling of InGaP/GaAs/Ge triple junction (3J) solar cells with the use of a one dimensional optical device simulator, PC1D, is performed for cell lifetime prediction. By fitting the quantum efficiencies of 3J solar cells degraded by 30 keV, 150 keV, 3 MeV, or 10 MeV proton irradiation, the short circuit currents (Isc) and open circuit voltages (Voc) are simulated. The damage coefficient of minority carrier diffusion length (
) and carrier removal rate (
) of base carrier concentration of each sub cell are also estimated. The values of Isc and Voc obtained using the calculations show good agreement with experimental values. These results confirm that the degradation modeling method is effective for lifetime prediction of 3J solar cells.
Miyamoto, Haruki; Sato, Shinichiro; Oshima, Takeshi; Morioka, Chiharu*; Imaizumi, Mitsuru*; Kawano, Katsuyasu*
Proceedings of 17th International Photovoltaic Science and Engineering Conference (PVSEC-17) (CD-ROM), p.961 - 962, 2007/12
InGaP and Si solar cells are irradiated with 10 MeV protons at fluences up to 
cm
at room temperature (RT) and low temperature (LT). Results show that the remaining factor Voc irradiated at LT is higher than that at RT, and vice versa for Isc. The temperature coefficient of Voc after irradiation is greater than that before irradiation, although the coefficients of Isc are the same before and after irradiation. This degradation of the output performance of these solar cells can be interpreted in terms of a decrease in minority-carrier diffusion length.
Morioka, Chiharu*; Imaizumi, Mitsuru*; Sugimoto, Hiroki*; Sato, Shinichiro; Oshima, Takeshi; Tajima, Michio*
Proceedings of 17th International Photovoltaic Science and Engineering Conference (PVSEC-17) (CD-ROM), p.504 - 505, 2007/12
Radiation resistance of (Al)InGaP solar cells was examined in this study. The epitaxial structure, such as aluminum contents or carrier concentration (CC) in the base layer, is varied, whereas the base layer thickness is maintained at 1 
m. The cells are irradiated with 3 MeV protons up to the fluence of 
cm. Remaining factors of short-circuit current and open-circuit voltage show no significant difference between Al
In
Ga
P and InGaP cells. The graded CC structure in the base layer is ineffective to improve radiation resistance in the case of (Al)InGaP cells with a thick base layer, which implies that radiation degradation is not primarily attributable to the decrease in minority-carrier diffusion length.
Oshima, Takeshi; Sato, Shinichiro; Miyamoto, Haruki; Imaizumi, Mitsuru*; Hanaya, Hiroaki; Kawano, Katsuyasu*
Proceedings of 17th International Photovoltaic Science and Engineering Conference (PVSEC-17) (CD-ROM), p.955 - 956, 2007/12
In this study, we reconsider electron irradiation methods for the evaluation of radiation response of space solar cells. We show irradiation test methods performed at JAEA, such as a sequential method, in which the electrical performance of solar cells is measured outside of an irradiation facility after irradiation, and a simultaneous method, in which the electrical performance of solar cells can be measured in-situ. The results obtained from the sequential method are compared to these obtained from the simultaneous method. The reasonable distance between samples and the accelerator window to take reliable data on the basis of the energy decay of electrons by atmosphere is also discussed.