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Imaizumi, Mitsuru*; Yuri, Yosuke; Bolton, P.; Sato, Shinichiro; Oshima, Takeshi
Proceedings of 38th IEEE Photovoltaic Specialists Conference (PVSC-38) (CD-ROM), p.002831 - 002834, 2012/00
High-energy proton irradiation tests were performed on InGaP/GaAs/Ge triple-junction (3J) solar cells with a variety of beam conditions. Irradiation area of about 80 mm 
80 mm was achieved by two different techniques, namely, the spot beam scanning and the defocused beam uniformization using multi-pole magnets. Degradation trend of the cells irradiated with the defocused uniform beam under a variety of doze rates exhibited no significant difference compared to the trend irradiated with the scanned beam under a constant dose rate. This result is consistent with our previous fundamental study, and indicates possibility of reduction of irradiation test duration. Irradiation experiment with a multiple energy proton beam is planned, and generation of such proton beam is now under development. Once a proton beam with energy spectrum similar to space environment, a number of irradiation tests with different proton energies and also an energy equivalent fluence calculation using relative damage coefficients or displacement damage dose will be unnecessary.
Sato, Shinichiro; Beernink, K.*; Oshima, Takeshi
Proceedings of 38th IEEE Photovoltaic Specialists Conference (PVSC-38) (CD-ROM), p.002856 - 002861, 2012/00
The electrical performance degradation of a-Si/a-SiGe/a-SiGe triple-junction solar cells due to irradiation of protons with different energies and their performance recovery at room temperature just after irradiation are investigated. It was shown that the degradation behavior depended on incident proton energies. It was also shown that all the parameters (short-circuit current, open-circuit voltage, and fill factors) recovered with time after proton irradiation was stopped. In particular, the short-circuit current intensively recovered. This is due to the carrier diffusion length increase which is based on room temperature annealing of radiation defects.
Nakamura, Tetsuya*; Imaizumi, Mitsuru*; Sato, Shinichiro; Oshima, Takeshi
Proceedings of 38th IEEE Photovoltaic Specialists Conference (PVSC-38) (CD-ROM), p.002846 - 002850, 2012/00
Roensch et al. recently proposed a new method of estimating the current-voltage (IV) characteristics of subcells in a multi-junction (MJ) solar cell by using electroluminescence (EL). The estimated IV characteristics of a proton-irradiated MJ solar cell from the IV curve obtained from each subcell agreed well with the actual dark IV (DIV) and light IV (LIV) characteristics, except for series resistance (
) and shunt resistance (
). This method can also clarify of a MJ cells and Rsh of subcells through circuit simulation program. In this work, we applied this method to InGaP/GaAs dual-junction (2J) solar cells in order to obtain the IV characteristics of the InGaP top subcells and GaAs bottom subcells before and after proton irradiation with various fluences. In addition, we succeeded to predict the degradation curve of maximum power (
) of the 2J solar cell where the current-limiting subcell changes from InGaP to GaAs subcell.
