Development of irradiation methods and degradation modeling for state-of-the-art space solar cells

Oshima, Takeshi; Sato, Shinichiro; Sumita, Taishi*; Nakamura, Tetsuya*; Imaizumi, Mitsuru*

It is very important to understand the radiation response of solar cells since we need to predict the performance degradation of solar cells on space satellites during the missions. In general, the electrical characteristics of solar cells are evaluated before and after electron/proton irradiation, and accelerator facilities are just involved in irradiation (referred to as Sequential method). Japan Atomic Energy Agency (JAEA) together with Japan Aerospace Exploration Agency (JAXA) has developed an in-situ evaluation technique that the electrical characteristics of solar cells can be measured under AM0 light illumination during proton/electron irradiation experiments (referred to as Simultaneous method). Furthermore, a sample holder with a cryogenic system was installed to the irradiation chamber in order to clarify the radiation response of solar cells under low temperature and low light intensity conditions such as missions for Mars or farther planet explorations. Using this unique method, we revealed the radiation degradation of multi-junction solar cells such as InGaP/GaAs/Ge triple junction (3J) solar cells under low temperature. In this paper, irradiation techniques for the evaluation of space solar cells will be introduced. The degradation mechanism of the 3J solar cells, and the modeling of degradation behavior of 3J solar cells will be also discussed.