Analysis for Non-Radiative Recombination Loss and Radiation Degradation of Si Space Solar Cells
Masafumi Yamaguchi1, Kan-Hua Lee1, Kenji Araki1, Nobuaki Kojima1, Yasuki Okuno2, Mitsuru Imaizumi3
1Toyota Tech. Inst., Nagoya, Japan
/2JAEA, Tokai, Japan
/3JAXA, Tsukuba, Japan

The silicon space solar cells have contributed to communications, broadcasting, weather forecasting and scientific developments since the Vangurad-1 launched in 1958. Because space solar cells operate under severe conditions such as vacuum, high fluence high energy electrons and protons irradiations and thermal cycle conditions, development of superior radiation resistant and highly reliable space cell are necessary as well as high efficiency and low cost. Development of Si space solar cell has been terminated in 1990ís. This is because InGaP/GaAs/Ge structure high-efficiency triple-junction space solar cells were developed and introduced in the space market. The triple-junction cells also have better radiation resistance. However, triple-junction solar cells are essentially high-cost. Thus, Si solar cells are currently attracting attention again for their relatively low-cost feature with sufficient performance, and they are expected to resume into the space market especially by short-term mission spacecraft designers. Especially, advanced Si solar cells such as passivated emitter, hetero-junction and back contact solar cells are expected to use as space solar cells. In this paper, efficiency potential of crystalline Si space solar cells is analyzed by considering external radiative efficiency (ERE), voltage and fill factor losses. Crystalline Si space solar cells have efficiency potential of more than 26% at AM0 by realizing ERE of 20% from about 0.2% and normalized resistance of less than 0.05 from around 0.15. Non-radiative recombination and resistance losses in Si space solar cells are also discussed. Radiation degradation of Si space solar cells is also analyzed. Potential of advanced Si solar cells such as passivated emitter, hetero-junction and back contact solar cells for space applications is discussed from point view of radiation degradation.