In-situ measurement of triple junction solar cells under low intensity and low temperature (LILT) for deep space mission

1 MeV electron radiation has been conducted to study the radiation hardness of GaInP/GaAs/Ge triple junction (TJ) solar cells. The characterization has been carried out under the conditions of (1) low light intensity and room temperature (LIRT), (2) low light intensity and low temperature (LILT) and (3) high radiation low intensity and low temperature (HRLILT). In LIRT, Jsc is linear with the light intensity, and Voc is linear with the logarithmic change of the intensity. In LILT, the results show that Jsc gradually decreases with the temperature from 300 K to 15 K. Voc increases linearly with the temperature from 300 K to 100 K. While Voc increases sub-linearly with the decreasing temperature under 100 K. The temperature coefficient of Voc (αVoc) of the TJ solar cells in this work are similar under different light intensities. In HRLILT, the results show that the degradation degree of Jsc caused by radiation is related to the light intensity, and more pronounced degradation occurs at lower light intensity. Moreover, TJ solar cells before and after irradiation are with a conversion efficiency of 42.0% and 34.4%, respectively (@0.01sun, 15 K). Promisingly, neither “flat spot” (FS) effects nor shunts effects are observed in this experiment.