Degradation analyses of GaInP/GaAs/Ge solar cells irradiated by 70 keV and 150 keV protons by current-voltage curves under various intensities of light

Low energy protons damage GaInP/GaAs/Ge solar cells seriously. Traditional degradation researches require many supplementary tests, such as quantum efficiency (QE) or photoluminescence (PL). In this paper, we would establish a method that could analysis degradation of solar cells without any other equipment except a solar simulator. A voltage-current analysis technique under various intensities (X) of light was developed to study the degradation mechanisms of proton-irradiated GaInP/GaAs/Ge solar cells. Sum of ideality factor of every sub-cell Σni could be calculated from the change of open circuit voltage (Voc) with light intensities in multi-junction solar cells. The change of ideality factor shows significant increase of Shockley-Read-Hall (SRH) recombination after 70 keV and 150 keV protons irradiation. Shunt resistance Rsh increases with intensities, which is different from silicon solar cells. The change of Rsh with light intensities was used to describe the current mismatch among the sub-cells in the multijunction solar cell. After irradiation, the current mismatch becomes larger. The relative degradation rate is different under different intensities of light. The max-power degradation tends to be smaller at high intensities.