Analysis of flight demonstration results of an InGaP/GaAs dual-junction tandem solar cell

The radiation degradation trend of an InGaP/GaAs dual-junction solar cell was studied to validate solar cell degradation-prediction methodologies. Ground irradiation test results and data from a space demonstration test performed in GTO for 600 days were compared. Equivalent fluences of 1 MeV electrons and 10 MeV protons for I_SC, V_OC and P_max were obtained from the remaining factor at the end of the mission. The equivalent fluence of 10 MeV protons for the three output factors agreed better than that of 1 MeV electrons due to the proton-rich radiation environment in orbit. The degradation trends of the dual-junction cell were compared with that of single-junction sub-cells using displacement damage dose. The degradation of the dual-junction cell can be explained by the sub-cell degradation and operation principle of the dual-junction cell. However, the flight cell was found to exhibit faster degradation than expected from the ground test results.