Effects of proton irradiation on n+p InGaP solar cells

3 MeV proton irradiation effects on In0.5Ga0.5P single junction and In0.5Ga0.5P/GaAs tandem solar cells have been investigated for the fluence range from 1×1011 to 1×1013 cm−2. The overall radiation degradation of In0.5Ga0.5P/GaAs tandem cells was higher than In0.5Ga0.5P single junction cells. It was observed that the spectral response of the GaAs bottom cell degrades more than the InGaP top cell. Proton irradiation decreases the longer wavelength spectral response more significantly than the shorter wavelength in both In0.5Ga0.5P and In0.5Ga0.5P/GaAs cells. The difference in the degradation properties of n+p and p+n polarity InGaP solar cells is discussed. The radiation response of a tandem n+p InGaP/GaAs cell is very nearly that which is predicted from the information of these two cells independently. The minority-carrier diffusion length in the base layer was determined from the spectral response data. The minority-carrier diffusion length damage coefficient KL was analyzed for In0.5Ga0.5P and GaAs cells. The minority-carrier injection-enhanced annealing of radiation-induced defects in In0.5Ga0.5P and In0.5Ga0.5P/GaAs cells were also observed.