Radiation induced defects in Cu(In,Ga)Se/sub 2/ solar cells-comparison of electron and proton irradiation

The authors report on irradiation experiments of ZnO/CdS/Cu(In,Ga)Se/sub 2/ heterojunction solar cells with high doses of 1 MeV electrons, 10 MeV (omni-directional) and 4 MeV (uni-directional) protons. Electron irradiation up to 10/sup 18/ cm/sup -2/ is necessary to cause a power conversion efficiency loss of 20-30%. Electrical analysis of irradiated devices shows that the degradation is essentially due to the introduction of (relatively shallow) acceptor-like defects by a rate of approximately 0.02 cm/sup -1/. The decrease of effective doping density is quantified by a rate of 0.045 cm/sup -1/. The degradation upon irradiation with 10 MeV (4 MeV) omni- (uni-)directional proton starts at fluences of 10/sup 13/ cm/sup -2/ (10/sup 12/ cm/sup -2/). The remaining efficiency factor is 50% after a 4 MeV-proton fluence of 10/sup 14/ cm/sup -2/. Proton irradiation affects the open circuit voltage and the fill factor. All irradiated samples exhibit a continuous recovery at room temperature.