NIEL DOSE and DLTS Analyses on Triple and Single Junction solar cells irradiated with electrons and protons

Space solar cell radiation hardness is of fundamental importance in view of the future missions towards harsh radiation environment (like the Jupiter missions) and for the new spacecraft using Electrical Propulsion. In this paper we report the radiation data for triple junction (TJ) solar cells and related component cells. Triple junction solar cells, InGaP top cells and GaAs middle cells degrade after electron radiation as expected. With proton irradiation, a high spread in the remaining factors was observed, especially for the TJ and Ge bottom cells. Radiation results have been analyzed by means of the Displacement Damage Dose method and DLTS spectroscopy. In particular with DLTS spectroscopy it was possible to analyze the nature of a few defects introduced by irradiation inside the GaAs sub cell observing a strong correlation with the Displacement Damage Dose.