  Space solar cells radiation hardness is of fundamental importance in view of
the future missions towards harsh radiation environment (like e.g. missions to
Jupiter) 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
bottom cells. Very surprising was the germanium bottom junction that showed
very high degradation after protons whereas it is quite stable against
electrons. Radiation results have been analyzed by means of the Displacement
Damage Dose method and DLTS spectroscopy.
