High-energy electrons are known to induce Cu-related defects in Cu (In, Ga) Se-2 material. CIGS cells were irradiated with electrons with the energy of 250 keV at temperatures below 150 K to avoid the recovery of generated defects due to a thermal annealing effect. The carrier density increased in line with increasing electron fluence. Copper vacancy (V-Cu) could result in increased carrier density as the shallow acceptor level (V-Cu) is assumed to be the main defect in the CIGS absorbing layer. In the case of 1 MeV electron irradiation, however, a decrease in the carrier density of CIGS solar cells has been reported. The activation energies for the thermal annealing of defects induced by 250 keV electrons differ from those induced by 1 MeV electrons. The Cu-related defects in CIGS induced by 250 keV electron irradiation are not thought to degrade CIGS solar cell output performance. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved.