Influence of electrical performance on Cu-related defects generated by 250 keV electron irradiation in Cu (In, Ga) Se2 thin-film solar cells

High-energy electrons are known to induce Cu-related defects in Cu (In, Ga) Se2 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 (VCu) could result in increased carrier density as the shallow acceptor level (VCu) 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.

► Cu-related defects generated by electrons in Cu(In, Ga)Se2 do not degrade performance. ► 250 keV electrons could generate Cu-related defects in CIGS solar cells. ► The electrons could increase the carrier density of CIGS solar cells.