Optical and electrical properties of electron-irradiated Cu(In,Ga)Se2 solar cells

The optical and electrical properties of electron-irradiated Cu(In,Ga)Se-2 (CIGS) solar cells and the thin films that composed the CIGS solar cell structure were investigated. The transmittance of indium tin oxide (ITO), ZnO:Al, ZnO:Ga, undoped ZnO, and CdS thin films did not change for a fluence of up to 1.5 x 10(18) cm(-2). However, the resistivity of ZnO:Al and ZnO:Ga, which are generally used as window layers for CIGS solar cells, increased with increasing irradiation fluence. For CIGS thin films, the photoluminescence peak intensity due to Cu-related point defects, which do not significantly affect solar cell performance, increased with increasing electron irradiation. In CIGS solar cells, decreasing J(SC) and increasing R-s reflected the influence of irradiated ZnO:Al, and decreasing V-OC and increasing R-sh mainly tended to reflect the pn-interface properties. These results may indicate that the surface ZnO:Al thin film and several heterojunctions tend to degrade easily by electron irradiation as compared with the bulk of semiconductor-composed solar cells. (C) 2010 Elsevier B.V. All rights reserved.