PHOTOASSISTED KELVIN PROBE FORCE MICROSCOPY FOR CHARACTERIZATION OF SOLAR CELL MATERIALS

Abstract

Solar cells attract a great deal of interests nowadays as important measures against the global warming. Among a lot of materials used for the solar cells, multior micro-crystalline materials have a big advantage in their fabrication costs, and multicrystalline Si solar cells, in particular, account for nearly half of the world’s total production volume. Their conversion efficiency reaches 20.4%, which is slightly lower than that in a single crystal one (25.0% maximum), and the existence of the grain boundaries (GBs) in the multicrystalline materials is considered as one cause of degradation of the solar cell performances. For thin film solar cells, on the other hand, Cu(In,Ga)Se 2 [CIGS] materials are hopeful mainly because of its high absorption coefficient as well as its bandgap tunablity by changing their material composition to fit the solar spectrum. Up to now, a lot of works have done to realize the solar cells with the CIGS materials and the world record of the conversion efficiency in the CIGS solar cell has reached very close to 20%, which is nearly comparable with that in the multicrystalline Si solar cell. However, most CIGS materials used for solar