Influence of Na and H2O on the surface properties of Cu(In,Ga)Se, thin films

The influence of humidity on the electronic structure of Na-containing polycrystalline Cu(In,Ga)Se-2 thin films on soda-lime glass substrates has been investigated by x-ray and UV photoemission as well as by Auger electron spectroscopy. Different interactions between coadsorbed Na, H2O, and the Cu(In,Ga)Se-2 surface are revealed at low temperatures and upon annealing at room temperature. Both, reversible and irreversible interactions such as a H2O-induced reduction of the Na surface content and the formation of a Na-O-Cu(In,Ga)Se-2 complex are observed. Our findings can be correlated with the influence of ambient conditions on Cu(In,Ga)Se-2 solar cell adsorbers and demonstrate the importance of adequate encapsulation of Na-containing Cu(In,Ga)Se-2-based thin-film solar cells. (C) 1997 American Institute of Physics.