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 substrate s has been investigated by x-ray and UV photoemission as well as by Au ger electron spectroscopy. Different interactions between coadsorbed N a, H2O, and the Cu(In,Ga)Se-2 surface are revealed at low temperatures and upon annealing at room temperature. Both, reversible and irrevers ible interactions such as a H2O-induced reduction of the Na surface co ntent 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 condition s 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-f ilm solar cells. (C) 1997 American Institute of Physics.