NOVELTY - The structure (20) has an n-type semiconductor layer (25) i.e. buffer layer, exhibiting photo catalyst behavior and formed on a p-type semiconductor layer (24) i.e. copper indium gallium selenium (CIGS) layer, where the n-type semiconductor layer is free of cadmium. A transparent conductive layer (26) is formed on the n-type semiconductor layer. A high resistivity layer (23) is formed between a metal layer (22) and a transparent conductive layer, where resistivity of the high resistivity layer is higher than that of the n-type semiconductor layer or the p-type semiconductor layer.    USE - CIGS photovoltaic cell structure.    ADVANTAGE - The structure including the n-type semiconductor layer with photo catalyst characteristic in a place of utilization of cadmium is formed in the cell structure, thus eliminating waste liquid and related cadmium contamination created during manufacturing process. The structure allows cadmium sulfate too be replaced by the n-type semiconductor layer of titanium oxide or tungsten oxide in consideration of the photo catalyst characteristic, so that the contamination caused by the utilization of cadmium sulfate can be effectively avoided.    DETAILED DESCRIPTION - The p-type semiconductor layer is made of copper indium gallium selenium sulfur, copper indium gallium selenium, copper indium sulfur, copper indium selenium. The n-type semiconductor layer is made of metal oxide. The metal oxide material is selected from the group consisting of vanadium oxide, tungsten oxide, molybdenum oxide, copper oxide, iron oxide, tin oxide, titanium oxide, zinc oxide, zirconium oxide, lanthanum oxide, niobium oxide, indium tin oxide, strontium oxide, cadmium oxide, indium oxide, or the mixture or alloys. The transparent conductive layer material is selected from the group consisting of indium tin oxide, indium zinc oxide, aluminum zinc oxide, gallium zinc oxide, aluminum gallium zinc oxide, cadmium tin oxide, zinc oxide and zirconium dioxide.    DESCRIPTION OF DRAWING(S) - The drawing shows a cross sectional view of a photovoltaic cell structure.    CIGS photovoltaic cell structure (20)    Metal layer (22)    High resistivity layer (23)    P-type semiconductor layer (24)    N-type semiconductor layer (25)    Transparent conductive layer (26)