NOVELTY - The method comprises providing a metallic web substrate (100), depositing a first electrode (200) over the substrate, depositing a p-type semiconductor absorber layer (301) over the first electrode, depositing an n-type semiconductor layer (302) over the p-type semiconductor absorber layer, depositing a second electrode over the n-type semiconductor layer, and independently controlling depositing an alkali diffusion barrier layer (201) and depositing a first transition metal layer (202) and depositing a second transition metal layer to control an amount of sodium.    USE - The method is useful for manufacturing a copper indium selenide (CIS) based solar cell.    ADVANTAGE - The method provides simple manufacture of the solar cell with excellent efficiency by diffusing sodium from the glass substrate into the CIS film and effectively controlling the amount of the sodium provided to the CIS film and the speed of the sodium diffusion from the glass substrate.    DETAILED DESCRIPTION - The method comprises providing a metallic web substrate (100), depositing a first electrode (200) over the substrate, depositing a p-type semiconductor absorber layer (301) over the first electrode, depositing an n-type semiconductor layer (302) over the p-type semiconductor absorber layer, depositing a second electrode over the n-type semiconductor layer, and independently controlling depositing an alkali diffusion barrier layer (201), depositing a first transition metal layer (202) and depositing a second transition metal layer to control an amount of sodium diffused into the p-type semiconductor absorber layer and generate a variable sodium content as a function of thickness in the first transition metal layer. The first electrode comprises the first transition metal layer comprising an alkali element or an alkali compound and a lattice distortion element or a lattice distortion compound. The p-type semiconductor absorber layer includes a copper indium selenide based alloy material, and comprises sodium (0.005-1.5 at.%) diffused from the first transition metal layer. The second transition metal layer comprises oxygen containing molybdenum layer that has a higher porosity than the alkali diffusion barrier layer. The sodium diffuses from the first transition metal layer into the p-type semiconductor absorber layer through the second transition metal layer during the step of depositing the p-type semiconductor absorber layer. The alkali diffusion barrier layer comprises oxygen free molybdenum layer that prevents sodium diffusion from the first transition metal layer into the substrate through the alkali diffusion barrier layer. The steps of depositing the alkali diffusion barrier layer, depositing the first transition metal layer and depositing the second transition metal layer comprise sputtering the alkali diffusion barrier layer, sputtering the first transition metal layer and sputtering the second transition metal layer in the same sputtering apparatus. The step of sputtering the first transition metal layer comprises sputtering the first transition metal layer: from a target comprising sodium molybdate; and from a pair of sputtering targets having a different composition from each other. The step of sputtering the alkali diffusion barrier layer occurs: under a first sputtering environment in a first vacuum chamber of a magnetron sputtering system; at a lower pressure than the step of sputtering the second transition metal layer such that the alkali diffusion barrier layer is in compressive stress; and in an oxygen free atmosphere. The step of sputtering the second transition metal layer occurs: under a second sputtering environment in a second vacuum chamber of the magnetron sputtering system different from the first vacuum chamber; and in an oxygen containing atmosphere. The second sputtering environment differs from the first sputtering environment in an argon pressure, oxygen pressure, or nitrogen pressure. The steps of depositing the first electrode, depositing the p-type semiconductor absorber layer, depositing the n-type semiconductor layer and depositing the second electrode comprise sputtering conductive layers of the first electrode, the p-type absorber layer, the n-type semiconductor layer and the conductive layers of the second electrode over the substrate in corresponding process modules of independently isolated and connected process modules without breaking vacuum while passing the metallic web substrate from an input module to an output module through the independently isolated and connected process modules such that the web substrate continuously extends from the input module to the output module while passing through the independently isolated and connected process modules.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic cross-sectional view of a copper indium diselenide based solar cell.    Substrate (100)    First electrode (200)    Alkali diffusion barrier layer (201)    First transition metal layer (202)    P-type semiconductor absorber layer (301)    N-type semiconductor layer. (302)