Patent ID: 8313976

Claim:
A method of manufacturing a solar cell, comprising: providing a substrate; depositing a first electrode over the substrate wherein the first electrode comprises a first transition metal layer comprising: (i) an alkali element or an alkali compound, and (ii) a lattice distortion element or a lattice distortion compound; depositing at least one p-type semiconductor absorber layer over the first electrode, wherein the p-type semiconductor absorber layer includes a copper indium selenide (CIS) based alloy material; depositing an n-type semiconductor layer over the p-type semiconductor absorber layer; and depositing a second electrode over the n-type semiconductor layer; wherein: the first transition metal layer comprises molybdenum; the alkali element or alkali compound comprises sodium; the lattice distortion compound or lattice distortion element is selected from the group consisting of oxygen, MoO 2 and MoO 3 ; the p-type semiconductor absorber layer comprises 0.005 to 1.5 atomic percent sodium diffused from the first transition metal layer; the first transition metal layer comprises at least 59 atomic percent molybdenum, 5 to 40 atomic percent oxygen and 0.01 to 1.5 atomic percent sodium; the second transition metal layer comprises an oxygen containing molybdenum layer that has a higher porosity than the alkali diffusion barrier layer; 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; and the alkali diffusion barrier layer comprises a substantially oxygen free molybdenum layer which substantially prevents sodium diffusion from the first transition metal layer into the substrate through the alkali diffusion barrier layer.