Method and apparatus for controllable sodium delivery for thin film photovoltaic materials

A solar cell, comprising:

• a plastic or metal a substrate which does not provide an available supply of sodium;
• a first electrode located over the substrate, wherein the first electrode comprises a first transition metal layer containing a transition metal and an alkali element or an alkali compound;
• at least one p-type semiconductor absorber layer located over the first electrode, wherein the p-type semiconductor absorber layer includes a copper indium selenide (CIS) based alloy material;
• an n-type semiconductor layer located over the p-type semiconductor absorber layer;
• and
• a second electrode located over the n-type semiconductor layer;
• wherein the first electrode further comprises:
• (ii) an alkali diffusion barrier layer located between the substrate and the first transition metal layer, wherein the alkali diffusion barrier layer is configured to substantially reduce or prevent alkali diffusion from the first transition metal layer into the substrate;
• and
• (ii) a second transition metal layer located between the first transition metal layer and the p-type semiconductor absorber layer, wherein the second transition metal layer comprises a transition metal and has a higher porosity than the alkali diffusion barrier layer and the second transition metal layer permits alkali diffusion from the first transition metal layer into the p-type semiconductor absorber layer,
• wherein a concentration of the alkali or alkali compound in the first transition metal layer is greater than the concentration of the alkali element or alkali compound in the at least one p-type semiconductor absorber layer.

A solar cell, comprising:

• a metal or plastic substrate which does not provide an available supply of sodium;
• a first electrode located over the substrate, wherein the first electrode comprises a first transition metal layer containing:
• (i) a transition metal, (ii) an alkali element or an alkali compound, and (iii) a lattice distortion element or a lattice distortion compound;
• at least one p-type semiconductor absorber layer located over the first electrode, wherein the p-type semiconductor absorber layer includes a copper indium selenide (CIS) based alloy material;
• an n-type semiconductor layer located over the p-type semiconductor absorber layer;
• a second electrode located over the n-type semiconductor layer;
• an alkali diffusion barrier layer located between the substrate and the first transition metal layer, wherein the alkali diffusion barrier layer substantially reduces or prevents alkali diffusion from the first transition metal layer into the substrate;
• and
• a second transition metal layer located between the first transition metal layer and the p-type semiconductor absorber layer, wherein the second transition metal layer comprises a transition metal and has a higher porosity than the alkali diffusion barrier layer and the second transition metal layer permits alkali diffusion from the first transition metal layer into the p-type semiconductor absorber layer,
• wherein a concentration of the alkali element or alkali compound in the first transition metal layer is greater than the concentration of the alkali element or alkali compound in the at least one p-type semiconductor absorber layer.