Three dimensional compositional profile in CIS-based absorber layers of thin film solar cells

A solar cell comprising:

• a substrate;
• a back electrode layer disposed above the substrate;
• a buffer layer disposed above the back electrode layer;
• a window layer disposed above the buffer layer;
• and
• a Cu—In—Se-based absorber layer disposed between the back electrode layer and the buffer layer,
• wherein the Cu—In—Se-based absorber layer has a first surface, a second surface, a plurality of first regions and a plurality of second regions,
• wherein the plurality of first regions and the plurality of second regions have different compositional profiles from the first surface to the second surface,
• wherein, in each of the plurality of first regions and each of the plurality of second regions, the different compositional profiles are a gradient of an atomic ratio of Ga/(Ga+In) that increases from the first surface to the second surface.