Molybdenum (Mo) back contacts for CIGS solar cells

Mo metal back contacts for CIGS solar cells have been reviewed. The electrical resistivity, reflectance and adhesive properties of Mo thin films are affected strongly by the film deposition parameters. A Mo thin film with low resistivity and good adhesion can be obtained through two-step process. This bilayer Mo thin film can be formed through the different film structures depending on the working pressure. A MoSe2 layer formed at CIGS/Mo interface changes the CIGS/Mo hetero-contact from Schottky-type contact to ohmic-type contact. It also improves the adhesion between CIGS and Mo layers when its c-axis is parallel to the Mo surface. Additionally, it forms the back surface field for CIGS solar cells. However, the MoSe2 formation and c-axis orientation depend on the state of Mo prior to selenization, the medium of selenization, and the substrate temperature during selenization. At last, a single layer Mo thin film with low enough resistivity and good adhesion has been fabricated successfully by the pulse magnetron sputtering technology with appropriate deposition parameters.

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