NOVELTY - A thin film solar cell (100) is formed by providing a metallic substrate (108) such that a finished front surface (106) of the metallic substrate has an average roughness of less than 50 nm and a conditioned back surface (105) that has an average roughness of more than 200 nm; and forming a Group IB-IIIA-VIA compound solar cell absorber layer (112) over the finished front surface.    USE - Method for forming a thin film solar cell used in manufacturing a solar module (claimed).    ADVANTAGE - The method can enhance adhesion at interfaces in the module structure formed using metal-foil based thin film solar cells; and enhance manufacturability and long term reliability of these modules.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for:    (1) a method of manufacturing a solar module comprising forming a string of solar cells, where the string of solar cells include at least two solar cells, and each solar cell includes a light receiving stack with an exposed top surface and a conductive substrate having a rough back surface and a finished front surface over which the light receiving stack is formed, where the light receiving stack includes a Group IB-IIIA-VIA absorber layer, and where the average roughness of the rough back surface is more than 500 nm and the average roughness of the finished front surface is less 50 nm; bonding a back packaging layer to the rough back surfaces of the conductive substrates and a front packaging layer to the exposed top surfaces of the light receiving stacks of the solar cells respectively;    (2) a method of attaching a contact lead to the back side of a solar cell structure, comprising laser treating a predetermined area of the back side of the solar cell structure forming a treated back surface area; and attaching the contact lead to the treated back surface area;    (3) a solar cell comprising a conductive substrate having a front surface and a back surface including roughness; and a Group IB-IIIA-VIA absorber layer formed over the front surface; and    (4) a solar cell module comprising a string of solar cells, a back packaging layer bonded to the rough back surfaces of the conductive substrates; and a front surface packaging layer bonded to the exposed top surfaces of the light receiving stacks.    DESCRIPTION OF DRAWING(S) - The drawing shows a side schematic cross-sectional view of two solar cells interconnected using the method for forming a thin film solar cell.    Thin film solar cell (100)    Conditioned back surface (105)    Finished front surface (106)    Substrate (108)    Solar cell absorber layer (112)