NOVELTY - A thin-film solar cell base structure is constructed by, forming a conductive protective film on front surface (102) of the stainless steel substrate (100) such that the conductive protective film substantially covers flat surface portions and partially leaves exposed some of protruded surface portions of the front surface; removing some of protruded surface portions by etching to form exposed substrate sections so that conductive protective film remains within the flat surface portions; and depositing contact layer (116) on conductive protective film and the exposed substrate sections.    USE - Method of constructing thin-film solar cell base structure (claimed).    ADVANTAGE - The method processes large volume roll-to-roll of copper indium gallium selenium solar cells and modules.    DETAILED DESCRIPTION - Construction of a thin-film solar cell base structure comprises:    (A) providing a stainless steel substrate (100) with a front surface (102) having substantially flat surface portions and protruded surface portions;    (B) forming a conductive protective film over the front surface of the stainless steel substrate such that the conductive protective film substantially covers the substantially flat surface portions and partially leaves exposed some of the protruded surface portions;    (C) removing some of the protruded surface portions by etching the protruded surface portions to form exposed substrate sections of the stainless steel substrate so that the conductive protective film remains within the substantially flat surface portions, where the conductive protective film is substantially resistant to the removing by etching; and    (D) depositing a contact layer (116) on the conductive protective film and the exposed substrate sections.    DESCRIPTION OF DRAWING(S) - The drawing is a schematic illustration of a structure with a substrate having surface roughness including protrusion and recesses, where a copper indium gallium selenium absorber layer and a transparent layer are formed on contact layer to form solar cell structure.    Stainless steel substrate (100)    Front surface (102)    Contact layer (116)    Absorber layer (118)    Transparent layer (120)