NOVELTY - Method (I) of forming thin film photovoltaic device comprises: (a) providing transparent substrate (110); (b) forming first electrode layer (120); (c) forming copper layer on first electrode layer; (d) forming indium layer to form multi-layered structure; (e) subjecting multi-layered structure to thermal treatment in sulfur bearing species environment; (f) forming copper indium disulfide material (220) from the treatment; (g) subjecting portion of copper poor surface of copper indium disulfide material to copper species; and (h) forming window layer over copper indium disulfide material.    USE - The method is useful for forming thin film photovoltaic device (claimed), which are useful: in solar cell application; and for forming semiconducting thin films or multilayers.    ADVANTAGE - The method: utilizes environmental friendly materials that are relatively less toxic than other thin-film photovoltaic materials; and provides a thin film photovoltaic device, which is substantially free from a parasitic junction on an absorber layer based upon a copper poor chalcopyrite material.    DETAILED DESCRIPTION - Method (I) of forming a thin film photovoltaic device, comprises: (a) providing a transparent substrate (110) comprising a surface region (228); (b) forming a first electrode layer (120) overlying the surface region; (c) forming a copper layer overlying the first electrode layer; (d) forming an indium layer overlying the copper layer to form a multi-layered structure; (e) subjecting at least the multi-layered structure to a thermal treatment process in an environment containing a sulfur bearing species; (f) forming a copper indium disulfide material (220) from the treatment process of the multi-layered structure, where the copper indium disulfide material includes a copper poor surface; (g) subjecting at least a portion of the copper poor surface of copper indium disulfide material to a copper species; and (h) forming a window layer overlying the copper indium disulfide material. INDEPENDENT CLAIMS are also included for:    (1) method (II) for forming a thin film photovoltaic device, comprising: providing a substrate comprising a surface region; step (b) as above per se; forming a copper indium material by at least sputtering a target comprising an indium copper material; subjecting the copper indium material to a thermal treatment process in an environment including a sulfur bearing species; forming a copper poor indium disulfide material from at least the thermal treatment process of the copper poor indium material; compensating for the lack of copper in the copper poor copper indium disulfide material using a copper species; and step (h) as above per se; and    (2) method (III) for forming a thin film photovoltaic device, comprising: steps (a)-(b) as above per se; forming a chalcopyrite material overlying the electrode layer, where the chalcopyrite material includes a copper indium disulfide region; altering a characteristic of the copper indium disulfide region using a copper species; forming a window layer overlying the chalcopyrite material; and forming a second electrode layer overlying the window layer.    DESCRIPTION OF DRAWING(S) - The figure shows schematic diagram illustrating an method and structure for forming a thin film photovoltaic device.    Substrate (110)    Electrode layer (120)    Copper indium disulfide material (220)    Surface region (228)    Solution of potassium cyanide (310)