NOVELTY - Forming thin film photovoltaic device involves subjecting multi-layered structure to thermal treatment process (200) in environment containing sulfur bearing species (210); forming copper indium disulfide material (220) comprising thickness of copper sulfide material (221); removing thickness of copper sulfide material to expose surface region having copper poor surface; subjecting copper poor surface to metal cation species to convert copper poor surface from n-type to p-type semiconductor characteristic; and forming window layer overlying the disulfide material.    USE - For forming a thin film photovoltaic device (claimed), for high efficiency solar cell application; for converting electromagnetic radiation into electrical power.    ADVANTAGE - The method uses starting materials that are commercially available to form a thin film of semiconductor bearing material overlying a suitable substrate member. The thin film of semiconductor bearing material can be further processed to form a semiconductor thin film material of desired characteristics, such as atomic stoichiometry, impurity concentration, carrier concentration, doping. The band gap of the resulting copper indium disulfide material is 1.55 eV. Additionally, the present method uses environmentally friendly materials that are relatively less toxic than other thin-film photovoltaic materials. The method and resulting structure is free from a parasitic junction on an absorber layer based upon a copper poor chalcopyrite material.    DETAILED DESCRIPTION - Forming a thin film photovoltaic device involves providing a transparent substrate (110) comprising a surface region; forming a first electrode layer (120) overlying the surface region; forming a copper layer overlying first electrode layer; forming an indium layer overlying the copper layer to form a multi-layered structure; subjecting the multi-layered structure to a thermal treatment process (200) in an environment containing a sulfur bearing species (210); forming a copper indium disulfide material (220) from the thermal treatment process of the multi-layered structure, the copper indium disulfide material comprising a thickness of copper sulfide material (221) having a copper sulfide surface region; removing the thickness of the copper sulfide material to expose a surface region having a copper poor surface; subjecting the copper poor surface to a metal cation species to convert the copper poor surface from an n-type semiconductor characteristic to a p-type semiconductor characteristic; subjecting the copper poor surface to a treatment process during a time period associated with the subjecting of the copper poor surface with the metal cation species; and forming a window layer overlying the copper indium disulfide material.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of method for forming a thin film photovoltaic device.    Transparent substrate (110)    First electrode layer (120)    Thermal treatment process (200)    Sulfur bearing species (210)    Copper indium disulfide material (220)    Copper sulfide material (221)