NOVELTY - Method (M1) of sodium doping in fabricating copper indium gallium diselenide species/copper indium diselenide species (CIGS/CIS) based thin film solar cells, comprises: providing (1010) non-planar shaped substrate member having surface region in first chamber having at least one target; forming (1020) barrier layer on surface region; forming (1030) first electrode layer; sputtering sodium bearing layer; forming precursor layer on sodium bearing layer; loading (1060) shaped substrate member in second chamber; and subjecting shaped substrate member to thermal treatment process in second chamber.    USE - The method is useful for sodium doping in fabricating CIGS/CIS based thin film solar cells (claimed) including cylindrical/tubular photovoltaic modules, non-planar surfaces, flexible sheets, plastics, building or window glass, roof tiles and automobiles.    DETAILED DESCRIPTION - Method (M1) sodium doping in fabricating copper indium gallium diselenide species/copper indium diselenide species (CIGS/CIS) based thin film solar cells, comprises: providing (1010) a non-planar shaped substrate member, having a surface region, in a first chamber which includes at least one target, where the shaped substrate member is configured through mechanical motions to allow the surface region to be exposed to at least one target; forming (1020) a barrier layer over the surface region; forming (1030) a first electrode layer over the barrier layer; sputtering a sodium bearing layer over the first electrode layer, where the sodium bearing layer includes a first amount of a sodium species; forming a precursor layer over the sodium bearing layer, the precursor layer including at least a copper or copper-gallium layer followed by an indium layer, where a content ratio of copper/group III species are no larger than 1; loading (1060) the shaped substrate member into a second chamber; and subjecting the shaped substrate member to a thermal treatment process in the second chamber to an environment including a gas-phase selenium species followed by a gas-phase sulfur species with the selenium species being removed, to form an absorber layer, where the gas-phase sulfur species comprises hydrogen sulfide released into the second chamber after the selenium species is removed from the second chamber before the temperature is further increased to 500 degrees C. An INDEPENDENT CLAIM is also included for a method (M2) of sodium doping in fabricating CIGS/CIS based thin film solar cells, comprising: providing the shaped substrate member; forming the barrier layer over the surface region; sputtering a first electrode layer including molybdenum over the barrier layer; sputtering a sodium bearing layer over the first electrode layer from a target which includes molybdenum and a sodium species; sputtering a first precursor layer over the sodium bearing layer from a target including copper and/or a gallium species; sputtering a second precursor layer over the first precursor layer from another target including an indium species; transferring the shaped substrate member including the first electrode layer, the sodium bearing layer, the first precursor layer, and the second precursor layer to a second chamber without breaking vacuum between the first chamber and the second chamber to maintain the copper and/or gallium layer and indium layer free from moisture; and subjecting the shaped substrate member to the thermal treatment process in the second chamber within an environment comprising gas-phase selenium species and gas phase sulfur species to form an absorber layer, where the thermal treatment process comprises a step of removing gas-phase selenium species replaced with a hydrogen sulfide gas in the second chamber before the temperature is ramped up to 500 degrees C.    DESCRIPTION OF DRAWING(S) - The figure shows a simplified flowchart illustrating a method of sodium doping in fabricating a CIGS/CIS thin film photovoltaic cell on a shaped substrate.    Providing shaped substrate member having surface region in first chamber (1010)    Forming barrier layer overlying surface region (1020)    Forming first electrode layer overlying barrier layer (1030)    Forming sodium bearing layer overlying first electrode layer (1040)    Transferring shaped substrate member to second chamber (1060)