TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Process: The process (M1), after the step (C) involves: transferring the transparent substrate including the indium layer overlying the copper layer to a second chamber without breaking vacuum between the first chamber and the second chamber to maintain the copper gallium layer and indium layer free from moisture; and maintaining the transparent substrate including the composite film to an environment free from moisture. The environment comprises dry air or dry nitrogen. The first electrode layer comprises a bi-layer molybdenum material. The chalcopyrite absorber layer comprises a compound semiconductor of CuInSe2 (CIS), CuIn(Ga)Se2 (CIGS), or CuIn(Ga)S2 with sodium doping. The chalcopyrite absorber layer comprises sodium with an average atomic density of about 5x 1019 atoms/cm3 throughout the absorber layer after thermal treatment process. The thermal treatment process is performed at a temperature ramping up from room temperature to above 500 degrees C, in a fluidic selenide or fluidic sulfide environment, preferably within a diffusion furnace. The transparent substrate comprises a soda lime glass substrate. The first sputtering process can be performed after the second sputtering process so that the copper and gallium layer overlays the indium layer. The third sputtering process can be performed after the second sputtering process followed by the first sputtering so that the sodium bearing species is formed between the indium layer and the copper and gallium layer. The third sputtering process uses a sodium bearing target with a uniform composition of the sodium species distributed within a host material. The first, second, and the third sputtering process are carried out in a same chamber but different compartments. The processing of the photovoltaic material involves: providing a substrate having an overlying molybdenum layer; forming a sodium bearing layer overlying the molybdenum layer; forming a precursor layer comprising copper, gallium, and indium overlying the sodium bearing layer; and subjecting the precursor layer to a thermal treatment process to form a photovoltaic absorber layer comprising a chalcopyrite structure bearing with copper, indium, gallium, and sodium. The substrate is a smooth plate. Forming the sodium bearing layer is performed by sputtering on a target bearing Na2SeO3 with total 8% of sodium mixed with copper and gallium. Subjecting the precursor layer to a thermal treatment involves ramping up process temperature to 500 degrees C within a gaseous environment containing selenium. EXAMPLE - No suitable example is given.