Solar photovoltaic (PV) devices, e.g., those based on the Copper Indium Selenide (CIS) family of absorbers, including CuIn(1-x)Ga(X)Se2 (CIGS) absorber thin-film PV devices, are provided. Embodiments provide PV devices comprising an alkali metal- containing polymeric film (ACPF), which is a film formed from a composite comprising an alkali metal-containing material and a polymer. Embodiments of this disclosure also provide PV devices comprising a thermally stable polymer film that does not contain an alkali metal (TSP). Included within the embodiments of this disclosure are flexible PV devices comprising a flexible base substrate onto which one or more ACPFs and/or TSPs is/are provided, as well as flexible PV devices wherein an ACPF or TSP itself constitutes the base substrate in the form of a stand alone film. Processes for making such flexible PV devices include roll-to-roll processes. PV devices disclosed herein will provide improved energy conversion efficiencies as a result of the delivery of sodium dopant into the absorber layer.