NOVELTY - Forming a Group IB/IIIA/VIA compound layer on a base by: forming a precursor layer on the base, which involves electrodepositing a first film on the base using a first electrodeposition solution, the first film comprising a copper-indium-gallium ternary alloy; electrodepositing a second film on the metallic film using a second electrodeposition solution, the second film comprising one of a copper-selenium alloy, an indium-selenium alloy and a gallium-selenium alloy; and electroplating a third film comprising selenium on the second film; and reacting the precursor layer with selenium.    USE - For forming a Group IB/IIIA/VIA compound layer on a base (claimed) for preparing semiconductor thin films for photovoltaic cells or solar cells.    ADVANTAGE - The metallic films produced by the method is very beneficial to regulate the desirable reaction pathways in formation of copper indium gallium diselenide (CIGS) absorber layer. During the electrodeposition process, Cu electrodeposition may be encouraged by applying low plating potentials or current densities to produce the first portion. Therefore, at low plating potentials or current densities, the first portion of the metallic film will be rich in Cu. As the plating potential or current density is increased, more In and Ga will be incorporated into the film from the electrodeposition solution to form the second portion of the metallic film. The third portion of the metallic film grows under high electrodeposition potential with a low Cu amount high in In and Ga. The metallic films, which are produced this way, would be very beneficial to regulate the desirable reaction pathways in formation of CIGS absorber layer. The exclusion of Se in the Cu-Ga-In ternary electroplating solution provides several advantages. It allows utilization of high deposition rates for Cu-In-Ga layers. In fact, a large range of deposition current densities 1-60 mA/cm2 can be used for the Cu-Ga-In ternary electroplating solution. The film composition, morphology and the electrical conductivity and defectivity can be much better controlled when Se is excluded. Electrodeposition of subsequent thin film layers with minimal defectivity is possible over a high quality Cu-In-Ga thin layer.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for a precursor structure for forming a Group IB/IIIA/IVA solar cell absorber on a surface of a base, comprising a first alloy film formed on the surface of the base, the first alloy film comprising copper, indium and gallium, where the thickness of the first alloy film is at least 50 nm; a second alloy film comprising copper and selenium formed on the first alloy film; and a selenium film formed on the second alloy film.