A method of manufacture of CIGS photovoltaic cells and modules involves sequential deposition of copper indium gallium diselenide compounds in multiple thin sublayers to form a composite CIGS absorber layer of a desirable thickness greater than the thickness of each sublayer. In an embodiment, the method is adapted to roll-to-roll processing of CIGS PV cells. In an embodiment, the method is adapted to preparation of a CIGS absorber layer having graded composition through the layer. In a particular embodiment, the graded composition is enriched in copper at a base of the layer. In an embodiment, each CIGS sublayer is deposited by co-evaporation of copper, indium, gallium, and selenium which react in-situ to form CIGS.