An apparatus for sequential deposition of an intermixed thin film layer and a sublimated source material on a photovoltaic (PV) module substrate is provided, along with associated processes. The process can include introducing a substrate into a deposition chamber, wherein a window layer (e.g., a cadmium sulfide layer) is on a surface of the substrate. A sulfur-containing gas can be supplied to the deposition chamber. In addition, a source vapor can be supplied to the deposition chamber, wherein the source material comprises cadmium telluride. The sulfur-containing gas and the source vapor can be present within the deposition chamber to form an intermixed layer on the window layer. In one particular embodiment, for example, the intermixed layer generally can have an increasing tellurium concentration and decreasing sulfur concentration extending away from the window layer.