NOVELTY - Liquid coating composition (LCC) containing group IIB and group VIA ionic species and complexing agent is applied onto a heated substrate surface at higher temperature than the temperature of the LCC. The group IIB and group VIA ionic species are reacted by complexing agent on the heated substrate surface to form a solid reaction product film on the substrate.    USE - For forming ultra thin semiconductor films for solar cells (claimed), for forming window layers for thin film solar cells and for manufacturing photovoltaic solar cell devices.    ADVANTAGE - The liquid coating composition is maintained at a lower temperature than the substrate surface prior to deposition to prevent the occurrence of homogeneous reactions in the bath, thus reducing particulate formation in the liquid composition. Keeping the solution at low temperatures of 5-25 degrees C ensures a reasonably long shelf life due to reduction of species evaporation and reduction of reaction rate leading to the onset of homogeneous nucleation in the solution. Non-uniformities and inclusions of secondary products in and on the film are prevented by avoiding the drying of the solid reaction product film during reaction. The films formed exhibit low particulate density and high utilization of the Group IIB species. The formation method provides high quality and ultra-thin films which are amenable to large area manufacturing of photovoltaic solar cell devices.    DETAILED DESCRIPTION - A liquid coating composition (LCC) containing group IIB and group VIA ionic species and complexing agent is applied onto a heated substrate surface at higher temperature than the temperature of the LCC. The group IIB and group VIA ionic species are reacted by complexing agent on the heated substrate surface to form a solid reaction product film on the substrate surface. The complexing agent causes the reaction of group IIB and group VIA ionic species under favorable conditions on the heated substrate. The product film contains a reduced form of group IIB and group VIA ionic species. INDEPENDENT CLAIMS are included for:    (a) formation of a solar cell; and    (b) solar cell formed by using the formed film on the substrate surface.    DESCRIPTION OF DRAWING(S) - The figure shows a flow chart indicating formation of a film on a substrate.