A method of making thermodynamically stable, diffusion-impeded barrier layers within, for example, a photovoltaic cell with a metal-containing electrical contact using exposure to fluorine. Exposing the cadmium telluride surface to fluorine creates a Te-poor barrier layer of cadmium fluoride. Once that barrier layer is formed, the metal-containing electrical contact may be applied or formed. The barrier layer allows tunneling current to occur between the p-type layer and the metal-containing electrical contact establishing a low-resistance, highly uniform, and thermally stable electrical contact.