Methods for forming a back contact on a thin film photovoltaic device are provided that include applying a conductive paste onto a surface defined by a p-type absorber layer (e.g., comprising cadmium telluride) of a p-n junction and curing the conductive paste to form a conductive coating on the surface defined by a p-type absorber layer of the p-n junction. The conductive paste can include a conductive material, a solvent system, and a binder such that during curing an acid from the conductive paste reacts to enrich the surface with tellurium while copper is deposited onto the Te enriched surface. The acid is then substantially consumed during curing.