A solar cell utilizing a chalcopyrite semiconductor and reducing the density of defects on the junction interface of pn junctions is provided. This solar cell includes a substrate, a back electrode formed on the substrate, a p-type chalcopyrite semiconductor thin film formed on the back electrode, an n-type semiconductor thin film formed so as to constitute a pn junction with the p-type chalcopyrite semiconductor thin film, and a transparent electrode formed on the n-type semiconductor thin film. A material having a higher resistivity than the p-type chalcopyrite semiconductor is formed between the p-type chalcopyrite semiconductor thin film and the n-type semiconductor thin film. A thin film made of this material may be formed by deposition from a solution. For example, CuInS.sub.2 is formed on the surface of a p-type chalcopyrite based semiconductor such as CuInSe.sub.2 by contacting the surface of the semiconductor with a solution in which a salt containing group IIIb elements, an organic substance containing group VIb elements and acid are mixed.