The present invention relates to a process for producing a layer comprising at least one semiconductive metal oxide on a substrate, comprising at least the steps of: (A) applying a porous layer of at least one semiconductive metal oxide to a substrate, (B) treating the porous layer from step (A) with a solution comprising at least one precursor compound of the semiconductive metal oxide, such that the pores of the porous layer are at least partly filled with this solution and (C) thermally treating the layer obtained in step (B) in order to convert the at least one precursor compound of the semiconductive metal oxide to the semiconductive metal oxide, wherein the at least one precursor compound of the at least one semiconductive metal oxide in step (B) is selected from the group consisting of carboxylates of mono-, di- or polycarboxylic acids having at least three carbon atoms or derivatives of mono-, di- or polycarboxylic acids, alkoxides, hydroxides, semicarbazides, carbamates, hydroxamates, isocyanates, amidines, amidrazones, urea derivatives, hydroxylamines, oximes, oximates, urethanes, ammonia, amines, phosphines, ammonium compounds, nitrates, nitrites or azides of the corresponding metal, and mixtures thereof.