A simple process is disclosed for treating substrates having pre-structured zinc oxide layers on rigid or flexible supports. The ZnO is treated with an etching medium then with a cleaning liquid. The treatment with the etching and cleaning liquids is carried out while the substrate is conveyed through a device. The process is technically simple to implement and makes it possible to regularly and homogeneously roughen and texturize ZnO layers of up to 1 m2. The device for treating substrates having pre-structured zinc oxide layers on rigid or flexible supports has for that purpose a first means for treating the substrate with an etching liquid, a second means for treating the substrate with a cleaning liquid, and another means, in particular transport rollers, for conveying the substrate from the first to the second means.