Photocatalytically active multi-layer systems with enhanced transmission

Photocatalytically active TiO2-films show a high reflectivity, this makes them inapplicable for use in self-cleaning solar cover sheets. To resolve this problem, an antireflective system with a top coat of SnO2 is used. Glass samples coated with such a layer system have a better transmission than commercially available self-cleaning glasses. A composition with SiO2 barrier/TiO2 underlayer/SnO2 top layer presents better degradation rates than pure TiO2 with a barrier layer. The 3-layer system also possesses lower water contact angles after irradiation and a prolonged hydrophilicity. The properties of the layer system depend on the partial oxygen pressure used during the reactive sputtering of the TiO2 film and the thickness of the TiO2-layer as well as of the SnO2-layer