Super-hydrophilic and solar-heat-reflective coatings for smart windows

Hydrophilic and solar-heat-reflective coatings were deposited on glass substrates by radio-frequency sputtering. This bifunctional coating was a multilayer film consisting of SiO₂, TiO₂, and a heat-resistant silver alloy, which was used instead of pure silver. The multilayer film was used to improve the spectral reflection and spectral transmission properties. The heat-resistant silver alloy developed in this study facilitated the formation of an anatase layer on the surface of the coating at elevated temperatures. The photocatalytic anatase layer made the surface hydrophilic. The hydrophilic and optical properties of samples prepared at various temperatures were determined. Under ultraviolet irradiation, the water contact angle decreased from around 60° to 6° for a sample with an anatase surface layer. The sample glass reflected most of the infrared light and simultaneously transmitted visible light. - Highlights: ► Multilayer coatings for hydrophilic and solar-heat-reflective functions on glass ► Thin, heat-resistant silver alloy layer facilitated the formation of anatase. ► Photo-induced hydrophilicity was achieved using a top anatase layer. ► Drastic drop of water contact angle under UV irradiation obtained for some samples ► Excellent spectral selectivity of the TiO₂/SiO₂/Ag alloy/SiO₂/Ag coating for daylight