Towards coloured glazed thermal solar collectors

Multilayers of TiO2 and SiO2 dielectric coatings deposited by reactive sputtering have been characterized by X-ray photoelectron spectroscopy, in situ real-time laser reflectometry, spectroscopic ellipsometry and spectrophotometry. Measurements have been performed on individual dielectric layers of TiO2, SiO2 and multilayers. The experiments show a good agreement between the different techniques. Optical properties can be modelled properly using a Cauchy dispersion model. The optical constants of an individual layer are confirmed by the optical measurements on more complex multilayer structures. Reflectivity of the three-layer films fulfils the requirements for a first step towards coloured glazed thermal solar collectors.