Thin film multilayer design types for colored glazed thermal solar collectors

Multilayered interference filters of dielectric thin films have been designed for the application as energy-efficient coloration of collector cover glasses. The optical behavior of the designed multilayers is analyzed by computer simulations yielding the CIE color coordinates, the relative luminosity, the degree of solar transmission, and a figure of merit which is a measure for the energy effectiveness of the coloration. A high performance should be achieved with a number of individual layers reasonable for large-scale deposition. Constraints on the refractive index of the dielectric films are given by the availability of suitable thin film materials. The challenge lies in finding the best combination of material choice and layer thicknesses. We describe several types of multilayer designs for which the computer simulations yield promising results.