Optical properties and thermal stability of colored solar selective absorbing coatings with double-layer antireflection coatings

Multilayer solar selective absorbing coatings of Cu/Ti/SiO2/Ti/TiO2/SiO2 were designed first and then deposited on quartz substrates using the magnetron sputtering method. The thicknesses of the individual layers were optimized to achieve high solar absorptance, while the colors were designed with the TFCalc optical design software. The colors of the coatings including purple, blue, blue green, yellow green and orange yellow were prepared based on the designed parameter. The colored solar selective absorbing coatings exhibit solar absorptance higher than 0.95 and thermal emissivity lower than 0.09 at 80 °C. Furthermore, the thermal stability of the Cu/Ti/SiO2/Ti/TiO2/SiO2 coatings was studied by annealing at high temperature in vacuum and in air for 2 h. The X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy and spectrophotometry were used to characterize properties of the coatings. The results showed that the multilayer solar selective absorbing coatings were thermally stable at 450 °C in vacuum and 300 °C in air for 2 h, which may provide an instruction to design and fabricate high performance colored solar selective absorbing coatings.