Solar Selective Absorbers Consisting of Semiconducting Silicide Absorbing Layers with Thermally Stabilized Ag Base

摘要

Solar selective absorber coatings consisting of semiconducting β-FeSi_2 and thermally-stabilized Ag base have been fabricated for high temperature thermal energy conversion below 650 °C. The band gap of the β-FeSi_2 around 0.8 eV was suitable for absorbing solar radiation, and the high refractive index was gradually declined to the top surface by composing with SiO_2. The Ag base for suppressing infrared radiation loss was thermally stabilized by adding SiN_x nanoparticles and laminating with W layers. In-situ high temperature measurements of optical constants (refractive index n and extinction coefficient k) for each composing layer were carried out, and the temperature dependence of absorptance spectra for the multilayers were simulated based on the n and k spectra. The derived absorptance spectra showed that the developed multilayers achieved highly efficient solar-thermal energy conversion of above 78% below 650 °C.