Optical modeling of multilayered coatings based on SiC(N)H materials for their potential use as high-temperature solar selective absorbers

SiCH thin films grown from Ar/tetramethylsilane plasmas (PECVD) were evaluated as absorber layers in selective coatings for high-temperature solar receivers. SiCH coatings are used in thermomechanical applications because of their good thermal stability. A SiCH film with an absorption index k(430 nm)=0.11 was taken as a reference for optical simulations of refractory metal-SiCH multilayer stacks and cermets. The transfer matrix method and Maxwell-Garnett effective medium approximation were used to calculate the spectral reflectance and transmittance of the selective absorbers. Their solar absorptance and thermal emittance were also deduced. A seven-layer stack with alternating metal and SiCH layers was found to present a simulated solar absorptance of 0.92 and thermal emittance of 0.08 at 500 °C.