Enhanced spectral absorption of bilayer WOx/SiO2 solar selective absorber coatings via low vacuum pre-annealing

Abstract

Solar selective absorber coatings (SSACs) have been one of promising strategies for conversing solar radiation into heat source. To enhance the solar absorption properties, various strategies have been developed to fabricate the SSACs, involving multilayer structure, texturing surface, metal nitrides and carbides, etc., whereas these often entailed sophisticated processes and expensive material costs. Therefore, developing the simple method to yield platforms with excellent optical properties is highly desired. Here, we showed a simple and effective method to boost the optical absorptivity, namely low vacuum pre-annealing process. The resulting absorptance of WOx/SiO2 SSACs is significantly raised from 0.91 to 0.93, and the emittance remains around 0.055 only after annealing at below 300 °C for 10 h. The optical absorptivity of the pre-annealing SSAC is on par with most of absorbers, and it still remained excellent thermal stability in high-vacuum at 400 °C. This simple and efficient method could be a prospective strategy for booting the spectral absorption in the design of the desirable SSACs.