Effect of surface roughening on increasingthe spectral selectivity of cermet solarselective absorbers

Abstract

Abstract The spectral selectivity of Cu–Al2O3 cermet solar absorbers was studied theoretically and experimentally in different layer designs. The results showed clearly that, by increasing the substrate temperature during film deposition, the desired random roughness features will be created on the surface of the cermet, which leads to higher selectivity. Theoretical simulation showed that a single cermet structure with the assistance of an anti-reflection layer, results in the best optical properties. Instead of such a structure, which is sensitive to fine thickness control, it was tried experimentally to increase the selectivity of a single cermet structure as much as possible using a roughness template layer. Surface roughening using such a layer design increased the solar absorptance from 0.840 to 0.956 while keeping the thermal emittance almost unchanged at about 0.028.