Temperature-induced degradation of bilayer MoOx-based solar absorbers under air annealing conditions

Abstract

Thermal stabilities of solar selective absorber coatings in operating environment are crucial to evaluate the durability, which are directly related to the optical properties. Degradation induced by temperature is an important guarantee for assessing long service life. Here, the sputtered bilayer MoOx cermet-based solar selective absorber coatings with an absorptance of 0.91 and an emittance of 0.06 are investigated under air annealing conditions. Thermal aging test shows no degradation of the MoOx/SiO2 absorber with a selectivity of 0.904/0.06 when annealing up to 250 °C for 200 h. In contrast, the MoOx/MoOx absorber shows significantly poor thermal tolerance at 200 °C in aerobic environment. As extending the temperatures and durations, the solar absorber is severely degraded owing to the diffusion and oxidation of Mo atoms induced by temperature, which is also responsible for the optical and structural deterioration of the absorber. These results highlight that the as-obtained absorber coatings have good possibility for solar thermal harvesting application.