Enhanced thermal stability of solar selective absorber based on nano-multilayered AlCrSiO films

Solar selective absorbers are excellent candidates to improve the solar thermal conversion efficiency. However, the absorbers with thermal stability at high working temperatures are still lacking. Here, we reported a solar selective absorber based on nano-multilayered AlCrSiO films synthesized by a cathodic arc ion plating system. The absorber, consisted of a TiN IR reflective layer, two nano-multilayered AlCrSiO films, and a top amorphous oxide AlCrSiO layer, had high absorptance of 0.923-0.927 and low emittance of 0.160-0.193. To study the high temperature thermal stability, the absorber was annealed at 600-700 degrees C in air for 200 h. The variations in the optical performances and microstructures of the annealed absorber were characterized by UV-Vis-near IR spectrophotometer, FTIR, TEM, SEM, EDS, XRD, and Raman. The results indicated that the absorber had a thermal stability with a selectivity of 0.923/0.161 up to 650 degrees C in air for 200 h. The nano-multilayered structure of AlCrSiO films was highly stable when annealed at 650 degrees C. The amorphous AlCrSiO layer could form a dense oxide layer capping on the absorber surface, effectively limiting the oxygen diffusion into the inter absorber. Therefore, the AlCrSiO-based solar selective absorber with excellent thermal stability could be possibly applied to high temperature solar thermal conversion.