Annealing enhanced optical performances of nano-multilayered TiAlN/AlCrSiN-based solar selective absorber

Solar selective absorber is an important component to improve the solar thermal conversion efficiency of next-generation concentrated solar power with working temperature higher than 700 °C. However, the selective absorbers with thermal stability up to 700 °C are still lacking. Here, we designed a solar selective absorber based on nano-multilayered TiAlN/AlCrSiN films via thermal annealing, which could induce spinodal decomposition in TiAlN layer and form dual phase structure of Ti-rich and Al-rich cubic-TiAlN, to enhance the optical performances and thermal stability of the absorber. The obtained absorber after annealed at 900 °C exhibited a solar absorptance of 0.923 and a thermal emittance of 0.192, as well as small variation (0.935/0.232) after annealing at 700 °C for 100 h. However, after annealing the absorber at temperatures higher than 1000 °C, the N-loss induced the formation of metal CrSi2 phase and obviously decreased the absorption in near-infrared region. These results indicated the potential of the implement of spinodal decomposition to construct solar selective absorbers with high performances.