High temperature annealing effects on optical performance of TiAlN-based solar selective absorber with TiN IR reflector

Higher operating temperature of concentrating solar power plant could help to improving the solar-electricity conversion efficiency. However, solar selective absorber with stability higher than 700 °C is still lacking. Here, we explored the potential of a tandem structure absorber of TiN/Ti0.5Al0.5N/Ti0.33Al0.67N/CrAlSiO. The as-deposited tandem absorber had a solar selectivity of 0.887/0.134, which was maintained at 800 °C for 1 h. With the annealing temperature increasing from 800 °C to 1000 °C, the solar absorptance first slowly decreased from 0.887 to 0.866, then dramatically decreased to 0.7 after annealing at 1100 °C. Optical simulation indicated that thermal annealing would induced higher optical constants both for the Ti0.5Al0.5N and Ti0.33Al0.67N layers, which is caused by the spinodal decomposition of the cubic TiAlN phase. While the thermal emittance slightly increased from 0.134 to 0.154, as the TiN IR reflector maintained its layer structure even up to 1100 °C. •TiN/Ti0.5Al0.5N/Ti0.33Al0.67N/CrAlSiO solar absorber with a selectivity of 0.887/0.134 was stable at 800 °C for 1 h.•Higher annealing temperature induced phase decomposition in cubic TiAlN, and resulted in decrease of solar absorptance.•The absorber remained a low thermal emittance of 0.15 up to 1100 °C with TiN IR reflector.