Ultra-Broadband Spectrally Selective Absorber for Solar Thermal Absorption Based on TiN Square-Ring Meta-Structure

Based on the TiN square-ring structure, a spectrally selective absorber for solar thermal absorption is proposed announcing an average absorption of 95.69% in the major solar spectral region (280 nm∼2500 nm). When the wavelength exceeds 2500 nm, the absorption declines rapidly and decreases to 40.4% at the wavelength of 4000 nm, showing excellent spectral selectivity. As the incident angle of TE or TM polarized wave varies in a range of 0∼60 degrees, the proposed absorber maintains more than 90% solar absorption efficiency, which proves the insensitivity of incident angle and polarization angle. With operating temperature T = 300 K and solar concentrating coefficient C = 1, the solar-thermal conversion efficiency of the proposed absorber is 93.92%. At a high temperature of 700 °C, the solar-thermal conversion efficiency can maintain more than 80% at the condition of C = 200, demonstrating good thermal tolerance. It is believed that the proposed absorber has great potential to be applied in solar thermal absorption systems.