Metamaterial absorber with ultra-broadband, ultra-high absorption, polarization independence and high-temperature resistance for solar thermal energy harvesting applications

In this work, a metamaterial absorber with ultra-broadband, ultra-high absorption, polarization independence and high-temperature resistance for solar thermal energy harvesting applications is designed and numerically simulated. The proposed nanostructure is composed of four T-shaped strips and square ring nanoarray structures of tungsten (W) material deposited on Au substrate. The findings demonstrate that the solar metamaterial absorber can attain broadband absorption of solar energy with a bandwidth of 1.78 μm and the absorption rate of over 90% at the resonance wavelengths of 0.4 μm and 2.18 μm. Namely, the solar absorber exhibits excellent features of ultra-broadband and ultra-high absorption. The ultra-broadband and ultra-high absorption rate of solar absorbers are achieved by exciting surface plasmon resonance (SPR). In the design of solar absorber, the performance can be further enhanced by optimizing the geometry of the nanostructure (e.g., changing the geometric dimensions of T-shaped strips and square rings, and the period of array structures, etc.). Whether in TM mode or TE mode, solar metamaterial absorbers are insensitive to incident angles and can be used within the range of 0°–45° incident angles. The variation of the polarization angle also does not affect the absorption performance of the solar absorber with good polarization independence. Furthermore, at high temperatures from 300 °C to 1500 °C, the optical properties hardly change. It is found that the designed solar metamaterial absorber not only has ultra-broadband and ultra-high absorption, but also has excellent performance of polarization independence and high-temperature resistance. Consequently, this absorber has a promising application in solar cells, photothermal conversion and solar thermal energy harvesting applications.