Ultra-wideband and wide-angle metamaterial absorber for solar energy harvesting from ultraviolet to near infrared

In this paper, an ultra-wideband solar absorber consisting of a four-layer structure of Al2O3-TiN-Al2O3-Ti is proposed. The proposed absorber achieves an average absorption of 97.85% in the wavelength range of 250-2000 nm (49.96% improvement over the reference planar structure), and its bandwidth of absorption over 90% is even as high as 1742 nm. As a result of the symmetrical design of the structure, the absorber has polarization insensitivity and wide-angle absorption characteristics. In particular, the absorber has a large process tolerance in the structural parameters and a high degree of universality for other metals and dielectric materials, which is highly advantageous in manufacturing. In addition, we explored the reasons for the high absorption of the structure in detail, discussed the influence of different structures on the absorption, and analyzed the absorption characteristics and thermal conversion efficiency of the structure under the solar spectrum. The proposed structure provides a broader bandwidth and higher light absorption than the recently reported work and further reduces the structure's thickness. Therefore, the absorber will have broad application prospects in photothermal conversion, solar cells, imaging, and stealth.