Notched nanoring wideband absorber for total solar energy harvesting

Various methods for solar energy utilisation are being developed for reducing the emission of CO₂ from fossil fuels, and perfect solar absorbers are attracting increasing attention. In the present study, a metamaterial solar absorber is proposed. The absorber consists of an array of Ni notched nanorings that are periodically arranged on a gold substrate with a layer of SiO₂ dielectric between the rings. The proposed absorber achieves nearly perfect harvesting of incident solar energy, which is attributed to the integration of multiple modes of resonances from the notched nanorings on the top, including electric and magnetic polaritons. However, the composition, geometries, and arrangement of the notched nanorings significantly affect the absorption properties of our absorbers with a small tolerance. Additionally, the incident angle of light significantly affects the absorptance of our absorber because of the non-rotationally symmetric notched nanorings. When submerged in water, the absorbers that totally harvest solar energy can act as solar evaporators, which in turn promise potential applications involving solar vapour generation, sterilisation, and seawater treatment that can be enabled by solar energy for producing freshwater.