Optimizing the design of broadband solar metamaterial absorbers based on titanium nitride nanorings [Invited

Abstract

We propose a design rule for broadband metamaterial absorbers and investigate their plasmonic properties under solar irradiation. The metamaterials consist of periodic arrays of titanium nitride (TiN) rings placed on an antireflective MgF2 dielectric film on a TiN bottom layer. We simulate the absorption of our metamaterials and find the dependence of the optical spectrum on structural parameters. From this, we propose a simple rule to design the nanostructures with an average spectral absorptivity greater than 95% over the solar spectrum from 200 to 3000 nm. Particularly, we introduce, for the first time, metamaterial perfect absorbers that can be designed using two-layer structures instead of higher-layer structures as conventional and sandwich designs. Our study would pave the way for great potential applications in the fields of solar energy harvesters and photo-to-thermal converters.