An ultra-high absorptivity solar absorber with excellent thermal radiation efficiency based on a metal-dielectric stacked structure.

Metamaterials hold great promise for application in the field of perfect absorbers due to their remarkable ability to manipulate electromagnetic waves. In this work, a full-spectrum ultra-wideband solar absorber with a multilayer metal-dielectric stacked structure is designed. Our absorber is simple and easy to manufacture, with Ti serving as the substrate, overlaid with SiN spacer layers and four pairs of Ti-SiN ring columns. It exhibits an average absorption rate of 98.48% from 280 to 4000 nm. The synergistic effects of cavity resonance (CR), surface plasmon resonance (SPR), and magnetic resonance (MR) effectively enhance the absorption performance. The impacts of different materials, stacked layers, and geometric parameters on the absorption performance are investigated, along with further analysis of the electromagnetic field distribution to study the physical mechanism for achieving high-efficiency absorption. Additionally, it is demonstrated that the absorber exhibits polarization-independent behavior under vertical incidence and maintains an average absorption rate of over 93% at a 50° incidence angle for transverse magnetic (TM) and transverse electric (TE) polarized light. Furthermore, the absorber achieves a total solar absorption rate of 98.07% across the entire spectrum, with a thermal radiation efficiency of over 99% and a photothermal conversion efficiency of 92.49% at 1000 K. To conclude, our absorber offers great possibilities for solar energy harvesting related applications.