Ultra-wideband solar absorber based on periodic slotted frustum arrays with wide-angle response

As a clean and renewable energy source, solar energy presents an effective solution to the current energy crisis and the challenges associated with climate change. The development of solar absorbers with near-perfect broadband absorption characteristics is critical for constructing high-efficiency solar energy harvesting systems, thereby advancing sustainable development. This study introduces an ultra-wideband tunable absorber based on a periodic slotted frustum structure. By innovatively integrating frustum units with periodic slotted configurations and conducting electromagnetic field simulation analysis using the finite element method (FEM), the influence mechanisms of structural parameters on the absorber’s performance are systematically investigated. Simulation results demonstrate that the absorber exhibits exceptional performance across an ultra-wide spectral range of 300–3000 nm, achieving an average absorption rate of 98.4% and a 90%-absorption bandwidth of 2700 nm. Furthermore, the structure exhibits polarization-insensitive behavior and maintains stable wide-angle absorption performance under large incident angles of up to 50°. Theoretical analysis based on impedance matching principles reveals that the broadband absorption results from the synergistic effects of multiple physical mechanisms including coupling between surface plasmon resonance and thin-film interference, the superposition of plasmonic resonance and Fabry–Pérot resonance, resonance enhancement in metal–insulator–metal (MIM) cavities, and the intrinsic light-absorbing properties of titanium. This research provides insights for the design of high-performance photothermal conversion devices.