Broadband polarization- and angle-insensitive metamaterial absorber based on a hexagonal web lattice with Ni-AlN-Ni tri-layer structure for enhanced solar energy harvesting.

Broadband metamaterial absorbers (MMAs) are widely explored for photonic applications, yet many designs exhibit limited visible-range efficiency or polarization sensitivity. This work presents a nickel-aluminum nitride-nickel (Ni-AlN-Ni) MMA with a hexagonal web lattice resonator with radial connectivity in a metal-insulator-metal configuration. Finite-element electromagnetic simulations show an average absorption of 98.1% over 150-1400 nm (vacuum ultraviolet to near-infrared). In the visible range (380-780 nm), the average absorption is 99.4%, with peak absorption of 99.95% at 570 nm. Unlike conventional multiring resonators, the hexagonal web lattice with radial connectivity introduces multiple hybridized plasmonic modes and suppresses polarization conversion, which collectively enable the achievement of near-unity visible absorption. The absorber maintains absorption above 90% for incident angles up to 60° and shows polarization insensitivity. For terrestrial solar energy harvesting under the AM1.5 spectrum (280-2500 nm), the weighted absorption efficiency is 96.5%, rising to 98.656% in the visible range. These simulated performance metrics indicate potential applications in solar energy harvesting, thermal emission control, optical sensing, stealth technologies, and photothermal catalytic applications.