An ultra-broadband polarization-independent perfect absorber for the solar spectrum

Abstract

We numerically investigated an ultra-broadband, polarization-insensitive, and wide-angle metamaterial absorber for harvesting solar energy using arrays of cascading three sets of subunit cell structures with obviously different lateral sizes, while each of the subunit cell structures is composed of three pairs of metal–dielectric layers with the same lateral sizes but different dielectric constants. In this structure, the varying lateral dimensions provide multiple resonance main-bands in the composite structure, while the different dielectric constants of the dielectric layers induce multiple resonance sub-bands in the subunit cell. Simulation results show that the average absorption over the spectrum regime of 284–1524 nm is more than 92%. Moreover, the ultra-broadband response above 92% absorption can be still maintained even when θ reaches 30 degrees. The ultra-broadband absorption obtained is attributed to the synthetic effect by the excitation of all resonances in the multiple resonant stacks of 3 × 3 cascading metal–dielectric pairs. Our absorber design has high practical feasibility and appears to be very promising for solar cell and photonic detection applications.