design and analysis of ultra broadband nano-absorber for solar energy harvesting

In this paper, we propose a metamaterial based ultra broadband nano-absorber (ubna) for solar energy harvesting, whose elements consist of a ring column and dual hexagon pillar at the center. in this absorber, the light of shorter wavelengths is harvested at ring column, while the light of longer wavelengths is trapped by dual hexagon pillar. it is found that the average absorptivity of the ubna is as high as 96% in 300–1300 nm waveband and the ubna can maintain 95% in the whole visible and near-infrared waveband ranging from 300 to 2000 nm. in addition, the perfect light absorbing capability of the ubna is independent of the incident light polarization state in the waveband of 300–1300 nm, and it can keep up an average absorptivity of 91% with an large incident angle varying between −60° and 60°. we attribute the perfect absorbing property of ubna to the synergistic effect of the slow wave effect, fabry-perot resonance and the localized surface plasmon resonance enhancement.