Ultra-broadband metamaterial absorber for capturing solar energy from visible to near infrared

Abstract

In this paper, a metamaterial absorber for broad-spectrum absorption under solar radiation is proposed, which consists of periodic square arrays on a-Si spacer layer and Ti substrate. With the coupling of multiple resonances, the average absorption of the absorber is more than 95% within the studied spectrum (300–2000 nm) and the bandwidth of absorption over 90% is 1576 nm (from 329 nm to 1905 nm). Since the Ti material in the absorber is a refractory metal with low cost and stable mechanical properties, the absorber can operate in high temperature environment. Especially, the study results show that the absorber has a general applicability to other refractory metals. Also, the absorber is insensitive to polarization and incident angles, which is very attractive in practical manufacture and use due to a high absorption performance within a large fabrication tolerance. In addition, the absorption spectrum of the absorber is highly consistent with the solar spectrum and can maintain a high integrated absorption at large incident angle. These findings show that the absorber has potential applications in many areas such as solar cells, solar energy harvesting, thermal emitters and photothermal conversion.