Ultra-broadband Metamaterial Absorber for High Solar Thermal Energy Conversion Efficiency

In this paper, a titanium cross-shaped based-metamaterial absorber in the visible and near-infrared regions is presented. The proposed solar thermal absorber consists of a cross-shaped titanium/SiO2 spacer/TiN ground film structure enabling high broadband absorption and solar-thermal conversion efficiency. The broadband nearperfect absorption spectra with the proposed structure reach 97% for both TE and TM-polarization in the wavelength ranges of (from 386 to 1178 nm) and (from 300 to 1140 nm), respectively. Furthermore, the proposed structure exhibits a high solar thermal conversion efficiency of 96% under continuously variable of C from 1 to 1000, maintained over the wide operating temperature range 373-779 K. Remarkably, the performance of the structure has been promising for the enhancement of the solar thermal energy harvesting devices at middle to high temperatures.