Precisely nanofabricated cross shaped metamaterial absorbers for nearly perfect solar energy harvesting

Perfect solar energy absorption is becoming more and more significant in the fields of carbon neutrality, the numerical study of various metamaterial solar absorbers is boosting but their fabrication is still challenging us a lot. In this study, we propose a unique type of metamaterial absorbers with cross shaped nanostructures achieving efficient absorptance in the wavelength range of 300–2400 nm with an equivalent solar energy absorption efficiency up to 0.94. In addition, the proposed solar absorber is fabricated by using electron beam lithography (EBL) method, and its nearly perfect absorption properties affected by morphology and geometric parameters are further experimentally studied. We also numerically study the effects of the material compositions, geometrical parameters and light sources on the absorption properties of the broadband metamaterial absorbers, and the absorption mechanisms are revealed by employing the electric field distributions. The results indicate that the nearly perfect absorption of solar energy of our metamaterials mainly depends on the surface plasmon resonances (SPRs) that occur between sub-wavelength nanostructures. The present metamaterial solar absorber enables the promising applications of solar vapor generation, solar desalination, wastewater treatment, thermophotovoltaic, etc., especially those working in high temperature and harsh environments because of the high melting point of titanium used in it.