Ultra-broadband high-efficiency solar absorber based on Ti-GaAs-Au structure for UV to near-infrared spectral range

In this study, we propose an ultra-broadband solar absorber composed of a trapezoidal base, an outer circular ring, and four nano-cylinders. The absorber has a covered bandwidth range of 300–4000 nm and a temperature range of 373–973 K. The average absorptance within the mentioned wavelength range is over 96.52%, and the efficiency of solar energy thermal conversion is above 0.9 at 373–973 K under a solar concentration factor of 1000, with a maximum efficiency of 0.9644. Analysis of its absorption mechanism using the finite-difference time-domain method indicates that the proposed solar absorber’s outstanding absorption performance is due to the excitation of surface plasmon polaritons, localized surface plasmon resonances, and cavity resonances enhanced electromagnetic fields. This result has also been validated by the impedance matching theory. Moreover, the proposed solar absorber exhibits insensitivity to different polarization angles and maintains a high absorption effect in the range of 0°–70° incidence angle. The designed solar absorber has potential applications in areas such as seawater purification, wastewater treatment, and steam power generation systems.