An ultra-broadband and wide-angle absorber based on a TiN metamaterial for solar harvesting

The efficient absorption of solar spectrum radiation is the most critical step in solar thermal utilization. In this work, a near-perfect metamaterial solar absorber with broadband, wide angle, polarization insensitivity, and high-temperature resistance is proposed and investigated. The absorber takes advantage of the high melting point material, which consists of a TiN reflector, a SiO₂ insulating layer, and a TiN ring array. In the spectral range of 300-2500 nm, an average absorption of 97.6% is achieved. The percentage of absorbed energy in the AM1.5 spectral radiation can reach 95.8%. The electric and magnetic field distributions show that the high absorption is attributed to the coupling effect of surface plasmon resonance, guided mode resonance and cavity resonance. Furthermore, the absorber is found to maintain high absorption performance at large angles of solar radiation and to be insensitive to polarization. The designed absorber maintains its broadband absorption performance well within certain geometric tolerances. This reduces the complexity and cost of manufacturing and facilitates practical applications. The research indicates that this work will benefit the design and application of solar thermal conversion and thermophotovoltaic systems.