A near-ideal solar selective absorber with strong broadband optical absorption from UV to NIR.

A near-ideal solar absorber, which is composed of a metal nanowire array and a planar multilayer system, is proposed and investigated. Both numerical and analytical results show that the proposed nanostructure can achieve over 90% optical absorption throughout the wavelength range of 300-1909 nm due to the coupled effect of multiple resonance modes, and can maintain a good absorption stability over a wide incident angle regardless of the polarization states. Meanwhile, for practical applications, the total photothermal conversion efficiency can reach 95.57% at operating temperature of 373.15 K, which is particularly useful in solar energy harvesting. The absorption performance is also strongly dependent on the diameter and height of nanowire as well as the thicknesses of dielectric layers, enabling the further improvement of both the operating bandwidth and absorption efficiency. Moreover, by adjusting the period of the multilayer or nanowire materials, the selective absorption properties of this nanostructure can be flexibly controlled to satisfy more spectral requirements. These features make the presented designs hold promise for a series of solar-dependent optical applications, such as photothermal energy generation and thermal emitters.