Ultra-broadband high solar absorption in checkerboard-shaped titanium nitride plasmonic metastructures

Titanium nitride (TiN) has been proved as an efficient, refractory plasmonic material in solar energy harvesting applications. In this paper, we demonstrate the design of a simple metastructure, including a checkerboard-shaped TiN grating layer embedded in a SiO2 dielectric layer and a TiN film as a reflective layer, to realize highly efficient light absorption for solar energy harvesting. After systematically optimizing the geometric parameters of the metastructure by finite-difference time-domain (FDTD) simulations, we achieve high absorption rates with an average value up to 97% across an ultra-broad spectral range from 0.4 to 2.0 μm, significantly extending the light absorption ranges reported in prior work. Detailed analyses of the electric field elucidate that the unique checkerboard-shaped pattern results in plasmon hybridization between the adjacent TiN nano-ribbons at different resonant wavelengths. Combined with the high absorption due to the dielectric-like nature of TiN and Fabry-Perot resonances, the proposed metadevice achieves excellent light absorption performance within the solar spectrum, exhibiting great potential for various solar energy harvesting applications.