Optimizing the design of ultra-broadband perfect absorber based on hexagonal lattice of titanium (Ti) parabolic nanoarrays

Solar energy is a clean and renewable energy source that solves energy and climate emergencies. The near-perfect broadband solar absorbers can offer necessary technical assistance to follow this route and develop an effective solar energy-harvesting system. This work designed a metamaterial perfect absorber that operates in the ultraviolet to near-infrared spectral range. It is made up of titanium (Ti) parabolic nanoarrays with a hexagonal lattice structure. By using the commercially available 3D-electromagnetic simulator (Lumerical FDTD) operating in the finite-difference time-domain approach, we have found the strong absorption (⪆ 90%) of the absorber across the broadband range of the wavelength 200–3000 nm. Furthermore, we observed that increasing the height of nano-pillars can lead to an expansion in the bandwidth of the absorber. Our study highlights the significant roles played by the localized surface plasmon resonances of Ti parabolic nanoarrays, the inherent loss of titanium material, and the coupling of resonance modes between adjacent parabolic nanoarrays in facilitating this broadband perfect absorption phenomenon. Additionally, we demonstrate that the absorber exhibits some excellent features desirable for the practical absorption and harvesting of solar energy, such as precision tolerance, polarization independence, and large angular acceptance.