A titanium-based hollow-cube metamaterial for efficient broadband solar absorption

Broadband solar absorbers play a pivotal role in efficient solar thermal conversion and sustainable energy utilization. The proposed absorber design is based on a metal-dielectric-metal structure, featuring Ti metal for both the bottom and top layers, an Al₂O₃ dielectric for the intermediate layer, and a top resonator composed of a hollow square prism with corner notches. As demonstrated by finite difference time domain simulations, this structure achieves an average absorption rate that exceeds 90% across the 280-3138 nm wavelength range, exhibiting a solar-weighted absorption efficiency of 92.8%. It has been demonstrated to exhibit exceptional photothermal conversion efficiency and notable robustness against variations in polarization and incident angle. Theoretical analysis further explores the physical mechanisms underlying its broadband absorption. A comparison of this absorber with existing designs reveals its superior thermal stability and structural simplicity. This makes it suitable for solar energy harvesting, thermal radiation control, and integrated optoelectronic devices. This work presents a novel approach for developing refractory metal-based metamaterial absorbers and holds significant implications for advancing research on efficient solar energy utilization.