Optimization of titanium-based ultra-broadband metamaterial absorbers for solar harvesting and thermophotonic applications

This work presents a titanium-based ultra-broadband metamaterial absorber for solar energy harvesting and thermal emission applications. The absorber comprises a periodic array of Ti resonators on a silica layer, followed by a tungsten substrate. Utilizing the particle swarm optimization algorithm, the structure achieves an average absorption of 96.21% over the 0.28–2.5 µm spectral range. Simulation results reveal near-unity absorption across the entire range, with three resonance peaks attributed to cavity modes, localized surface plasmons, and propagating surface plasmons. The absorber maintains high efficiency across different angles and polarizations, particularly with TM-polarized light, achieving over 90% absorption at incident angles of up to 64° and 45° for TE-polarized light. Solar absorption efficiency reaches 95.93% under AM1.5G illumination, while thermal emissivity remains above 96% at 1000–1500 K temperatures. The design exhibits strong tolerance to fabrication errors and outperforms comparable Ti-based absorbers in bandwidth and average efficiency. These features make it a promising candidate for solar and thermophotonic applications.