Ti-Si3N4 composite tower-like metasurface solar absorber with ultra-broadband high efficiency and superior thermal emission performance.

This study proposes a Ti-Si3N4 composite tower-like metasurface solar absorber designed for ultra-broadband, high-efficiency energy capture and high-temperature thermal emission. The physical mechanism relies on synergistic electromagnetic resonances-impedance matching, localized surface plasmon resonances, and Fabry-Perot cavity modes, which collectively extend photon pathways, suppress reflection, and enhance field confinement, enabling efficient energy dissipation via titanium's intrinsic optical loss. FDTD simulations show that the structure achieves an average absorption of 99.42% across 280-4000 nm, with a perfect absorption bandwidth (>90%) of 3597 nm and an absorption bandwidth exceeding 99% of 3045 nm. Under AM1.5 illumination, the weighted average absorption reaches 99.41%. Following Kirchhoff's law, it also exhibits exceptional thermal emission, reaching 99.72% efficiency at 1900 K, deviating by less than 0.3% from that of an ideal blackbody. Additionally, strong resonance coupling ensures excellent angle-insensitive and polarization-independent performance: average absorption remains 95.40% at incident angles up to 60°. This work offers a physically robust strategy for high-performance broadband solar absorbers and thermal emitters, with strong potential in photothermal conversion, thermophotovoltaics, and infrared detection.