Ti–Si 3 N 4 composite tower-like metasurface solar absorber with ultra-broadband high efficiency and superior thermal emission performance

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.