Cyclic Al2O3-TiN stacked microstructures for broadband solar absorbers

To address the urgent demand for efficient solar energy harvesting, we propose a broadband absorber based on a simple stacked microstructure composed of Ti, Al₂O₃, and TiN. The designed structure features concentric Al₂O₃-TiN annular disks layered on a titanium substrate and demonstrates ultra-wideband absorption from 200 to 3201 nm, with an average absorptivity of 97.2 %. Finite-difference time-domain method reveals that the absorber maintains high efficiency across various incident and polarization angles, thanks to its symmetric geometry. Field distribution analyses confirm that the superior absorption performance arises from the synergistic effects of localized surface plasmon resonance and dielectric cavity resonance. Furthermore, the absorber exhibits excellent thermal radiation performance at 1000 K. These results indicate that it is well suited for use in solar thermal photovoltaic systems and has significant application potential in areas such as solar cells, solar collectors, thermal radiators, and photothermal conversion technology.