Extremely broadband light absorption by bismuth-based metamaterials involving hybrid resonances.

An ultra-broadband polarization-insensitive perfect absorber for the 400-4000 nm spectral range is proposed and studied. The absorber is composed of a dielectric film and a phase change material film sandwiched between a bismuth square ring array and a continuous bismuth mirror. Greater than 94% absorptivity across the wavelength range of 400-4000 nm and an averaged absorptivity of about 97% can be achieved. The physical origin results from the mixed effect of guided mode resonance (GMR), cavity resonance (CR) and surface plasmon resonance (SPR). In addition, such a property is maintained excellent in a very large viewing angle range. Furthermore, the proposed scheme exhibits certain geometrical parameter tolerance, which is beneficial for practical fabrication with low cost. Finally, the potential application of the solar cells is investigated as an illustration. The designed metamaterial absorber will find promising applications in solar cells, thermo-photovoltaics and detection.