High efficient and wide-angle solar absorption with a multilayered metal-dielectric film structure

A typical 6-layered metal-dielectric film structure of SiO2 (57.3 nm)/Cr (2.9 nm)/SiO2 (72.9 nm)/Cr (6.6 nm)/SiO2 (57.6 nm)/Cu (>100.0 nm) was designed and fabricated by magnetron sputtering. It showed a high solar absorption of about 95.8% in the wavelength range of 250-2000 nm, a low thermal emittance of about 0.104 at 600 K and good thermal stability at 673 K after annealing for 12 h in vacuum condition. The angle-dependent reflectance spectra indicated that the proposed 6-layered film structure has a great angular tolerance even when the incident angle increases to 50°. All of the excellent spectral properties and good thermal stability demonstrate the 6- layered planar film structure will be suitable for practical applications of solar-thermal conversion.