Broadband visible to mid-infrared aluminum-black absorbers and the aging behavior

Broadband light absorbers are attractive for their applications in solar-energy harvesting, thermal detectors and photodetection. Metal-black absorbers have been experimentally proved having broadband light absorption and low mass density. Expensive gold and silver metal-black absorbers have shown excellent performances in various applications. Here, we present low-cost aluminum (Al) -black absorbers fabricated by thermal evaporation processes. The average absorption of Al-black coatings with evaporation time of 10, 20 and 30 s were 60.82%, 84.83% and 92.18% in 320–2500 nm spectral range and 92.82% (30 s) in 2.5–15 μm, demonstrating that Al-black films can be used as low-cost broadband light absorbers. Long-term stability of optical properties was a significant technological concern for metal-black absorbers. Therefore, room temperature aging behaviors of Al-black absorbers were investigated. Comparative analyses on morphological, atomic content, spectral absorption and photothermal response before and after 60 days and 120 days of room temperature aging of the Al-black absorbers were carried out. The aging of the Al-black films was attribute to the mechanical pressure and oxidation. The aged Al-black absorber exhibited similar absorption and time-dependent photothermal response characteristics as that before aging from visible to mid-infrared spectral range. These results indicated that the Al-black films possessed excellent stability of solar absorption and photothermal response after aging, which can be low-cost alternative absorbers of expensive metal-black films.