Improvement on solar selective absorption properties of anodic aluminum oxide photonic crystal films by electrodeposition of silver

Solar selective absorption films based on anodic aluminum oxide (AAO) photonic crystals were prepared by an anodization under periodic current-pulses, subsequently with an alternating current electrodeposition of Co and Ag in sequence. The phase structure, microstructure, and solar selective absorption properties of the Co-Ag electrodeposited film were investigated in comparison with a Co electrodeposited counterpart. Moreover, the stability of the properties against thermal annealing was examined for the two films. A one-dimensional photonic crystal structure was verified for the AAO part in both films, with the first-order photonic bandgap occurring at around 4 mu m, while the metals were confirmed to be deposited at the bottom of the AAO part in the form of nanoparticles. For the Co-Ag electrodeposited film, the Ag nanoparticles were deposited over those of Co. The Ag electrodeposition not only was contributive to the solar selective absorption properties, but also substantially improved the stability of the properties against thermal annealing. The Co-Ag electrodeposited film exhibited an infrared emissivity of 0.12, a solar absorptivity of 0.94, and a spectral selectivity of 7.83 before experiencing thermal annealing, while retained a decent spectral selectivity of 6.00 after being annealed in air at 300 degrees C for 24 h.