Application of nickel oxide thin films in NiO/Ag multilayer energy-efficient coatings

Energy-efficient coatings based on transparent heat mirrors are reported. These coatings are spectrally selective in that they transmit light and reflect heat in the form of infrared radiation, and thus save energy in buildings. In this work, these coatings were achieved by depositing a two-layer structure consisting of nickel oxide deposited on silver by thermal evaporation. First, the structural, chemical, and optical properties of nickel oxide thin films, that are relevant to their use in transparent heat mirrors, were investigated. This was achieved through x-ray diffraction, atomic force microscopy, x-ray photoelectron spectroscopy, and spectrophotometric characterization. Then, the optical properties of the two-layer structure were determined. Their performance was evaluated through integrated spectral quantities over the solar and visible ranges. Moreover, chemical depth profiling was carried out to investigate the spatial distribution of the elements among the layers. The deposited heat mirrors were found to exhibit the desired behavior of high visible transparency and high infrared reflection.