Photonic Cooler Based on Multistacked Thin Films with Near-Infrared Filter Properties

We report on the development of a multistacked configuration of a photonic cooler for implementation in sunny and arid regions. The optimized multistacking structure considers TiOx as a top layer, NiOx as the buffer layer, and Ag as a hot mirror (i.e., a reflective layer of the NIR light spectrum). The entire stacked layers were deposited in situ without breaking the vacuum. The oxide layers were grown reactively under an oxygen medium at a deposition pressure of 2 × 10-4 Torr. The level of TiOx surface wettability was demonstrated to be controlled by the oxygen flow during the film growth process, which may additionally provide a self-cleaning property to the IR filters. By combining low refractive index layers (i.e., TiOx) with the high refractive index of the metal oxides (i.e., NiOx) along with the metal layers (i.e., Ag, Al), the photonic filtration (i.e., cutoff) of the infrared spectrum was successfully achieved while keeping the light transmittance of the visible (vis) light above 50%. Different structures with different thicknesses have been systematically assessed, including TiOx/NiOx/Ag, TiOx/NiOx/Al, TiOx/MoOx/Ag, and TiOx/MoOx/Al. Furthermore, numerical simulations were carried out using SCAPS-1D and OptiLayer software to evaluate the application of these filters on silicon solar cells, considering the experimental electrical and optical parameters for each explicit layer of the device. Our results confirm that the development of such coatings with a scalable thin film growth process may have a real commercialization potential due to their multifunctionalities such as IR filtering, antireflection coating in the vis range, and antisoiling properties.