Infrared-Emissivity-Regulating Electrochromic Device with Low Visible Wavelength Absorption Based on Nanolayered Au/NiO/Ta2O5/WO3/Ge Photonic Structures

Dual-band electrochromic coupling is a phenomenon in which an electrochromic material can modulate the visible and infrared (IR) light spectra simultaneously. Due to their coupling of visible and IR wavelengths, high solar absorptivity, and low IR emissivity modulation, the application of all-solid-state electrochromic devices (ECDs) to space technology has become a great challenge. Here, a nanomultilayer optical simulation structure of ECDs was built to solve the above problem. In this study, the IR emissivity of ECDs (F–P ECDs) with a nanostructure of Au/NiO/Ta2O5/WO3/Ge is studied in detail via a Fabry–Perot resonance. The result shows that the IR emissivity regulating the ability of F–P ECDs is approximately 0.53 in the spectral range of 2–14 μm, with a maximum of 0.62 at 9.8 μm. To improve the IR emissivity modulation ability and solar radiation reflectivity as much as possible, a metamaterial structure (alternating deposition of ZnS and YbF3) is applied to F–P ECDs. The nanostructure, Au/NiO/Ta2O5/WO3/Ge/Metamaterials (M-ECDs), is studied in detail. The results show that the IR emissivity modulation of M-ECDs is approximately 0.72 in the spectral range of 2–14 μm, with a maximum of 0.87 at 10.5 μm. At the same time, M-ECDs can reflect 90.5% of solar radiation in the spectral range of 300–1500 nm. On the basis of these results, it is believed that the Fabry–Perot resonance and metamaterials provide a promising opportunity for future space technology.