Electrochromic materials from the visible to the infrared region: an example WO3

Abstract

Herein, the example of the most typical electrochromic material, namely WO 3 , is used to illustrate the potential of electrochromic materials for controlling infrared reflectance and hence, emissivity. Playing with various growth parameters, contrast in reflectance between the inserted H x WO 3 and deinserted WO 3 states as high as 73% in mid-wavelength band (MW, 3-5 μm) was achieved for 320 nm WO 3 films. The latter electrochromic materials were radio frequency sputtered on Au substrate at ambient temperature in 6 Pa of chamber pressure. In comparison, for long wavelength band (LW,(8)(9)(10)(11)(12), the contrast in reflectance did not exceed 30%. The origins of the various electrochromic behaviours are correlated to the film structure, morphology and composition, indicating better properties for porous, nonstoichiometric films.

Multistage Coloring Electrochromic Device Based on TiO2 Nanotube Arrays Modified with WO3 Nanoparticles

“…Electrochromic materials have been proved especially useful for smart windows, large‐area information‐displays, rear‐view mirrors for automobiles, energy saving, etc 1–4. The cation intercalation leads to additional electronic states in the bandgap of the materials, which in turn affects a change in the optical properties of the material causing light absorption in the visible spectral range.…”

Li4Ti5O12: A Visible‐to‐Infrared Broadband Electrochromic Material for Optical and Thermal Management

“…Besides the super‐broadband optical tunability of LTO, device design is also important for a functional electrochromic device. Effective designs for infrared electrochromism with metal substrates have previously been reported in the literature . Here, a proof‐of‐concept of the design shown in Figure f is demonstrated in Figure S8 (Supporting Information).…”

“…Such a device would not have leakage issues, and be operable at temperatures beyond the range of existing aqueous designs. [5,7a,8,21] While this study focuses on material properties, further work on in situ electrochromic switching of Li 4 Ti 5 O 12 remains to be done for device applications.…”

“…Devices based on such materials typically show tunabilities of emittance (Δε) ≲ 0.3 in the MWIR and LWIR ATWs. [6a,7] Two outliers are H x WO 3 ‐based devices (with Δε MWIR ≈ 0.7 and Δε LWIR ≈ 0.15–0.25) and poly(aniline)‐based electrochromic skins (with super‐broadband IR Δε ≈ 0.5) . However, the use of aqueous H + and polymers could prevent their application at high temperatures.…”

Electrochromic properties of WO3 as a single layer and in a full device: From the visible to the infrared

“…Earlier studies indicated a strong dependence of the evolution of the reflectance with the depositions conditions and in particular with the oxygen pressure for RFS-WO 3 thin films [7]. Fixing the pressure to its optimized value, namely 45 mTorr, for both FTO and Au substrates, an increase in film thickness leads to an increase of the optical modulation in the LW band (Table 1).…”