Self-Driven Electrochromic Window System Cu/WO_x-Al³⁺/GR with Dynamic Optical Modulation and Static Graph Display Functions

Abstract

Electrochromic devices with unique advantages of electrical/optical bistability are highly desired for energy-saving and information storage applications. Here, we put forward a self-driven Al-ion electrochromic system, which utilizes WO x films, Cu foil, and graphite rod as electrochromic optical modulation and graph display electrodes, coloration potential supplying electrodes, and bleaching potential supplying electrodes, respectively. The inactive Cu electrode can not only realize the effective Al 3+ cation intercalation into electrochromic WO x electrodes but also eliminate the problem of metal anode consumption. The electrochromic WO x electrodes cycled in Al 3+ aqueous media exhibit a wide potential window (∼1.5 V), high coloration efficiency (36.0 cm 2 /C), and super-long-term cycle stability (>2000 cycles). The dynamic optical modulation and static graph display function can be achieved independently only by switching the electrode connection mode, thus bringing more features to this electrochromic system. For a large-area electrochromic system (10 × 10 cm 2 ), the absolute transmittance value in its color-neutral state can reach about 41% (27%) at 633 nm (780 nm) by connecting the Cu and WO x electrodes for 140 s. The original transparent state can be readily recovered by replacing the Cu foil with the graphite rod. This work throws light on next-generation electrochromic applications for optical/thermal modulation, privacy protection, and information display.

Multivalent-Ion versus Proton Insertion into Nanostructured Electrochromic WO3 from Mild Aqueous Electrolytes

“…The coloration efficiency values reported here are very close to those reported for other Zn-based smart window device operating with dual Zn 2+ /Al 3+ electrolytes and incorporating either a WO 3 electrode prepared by electrodeposition (η 633 = 54 cm 2 /C) or a Nb 18 W 16 O 93 cathode (η 633 = 45.28 cm 2 /C) . They are also similar to the value reported for the self-driven coloration of a sputtered WO x film in a Cu-based smart window containing an AlCl 3 aqueous electrolyte (η 633 = 36 cm 2 /C) . However, in all of these devices, the charge storage mechanism at the electrochromic cathode was attributed to the reversible insertion of Al 3+ , while here we unambiguously demonstrate that it relies on PICET.…”

“…29 They are also similar to the value reported for the self-driven coloration of a sputtered WO x film in a Cu-based smart window containing an AlCl 3 aqueous electrolyte (η 633 = 36 cm 2 /C). 49 However, in all of these devices, the charge storage mechanism at the electrochromic cathode was attributed to the reversible insertion of Al 3+ , while here we unambiguously demonstrate that it relies on PICET.…”

Machine learning-guided investigation for a high-performance electrochromic device based on ammonium metatungstate-iron(ii) chloride-heavy water electrochromic liquid

“…Note that the bleaching mechanism in our devices is different from that of conventional electrochromic devices where a reverse voltage is often required for oxidization. 38…”

Advances in multicolor electrochromic devices based on inorganic materials

“…Taking traditional EC devices as an example, replacing monovalent insertion ions (H + , Li + , and Na + ) with multivalent ions (e.g., Zn 2+ , Mg 2+ and Al 3+ ) is promising to improve the response speed and cycling stability of inorganic multicolor EC devices. [93][94][95][96][97][98][99][100][101] In addition, inorganic multicolor EC materials and devices need to be further cross-integrated with other advanced technologies to broaden the application scenarios. For instance, the multicolor EC smart window designed by integrating multicolor and dual-band EC properties can flexibly adjust the sunlight and heat of buildings, showing great potential in daily life applications.…”