Highly Crystalline WO₃ Thin Films with Ordered 3D Mesoporosity and Improved Electrochromic Performance

Abstract

WO3 thin layers with nanometer-scale periodicity were prepared by evaporation-induced self-assembly (EISA) using a novel amphiphilic block-copolymer template (poly(ethylene-co-butylene)-block-poly(ethylene oxide)). The evolution of the mesoporous ordered network and the crystallinity of the framework were monitored by 2D-SAXS, WAXS, SEM, XPS, and porosimetry. By annealing the films, the pore-wall crystallinity is adjusted between fully amorphous and highly crystalline without mesostructural degradation. Thus, the crystalline-film framework is composed of phase-pure monoclinic WO3 nanoparticles (12-14 nm in size). Furthermore, heat treatment transforms the originally spherical mesopores into ellipsoids, resulting in a unidirectionally shrunken, but still well-defined and fully accessible bcc mesopore architecture. The influence of mesoporosity and crystallinity on electrochemical/electrochromic characteristics was addressed by monitoring electrochemical features and the absorption changes during Li insertion/extraction (repetitive potentiostatic cycling). Both the amorphous and crystalline mesoporous films possess electrochromic response times on the order of only seconds, which are attributable to the facilitated insertion of guest ions due to shortening of the diffusion path lengths. Also, the insertion/extraction reversibility of crystalline WO3 layers with 3D mesoporosity is improved compared to amorphous ones and reaches values close to 100%.

Robust Sandwich‐Structured Nanofluidic Diodes Modulating Ionic Transport for an Enhanced Electrochromic Performance

“…Conversely, the colored WO 3 was bleached, while NiO was the opposite with the extraction of Li + ions driven by the oxidation potential, which caused the color of the membrane to turn tawny. It is worth mentioning that the annealing temperature was reduced to 300 °C because the compact films prepared at a higher temperature were too dense for ion insertion during the reduction process 22. In this case, the sandwich‐structured nanofluidic diodes exhibit an ion rectification behavior with a lower ratio of 8.2 compared with those annealed at 500 °C (Figure S17, Supporting Information).…”

Low temperature crystallisation of mesoporous TiO2

“…Mesoporous, nanocrystalline TiO 2 is an interesting and useful material for a wide range of applications, such as dyesensitised solar cells 1,2 , photocatalytic reactors 3,4 , electrochemical capacitors 5 , chemical and biochemical sensors 6,7 , and electrochromic devices 8 . These electrochemical devices require an electron-conducting network with pores on the 10-nm length scale.…”

Electrochromic properties of self-organized multifunctional V2O5–polymer hybrid films

“…Aer equilibration of the system achieved aer few switching cycles, the composite structures showed distinct transitions between intercalated (reduced/bleached) state and deintercalated (oxidized/coloured) state with a change in transmittance of $25% at 450 nm and a good long-term cycle stability with a decrease of less than $20% over more than hundred switching cycles ( Fig. 2 27 respectively. Even aer performing a hundred switching cycles and storing the electrochromic devices in the oxidized i.e.…”