In this study, vanadium sesquioxide (VO), dioxide (VO), and pentoxide (VO) were all synthesized from a single polyol route through the precipitation of an intermediate precursor: vanadium ethylene glycolate (VEG). Various annealing treatments of the VEG precursor, under controlled atmosphere and temperature, led to the successful synthesis of the three pure oxides, with sub-micrometer crystallite size. To the best of our knowledge, the synthesis of the three oxides VO, VO, and VO from a single polyol batch has never been reported in the literature. In a second part of the study, the potentialities brought about by the successful preparation of sub-micrometer VO, VO, and VO are illustrated by the characterization of the electrochromic properties of VO films, a discussion about the metal to insulator transition of VO on the basis of in situ measurements versus temperature of its electrical and optical properties, and the characterization of the magnetic transition of VO powder from SQUID measurements. For the latter compound, the influence of the crystallite size on the magnetic properties is discussed.

Devices displaying controllably tunable optical properties through an applied voltage are attractive for smart glass, mirrors, and displays. Electrochromic material development aims to decrease power consumption while increasing the variety of attainable colors, their brilliance, and their longevity. We report the first electrochromic device constructed from metal organic frameworks (MOFs). Two MOF films, HKUST-1 and ZnMOF-74, are assembled so that the oxidation of one corresponds to the reduction of the other, allowing the two sides of the device to simultaneously change color. These MOF films exhibit cycling stability unrivaled by other MOFs and a significant optical contrast in a lithium-based electrolyte. HKUST-1 reversibly changed from bright blue to light blue and ZnMOF-74 from yellow to brown. The electrochromic device associates the two MOF films via a PMMA-lithium based electrolyte membrane. The color-switching of these MOFs does not arise from an organic-linker redox reaction, signaling unexplored possibilities for electrochromic MOF-based materials.

We demonstrate the benefit of home-made nanopowder precursors on the electrochromism of V 2 O 5 films deposited by the "Doctor Blade" method. Using the polyol process, nano-structured V 2 O 5 powder were synthesized. Orthorhombic V 2 O 5 thin films deposited from as-synthesized powder exhibit good cycling stability associated with significant reflectance modulation in both lithium and sodium based electrolytes. The orange to green reversible color change appears well suitable for display application. To conclude, the electrochromic performances of complete devices using WO 3 as complementary electrode and 0.3 M Lithium Bis(Trifluoromethanesulfonyl)Imide LiTFSI in BMITFSI plastified with polymethylmetacrylate (PMMA) membrane electrolyte are reported.

Our e-connected society is eager to develop devices with tunable colors. Electrochromic materials, able to modify their optical properties under an applied voltage, offer a smart solution. In the present study, we have successfully synthesized two vanadium oxide powders from a polyol mediated synthesis and powder suspensions were coated on glass/ITO substrates by doctor blading. The electrochemical and optical properties of the VxOy films are investigated by cyclic voltammetry (CV) coupled with insitu UV-Visible spectroscopy. Both V2O5 and V2O3 films exhibit reasonably good cycling stability, significant reflectance modulation, high optical contrast and good memory effects revealing the unknown EC properties of V2O3. The similar green ⇄ blue ⇄ orange reversible color changes for both vanadium oxides appears suitable for display application. Then, the evolution of the vanadium cation oxidation states and of the structure of V2O5 and V2O3 upon cycling are analyzed by ex-situ XPS and ex-situ XRD (at grazing incident angle). This work highlights a robust and novel scenario upon cycling, nearly the same whatever the raw film composition that shows, for each cycle, the crystallization of V2O5 upon oxidation, followed by amorphization upon reduction. I.

Transition metal oxides (TMOs) have attracted considerable attention due to their variety of chromogenic properties. Among them, vanadium pentoxide (V2O5) has gained significant interest in respect of multichromism associated with orange, green and blue colors. Herein, we report a simple and easy method for the fabrication of Mo doped V2O5 thick films, leading to improved cyclability. Molybdenum doped vanadium pentoxide powders were synthesized from one single polyol route through the precipitation of an intermediate precursor: molybdenum doped vanadium ethyleneglycolate (Mo doped VEG). The as-synthesized Mo-doped V2O5 exhibits improved electrochromic performance in terms of capacity, cycling stability, and color contrast compared to single-component V2O5 in lithium as well as sodium based electrolyte. The improvement in EC performances lies in films of higher porosity as well as higher diffusion coefficients. To conclude, an electrochromic device combining Mo-V2O5 to WO3.2H2O, via a PMMA-lithium based electrolyte membrane exhibit simultaneously reversible color change from yellow to green for Mo-V2O5 and from blue to yellow white for WO3.2H2O with a cycling stability up to 10 000 cycles.

Poly(3,4-ethylenedi-oxythiophene) (PEDOT) derivatives conducting polymers are known for their great electrochromic (EC) properties offering a reversible blue switch under an applied voltage. Characterizations of symmetrical EC devices, built on combinations of PEDOT thin films, deposited with a bar coater from commercial inks, and separated by a lithium-based ionic membrane, show highest performance for 800 nm thickness. Tuning of the color is further achieved by mixing the PEDOT film with oxides. Taking, in particular, the example of optically inactive iron oxide Fe2O3, a dark blue to reddish switch, of which intensity depends on the oxide content, is reported. Careful evaluation of the chromaticity parameters L*, a*, and b*, with oxidizing/reducing potentials, evidences a possible monitoring of the bluish tint.

Smart multifunctional V2O5 is an appealing oxide for energy–saving and energy–storage applications. This review article comprehensively analyzes the most recent advances and applications. The unique electronic structure of V2O5 with...

No abstract