Showing papers on "Electrochromism published in 1992"

Gel Electrolyte for Solid‐State Electrochromic Cell

Abstract: The preparation, the electrical and rheological properties as well as the electrochemical behavior of gel electrolytes made of (PC) electrolyte mixed with poly(methylmethacrylate) polymer (PMMA) as a stiffener are described. The addition of PMMA in various proportions to (M)‐PC electrolyte considerably increases the viscosity to reach for large amounts of PMMA, a solid rubber‐like material. On the other hand the conductivities at room temperature of these gels decrease very slightly and remain very close to the conductivity of the liquid electrolyte. Moreover, the electrochemical study of these materials shows a stability domain on Pt electrode between −3.55 V and +1 V (vs.Ag/Ag+). They behave like a liquid electrolyte. Differential scanning calorimetric data establish the thermal stability of these gels between −110 and +240°C after heat‐treatment and between −90 and +160°C before heat‐treatment. These results indicate that this type of electrolyte which is transparent in thin films is very promising for the realization of solid‐state electrochromic windows.

A Study of Tungsten Trioxide and Polyaniline Composite Films I . Electrochemical and Electrochromic Behavior

Abstract: This paper discusses tungstic oxide/polyaniline composite films prepared by a double-pulse electrodeposition technique, and their properties which were investigated by in situ optical and electrochemical techniques. Such composite films are more conducting than pure WO{sub 3} films. The films have an electrochromic window between the anodic coloration of polyaniline and the cathodic coloration of tungsten trioxide. The films should find useful applications as multicolor display devices.

Electrochemical studies of the factors influencing the cycle stability of Prussian Blue films

Abstract: Some of the factors leading to long term cycle stability for Prussian Blue (PB) films are determined. The pH of the conversion electrolyte was found to be the overwhelming factor in film stability; cycle lifetimes in excess of 100 000 were easily achieved in solutions of pH 2–3. Concurrent with the increase in stability at lower pH was a considerable increase in switching kinetics. Surprisingly, the films grown from chloride-containing solutions were found to be slightly more stable, in terms of cycle life, compared to those grown from chloride-free solutions. In addition, we found that there occurs at least some conversion of PB form during the first cycle, and thus, form conversion kinetics cannot be evoked as a mechanism for film stability. Unfortunately, the films grown electrochemically on ITO glass exhibited a white haze which we attribute to light scattering caused by grain size. Unless it can be eliminated, this haze effect will be a serious drawback in the eventual use of PB in an electrochromic filter. Finally, the films were stable in mixed solvents that provide an expanded temperature range, and preconditioned films were stable to drying and immersion in boiling water.

Electrochromic-photovoltaic film for light-sensitive control of optical transmittance

Abstract: A variable transmittance optical component includes an electrochromic material and a photovoltaic device-type thin film solar cell deposited in a tandem type, monolithic single coating over the component. A bleed resistor of a predetermined value is connected in series across the electrochromic material and photovoltaic device controlling the activation and deactivation of the electrochromic material. The electrical conductivity between the electrochromic material and the photovoltaic device is enhanced by interposing a transparent electrically conductive layer.

Electro-optic device

Abstract: Electro optic devices incorporating an improved configuration of elements which dramatically reduces light scattering and haziness with relatively inexpensive coated glass The devices are liquid or gel containing electro optic devices, such as an electrochromic automatic rearview mirror for automotive vehicles, which has for at least one of its walls a sheet of glass coated with a transparent conductive coating The combination of the coated glass, which has a tendency to have an optically rough surface, and the liquid or gel electro optic material reduces the scattering of any incident light by wetting out the rough optical surface of the coated glass, thereby improving the optical quality The coated glass scatters between 02 and 40% of visible white light prior to assembly into the device

Method for depositing electrochromic layers

Abstract: Electrochromic coating solutions are prepared by reacting a transition metal with a mixture of hydrogen peroxide and an organic acid. The resulting transition metal-peroxy acid product is esterified by reacting with lower carbon alcohols to produce a peroxyester-transition metal derivative. This derivative in solution in lower carbon alcohols provides a working solution into which a substrate having a conductive surface is preferably dipped and removed at a rate sufficient to give a coating of a desired thickness over the conductive surface. Spray or spin coating can be used to apply the coating to the conductive surface of the substrate. The coating is then dried and is externally fired in an oven to complete the necessary reactions to yield an electrochromic oxide coating having exceptional electrochromic properties.

Image projection display screen employing polymer dispersed liquid crystal layer and electrochromic layer

Abstract: A diffusing display screen resulting from the combination of a cell comprising a polymer dispersed liquid crystal material which can be made diffusing, and of a cell comprising an electrochromic material which can be made absorbing and reflecting. Outside the operating mode, the display screen according to the invention has the advantage of being transparent, and thus capable of being fixed onto any surface (window, wall, etc.).

An optoelectrochemical thin-film chlorine sensor employing evanescent fields on planar optical waveguides

Abstract: A new type of optoelectrochemical sensor based on an electrochromic thin-film sensing layer placed on top of a planar waveguide has been developed. The oxidation state of the sensing film is quantitatively measured by the evanescent field of the light transmitted through the waveguide. The functioning of the device has been ascertained which dissolved chlorine, employing an electrochemically resettable film of lutetium biphthalocyanine. Detection of film oxidation has been carried out at 950 nm. This technique appears promising for the detection of residual chlorine, since only changes due to the sensing reaction are monitored. Although the device has not been optimized, a potential sensitivity below 1 ppm has been demonstrated. The integration of modem optical technology and electrochemical techniques for sensing applications appears to be a powerful new approach.

UV-stabilized compositions and methods

Abstract: The present invention concerns compositions, which comprise a solvent, which is suitable for a medium of variable transmittance in a solution-phase electrochromic device, and a UV-stabilizer, which is an ester of 2-cyano-3,3-diphenyl acrylic acid. Among embodiments of the invention are solutions used as media of variable transmittance in electrochromic devices, especially single-compartment, self-erasing, solution-phase electrochromic devices. The UV-stabilizer provides to the compositions of the invention stability against degradation from exposure to ultraviolet radiation, including that from the sun. Among applications of electrochromic devices comprising solutions according to the invention are use as variable transmittance components in variable reflectance, outside, rearview mirrors for automobiles.

Tinted solution-phase electrochromic devices

Abstract: The invention provides improved solution-phase electrochromic devices, wherein the solution of reversibly variable transmittance is tinted with a tint-providing compound, and solutions of reversibly variable transmittance for use in the improved devices of the invention. An electrochromic device of the invention can be used, for example, as the component of reversibly variable transmittance in a variable-reflectance motor vehicle mirror. Among such mirrors provided by the invention are blue-tinted mirrors.

Electrochromic properties of vanadium pentoxide thin films prepared by new wet process

Abstract: Electrochromic properties of the V2O5 thin films prepared from a spinnable organic vanadium solution were investigated. The films heat‐treated at 400 °C showed clear two‐step electrochromism, deep blue⇄green⇄yellow, with its response time for obtaining ΔOD=0.5 being ∼2 s. The yellow and green colors showed good memory effects for more than 20 h, while the blue one was considerably degraded within 10 h.

Prolonged lifetime of electrochromism of amorphous WO3–TiO2 thin films

Abstract: The lifetime of the electrochromism of the WO 3 -TiO 2 films prepared by vacuum evaporation is found to exceed that of WO 3 films by a factor of five. X-ray diffraction has revealed that the crystal structure of WO 3 -TiO 2 films stays amorphous, while crystalline compounds are formed in amorphous WO 3 films after colouring and bleaching. WO 3 -TiO 3 films stay amorphous after they are annealed at 400 o C, although WO 3 films crystallize

Smart zeolites: New forms of tungsten and molybdenum oxides

Abstract: In this Account, the authors describe their recent research efforts involving the use of volatile hexacarbonylmolybdenum and -tungstem compounds, as precursors in the synthesis of highly organized assemblies of molecular dimension molybdenum and tungsten oxides, encapsulated within the diamond network of 13-[Angstrom] supercages found in zeolite Y. These assemblies are extremely uniform in terms of their nuclearity and structure, and their exclusive internal confinement inside of and lack of significant perturbation of the zeolite Y host. In these materials, the bulk form of the metal oxide has essentially been reconstituted within the nanoscale void spaces of a crystalline aluminosilicate framework host. The electronic and structural properties of these molecular metal oxide arrays can be easily manipulated as a result of their facile redox interconvertibility, and the further capability of fine tuning their electronic enviornment by choosing which charge-balancing cation is present in the supercage. Bulk forms of WO[sub 3] and MoO[sub 3], which possess octahedral building blocks arranged into open framework, layer, and tunnel structures, are probably most famous for their ability to reversibly accept metal cations and protons into their internal void spaces and electron-charge-transfer equivalents into their conduction bands. This fascinating property enables them to function as intelligentmore » materials in, for example, electrochromic windows, mirrors and displays, rechargeable solid-state batteries, pH-microelectrochemical transistors, and chemical sensors. In addition, their narrow-band-gap semiconductor properties allow them to be usefully exploited in liquid junction solar and electrochemical cells.23 refs., 5 figs., 1 tab.« less

Electrochromism of vanadium‐titanium oxide thin films prepared by spin‐coating method

Abstract: Electrochromic properties of V2O5‐TiO2 thin films prepared by a spin‐coating method were strongly dependent on the film compositions and heat‐treatment temperatures. It was found that the nearly amorphous film of V2O5‐TiO2 (3:7 in molar ratio) heat‐treated at 400 °C showed coloration to reddish brown when polarized at −0.8 V vs SCE. This new coloration was concluded to be ascribable to amorphous vanadium oxide.

Study of electrodeposited tungsten trioxide thin films

Abstract: WO3 films have been electrodeposited in a solution containing dissolved tungsten and alcohol. The deposition conditions and the deposition efficiency on various substrates were studied. The properties of the electrodeposited WO3 film were characterised by electrochemical, surface analytical and in situ optical techniques. The results indicated that the electrodeposited WO3 films have similar electrochromic behaviour to that of anodically grown WO3 films. A Nernst type response for H+ concentration has been demonstrated on reduced films, with a slope of 64 mV (pH)–1. The electrodeposited films have selective permeability to different ions and molecules. Since the zero-charge potential of the electrodeposited film is much more anodic, anions such as Fe(CN)63–/Fe(CN)64– cannot enter the n-type film at potentials more negative than its zero-charge potential. However, some cations can diffuse in and out of the electrodeposited WO3 film reversibly.

Characterization of electrochromic nickel oxide thin films prepared by anodic deposition

Abstract: Nickel oxide (NiOx) thin films have been prepared on transparent conducting indium tin oxide (ITO) substrates by anodic deposition from a nickel ammine complex solution. Electrochromic (EC) behaviour of these films was observed in a borate buffer solution at pH 10 in the potential range 0–1 V vs. Ag/AgCl; an as-prepared film (PF) was cathodically reduced to a colourless form (RF) and oxidized to a brown form (OF) by anodic polarization. Characterization of these films by low-angle incident X-ray diffraction and X-ray photoelectron spectroscopy with argon-ion (Ar+) etching revealed that the EC properties are based on the electrolytic transformation of the NiOx structure between β-NiOOH and β-Ni(OH)2, i.e. involving the redox reaction Ni3++ e ⇄ Ni2+.