Showing papers on "Electrochromism published in 1989"

Functionalized polypyrroles. New molecular materials for electrocatalysis and related applications

Abstract: The concept of altering the chemical structure of an electrode surface with a view to controlling the course of an electrochemical reaction was pioneered some 15 years ago by Lane and Hubbard. This promising new areas of electrochemistry rapidly attracted interest, the major objective being to tailor spectifically the electrode material in such a way as to promote the desired electrochemical reaction. The possibility of making electrodes with specific chemical, electrochemical, or optical surface properties gave rise to numerous possible applications of these modified electrodes in the fields of electro- and photocatalysis, electrosynthesis, electroanalysis, molecular devices, and electrochromism. Among the numerous chemical functions that could undergo electrochemical polymerization, the pyrrole group is exceptionally convenient for carrying out the coating of electrode surfaces by nonpassifying polymer films containing catalytic and/or redox active centers. Furthermore, polypyrrolic films are characterized by a long-term chemical stability, which allows their productive use in various applications. An account of this topic, mainly devoted to electrocatalytic applications, will be given here. A few typical extra examples, including bio- and electroanalysis, microelectronics, and electroreleasing devices, are also presented to emphasize the versatility of this type of polymeric coating.

Anodically Electrodeposited Iridium Oxide Films (AEIROF) from Alkaline Solutions for Electrochromic Display Devices

Abstract: Anodically electrodeposited iridium oxide films from alkaline solutions were investigated for application to electrochromic devices Micro-crystalline (diameter: 15A) films obtained by the electrolysis of aqueous alkaline solutions containing iridium chloride, oxalic acid and potassium carbonate showed good electrochromic reaction reversibility The coloration efficiency of the films was about one third that of typical evaporated tungsten oxide films, and the response rate measured by the amount of injected charge was about double The cycle lives of the cells, composed of electrodeposited films, 1M H3PO4-NaOH (pH=3~5), and an activated carbon cloth, were more than 8 × 106 with a 06 V, 1 Hz continuous square wave

Optical properties of electrochromic vanadium pentoxide

Abstract: Electrochemical and spectroscopic measurements were used to characterize the electrochromic behavior of sputtered V2O5 films. In response to lithium intercalation, the fundamental optical absorption edge of V2O5 shifts to high energies by 0.20–0.31 eV as the lithium concentration increases from Li0.0V2O5 to Li0.86V2O5. There is a corresponding increase in the near‐infrared absorption that exhibits Beer’s law behavior at low lithium concentrations. The shift in absorption edge results in a large decrease in absorbance in the 350–450 nm wavelength range. This effect is most prevalent in thin films which exhibit a yellow to colorless optical modulation on lithium intercalation. The cathodic coloration in the near infrared is relatively weak with a maximum coloration efficiency of 35 cm2/C.

Electrochromic properties of conducting polyanilines

Abstract: A study has been made of the electrochromic behaviour of polyaniline films of potential use in passive display devices, and a preliminary examination of the properties of substituted polyanilines has also been carried out. Films of 'emeraldine-type' conducting polyanilines have been grown electrochemically from aqueous solutions onto glass substrates coated with gold or indium tin oxide. The authors have studied the electrochemistry of their redox reactions in acidic media to examine the kinetics and reversibility. Cyclic voltammetry was used to determine the electrode potentials for growth and redox switching and to obtain information on the electrode kinetics. The effect of electrode potential on the optical absorption spectra was observed, and was found to be consistent with polaron and bipolaron formation. The electrochromic colour contrast and switching times were measured as a function of pH; the requirements were somewhat conflicting, but a satisfactory compromise could be obtained around pH=0. By switching the electrodes over a constant potential step but from a variety of starting potentials, the influence on switching times of the initial oxidation state, and hence of the film conductivity, was investigated. Under suitable circumstances electronic conductivity, ionic transport or interfacial charge-transfer can limit the switching speed, but response times (for 50% transmission change) as short as 15 ms have been obtained without full optimisation. Of the numerous substituted polyanilines tried, only simple alkyl and alkoxy derivatives formed good polymeric films, and only the 2-ethoxy and 2-methoxy polymers gave good electrochromic behaviour. Switching times for these two were very fast, being less than 2.5 ms for both oxidising and reducing potential changes.

Electrochromic Li(x)WO(3)/poymer laminate/Li(y)V(2)O(5) device: toward an all-solid-state smart window.

Abstract: We introduce a laminate two-layer approach to electrochromic smart windows. It incorporates two glass panes, each having a two-layer coating, laminated by a transparent adhesive solid polymer electrolyte. Each coating has a transparent conducting base layer (In2O3:Sn) and a top layer of an ion-insertion compound (based on WO3 or V2O5). The layers were made by evaporation or sputtering. Cyclic voltammetry in liquid electrolytes and spectrophotometry were used to characterize the layers. A novel electrolyte was developed: it comprised a methyl methacrylate network incorporating poly(propylene glycol) complexed with lithium perchlorate. Initial optical data are reported for laminated devices having an active electrochromic LixWO3 layer and a passive LiyV2O5 counter electrode.

Poly ( N ‐ Benzylaniline ) / ( Poly ( AMPS ) / WO 3 Solid‐State Electrochromic Cell

Abstract: We report here a new solid-state electrochromic cell PPW: SnO 2 /Poly(BAn)/Poly(AMPS)/WO 3 /SnO 2 where poly(N-benzylaniline), Poly(BAn), and WO 3 are the electrochromic thin films prepared by electrodeposition and poly(2-acrylamido-2-methylpropanesulfonic acid), Poly(AMPS), the proton conducting polymer electrolyte film

Electrochemistry of some β‐Substituted Polythiophenes: Anodic Oxidation, Electrochromism, and Electrochemical Deactivation

Abstract: The anodic electrochemistry of the soluble poly(3-ethylmercaptothiophene) (PEMT) and poly[3,4-bis(ethylmercapto)thiophene] (PBEMT), is compared with the behavior of polythiophene (PT), poly(3-methylthiophene) (PMT), and poly(3-hexylthiophene) (PHT). In all five cases, the first anodic oxidation was reversible and was accompanied by reversible electrochromic behavior. When the polymers were driven to more positive potentials, there was immediate loss of electroactivity and concomitant color change to black. An electrochemical cross-linking/chain extension technique is discussed for PEMT as a means of growing smooth polymer films on electrode substrates starting from soluble oligomers in solution

Electrochromic Molybdenum Oxide Thin Films Prepared by Electrodeposition

Abstract: We report the first preparation of molybdenum oxide thin films by electrodeposition and the effect of the heat treatment on their electrochromic properties

Permanently doped polyaniline and method thereof

Abstract: The present invention relates to an electrically conducting polymer, the water-insoluble polymer having essentially permanent self-doping properties, and the polynmer comprises: (a) electrically polymerized polyaniline in covalent combination with (b) an organic dopant having at least one sulfonic acid functional group. The electrically conducting polymer-dopant is preferred wherein the organic dopant is selected from benzenesulfonic acid, toluenesulfonic acid, benzenesulfonyl chloride, dodecylbenzenesulfonic acid, poly(vinylsulfonic) acid, trifluoromethanesulfonic acid, 1-butanesulfonic acid, modified NAFION, 2,3,5-trichlorobenzenesulfonic acid, vinylphenylsulfonic acid, or the alkali metal salts thereof. In another aspect, the present invention discloses a method to produce a water-insoluble polyaniline in which an aromatic organic dopant is covalently bonded to the polyaniline, which method comprises (a) electropolymerizing aniline in an aqueous solvent which contains the organic dopant. These permanently doped polyanilines are useful as films for electric battery electrodes, and for electrochromic applications.

An Electrochromic Window Based on Li x WO 3 / ( PEO ) 8LiClO4 / NiO

Abstract: Electrochromic materials are characterized by reversible but persistent changes of the optical properties when subjected to suitable electrochemical reactions. Electrochromism can be utilized in windows, most conveniently by exploiting all-solid-state multilayer coating backed by glass. The multilayer coating should comprise the following sequence of layers: a transparent and electrically conducting base layer, an electrochromic layer, and electrolyte, a conterelectrode, and a transparent conducting top layer. For window applications, the electrolyte should be transparent, and the conterelectrode must be either optically passive (colorless irrespective of its ionic content) or electrochromic in a sense that is complementary to the electrochromism of the electrochromic layer. The latter condition implies that if the electrochromic layer is cathodic (anodic), the counterelectrode must be anodic (cathodic). This paper reports preliminary data taken on samples with electrochromic layers based on tungsten oxide, WO{sub 3}, and nickel oxide, NiO, and an intermediate solid electrolyte of poly(ethylene oxide) doped with lithium perchlorate, (PEO){sub 8}LiClO{sub 4}, where 8 signifies the number of oxygen heteroatoms per lithium ion.

Electrochemical assembly of metallopolymeric films via reduction of coordinated 5-chlorophenanthroline

Abstract: Electrochemical reduction of iron, osmium, and ruthenium complexes containing the ligand 5-chlorophenanthroline leads to the controlled growth of metallopolymers as electrode coatings. The coatings are electroactive and display a reversible electrochromic effect upon metal oxidation. Auger electron spectroscopy studies show that the polymerization mechanism involves carbon-chlorine bond cleavage and the generation of exchangeable chloride ions. The proposed linkage mechanisms involve direct carbon-carbon coupling of phenanthroline ligands. The possible utility of these new polymers in redox conductivity studies and in microstructure fabrication is noted

Sol-gel synthesis of electrochromic films☆

Abstract: The sol-gel process offers new approaches to the synthesis of electrochromic materials. Oxide networks are formed upon hydrolysis-condensation of alkoxide precursors. Layers can be easily deposited by dip coating. V 2 O 5 gels give rise to anisotropic electrochromic layers that turn from yellow to green. A three-colour device (red-yellow-green) can even be obtained with thick V 2 O 5 layers. TiO 2 gels give amorphous coatings that turn from transparent to grey. However, it has to be pointed out that the colouration of the electrochromic layer can be changed by using chemical additives such as acetic acid. The coloured state thus becomes blue instead of grey.

Thin film ion conducting coating

Abstract: Durable thin film ion conducting coatings are formed on a transparent glass substrate by the controlled deposition of the mixed oxides of lithium:tantalum or lithium:niobium. The coatings provide durable ion transport sources for thin film solid state storage batteries and electrochromic energy conservation devices.

Electrochromism of Polyaniline: An In Situ FTIR Study

Abstract: Electrochromic thin films of polyaniline were prepared by electropolymerization of aniline from an acidic aqueous solution on platinum and conducting glass surfaces. An in situ FTIR spectroelectrochemical technique was used to investigate structural changes of the film during oxidation and reduction. Coloring (oxidation) and bleaching (reduction) of the film were shown to be associated with the deprotonation and protonation of the film. It was detected that the N‒H stretching band around 2970 cm−1 decreased as the film was gradually oxidized.

Electrochromic window with integrated bus bars

Abstract: An electrochromic window includes a first transparent substrate, an electroconductive film electrode, a transparent electrochromic film in contact with said electroconductive film, an ion-conductive layer in contact with said electrochromic film, a counter electrode in contact with said ion-conductive layer, and a second transparent substrate overlaying the counter electrode. A plurality of bus bars extend across the electroconductive film electrode to distribute electrical current throughout the film electrode and provide a more uniform current density between the film electrode and the counter electrode.

Polymeric solid electrolytes and production process thereof

Abstract: Polymeric solid electrolytes are formed by the present invention, namely, by incorporating a low molecular weight polyethylene glycol, a high molecular weight polyethylene oxide and an alkali metal or ammonium salt in a specific cinnamate ester compound, followed by a polymerization and crosslinking. The polymeric solid electrolytes have high ionic conductivity, high strength as a film, and good adhesion with electrodes. Therefore, they can be applied widely as ionics materials, e.g., for the total solidification of lithium batteries and plastic batteries and high capacity condensers and as electrolytes for electrochromic displays.

Solid state electrochromic light modulator

Abstract: An all solid-state variable transmission electrochromic device has a source of charge compensating ions. An inorganic oxide counterelectrode film which on reduction with the accompanying insertion of the charge compensating ions increases its transmission of light of predetermined wavelength is separated from a primary electrochromic film which on reduction with the accompanying insertion of the charge compensating ions decreases its transmission of light of predetermined wavelength by an insulating electrolyte film that transports the charge compensating ions. First and second electrodes are contiguous with the inorganic oxide counter electrode film and the primary electrochromic film, respectively, and separated by the three films.

Solid electrolytes for conducting polymer-based color switchable windows and electronic display services

Abstract: Electrochromic material, i.e. polyaniline, is polymerized in situ in a polymeric electrolyte to form an electrochromic/polyelectrolyte mixture. The mixture is coated as a film on electrochromic material. A film of electrolyte is placed in ion transfer relationship with the electrochromic/polyelectrolyte film. This electrochromic/polyaniline/polyelectrolyte film greatly increases the ion transfer between the electrochromic film and the electrolytic film by imposing a region of molecularly mixed electrochromic material and electrolyte.

Laminated and sealed electrochromic window

Abstract: An electrochromic transparency comprising an electrochromic film and a preformed, preconditioned ion-conductive polymer sheet laminated between a pair of electrode bearing cell members is disclosed wherein the optimum moisture content of the ion-conducting polymer sheet is maintained by means of a moisture vapor barrier surrounding the perimeter of the cell.

Ion-beam based deposition of coatings for electrochromic devices

Abstract: Thin film coatings for solid state storage batteries and electrochromic energy conservation devices are now formed on low temperature glass and plastic substrates by an ion-assisted RF deposition process. The attachment of such coated glass or plastic substrates to existing windows in situ allows ordinary plate glass windows in homes, office buildings and factories to be converted to "smart-windows" resulting in a substantial savings in heating and air conditioning costs.

Role of the water content on the electrochromic properties of WO3, nH2O thin films

Abstract: Tungsten oxide films can be deposited from colloidal solutions in order to make electrochromic devices. Depending on the experimental procedure, more or less hydated crystalline or amorphous oxides can be made. The electrochromic properties of these oxides depend strongly on the amount of water. Li+ diffusion into the oxide layer becomes much easier when their water content increases. This observation is interpreted in terms of water adsorption and dissociation at the surface of the oxide. Solvent and ion exchange occur spontaneously at the electrolyte-electrode interface, even in the absence of any applied voltage, therefore decreasing the interface discontinuity between the two phases.