Showing papers on "Electrochromism published in 1979"

The Electrochromic Process at WO3 Electrodes Prepared by Vacuum Evaporation and Anodic Oxidation of W

Abstract: The kinetics of the electrochromic process and the stability with different WO3 electrodes (evaporated film, electrodes obtained by anodic oxidation of W, polycrystalline, and single crystal) were studied. Cyclic voltammetry and chronoamperometr y, together with optical absorption measurements in the electrochromic region were carried out. Impedance measurements at different frequencies of the WO3-H2SO4 (aq) interface were also made to compare the evaporated film and anodic oxide electrodes. These measurements showed that the electrochromic reaction at the WO3 anodic film was much faster than that at the evaporated film electrode (by about two to three orders of magnitude). This difference in the reaction rates reflects the difference in the rate of diffusion of H + in the films. Infrared spectroscopic measurements of the films were carried out to obtain information about the water content of the films. The differences in the kinetic behavior of the electrochromic process at the two electrodes were attributed to differences in porosity and water content of these two films. The stability of the WO3 film toward dissolution in aqueous solution was also shown to depend on the quantity of water in the film. In addition electrochemical behavior in the electrochromic region was studied in several other systems, including systems which contain H~SO~ as the electrolyte but with nonaqueous solvents and systems which contain Li +, replacing H +, in nonaqueous solvents. The solvent and the cation both affect the kinetics of the electrochromic process and the stability of the amorphous films. The electrochromic process at single crystal and polycrystalline WO3 was also studied and compared to the behavior of the amorphous film electrodes.

Electrochromism in Anodic Iridium Oxide Films II . pH Effects on Corrosion Stability and the Mechanism of Coloration and Bleaching

Abstract: The oxidation state of iridium ions in an oxide film, grown electrochemically on an Ir metal reflector electrode, can be rapidly and reversibly modulated according to the electrochromic redox reactionBy suitable choice of electrolyte composition and potential limits, the coloration and bleaching processes can be effected without causing oxide film growth or dissolution, or electrolyte decomposition. Color‐bleach (c‐b) cycles exhibit reflectance contrast changes, , and charging times, τ, suitable for electrooptic display devices, e.g., for a film 320 nm thick, at and . Long term corrosion stability is obtainable in mildly acidic sulfate electrolytes, e.g., at pH 3.5. Sulfate electrolytes are also apparently unique in preventing degradation of c‐b response times owing to changes in film structure. East write‐erase times are made possible by the highly porous and hydrated nature of the oxide film and the ready availability of the protons required for bleaching from an 'internal' source—free molecules in the electrolyte contained within the film pores and/or bound or OH groups on the oxide surface. The kinetics and mechanism of the electrochromic reaction in anodic iridium oxide films are discussed with particular reference to the requirement for preserving electroneutrality within the bulk oxide. Recent claims that this redox reaction can occur without exchange of protons with the electrolyte are shown not to be substantiated. Attractive features of the electrochromic iridium oxide system for display devices include: (i) broad spectral absorption; (ii) good contrast ratio; (iii) fast response; (iv) good corrosion stability; (v) good open‐circuit memory in the presence of water and dissolved ; (vi) suitable threshold and switching voltage levels; and (vii) the ability to grow and reform the oxide layer in situ in the electrooptic display cell. The charge (~20 mC cm−2) and energy (~30 mJ cm−2) required for coloration and bleaching are similar to those required for other electrochromic oxide systems, e.g., the tungsten bronzes.

Electrocatalytic oxygen evolution on reactively sputtered electrochromic iridium oxide films

Abstract: Oxygen evolution reactions1 are critical to the development of efficient energy conversion and energy storage devices For example, power losses at the oxygen electrodes of commercial water electrolysers2 and H2˙−O2 fuel cells limit their efficiencies to values well below those expected theoretically The power loss of these devices is ≳15% even at low current densities, and much higher in practical operating conditions We report here the preparation and the oxygen evolution reaction (OER) electrocatalytic properties of iridium oxide films deposited by reactively sputtering iridium in a humidified oxygen discharge We find that these sputtered iridium oxide films (SIROFs) have catalytic properties far superior to the best known catalysts for oxygen evolution in acidic aqueous electrolytes at room temperature

An Explanation of the Electrochromism of Lutetium Diphthalocyanine

Abstract: Lutetium diphthalocyanine can be electrolyzed reversibly in dimethylformamide to give four different colored solutions: violet, blue, green, and yellow‐red. Two of these solutions, the violet and the green, also exhibit electron paramagnetic resonance (EPR) signals indicative of organic‐free radicals. The blue and the yellow‐red solutions are EPR silent. The oxidation state of the phthalocyanine nucleus is responsible for the electrochromism of this rare‐earth complex. The EPR signal of the violet form, which is produced by electrolytic reduction and which is probably the anion radical of the complex, has a . The signal of the green form, which is the initially prepared material and which is probably a salt containing the cation radical of the complex, has a . The optical absorption spectra and extinction coefficients of three of the forms are also reported.

Electrochromic iridium oxide films prepared by reactive sputtering

Abstract: We report the preparation and electrochromic properties of iridium oxide films deposited by reactively sputtering iridium in a humidified oxygen discharge. These sputtered iridium oxide films (SIROFs) have the fast coloring and bleaching kinetics and excellent stability previously observed for anodically grown iridium oxide films (AIROFs). SIROFs deposited on SnO2‐coated glass can be modulated from clear to blue‐gray with properties similar to those of AIROFs. In addition, SIROFs deposited on metal substrates exhibit a variety of colors which can be electrically altered. This adds a new dimension to the range of potential applications for iridium oxide displays.

Semiconductor Electrodes XXII . Electrochromism and Photoelectrochemistry at Layers Prepared by Thermal and Anodic Oxidation of W

Abstract: Electrochromism was studied with layers prepared by thermal oxidation of W, and compared to the electrochromic behavior of other electrodes (anodic, amorphous, and annealed films) Although the layers obtained by thermal oxidation of W are crystalline, the electrochromic performance with this electrode is comparable to that of the evaporated amorphous electrode The photoelectrochemical behavior of these electrodes, and in particular the effect of a pretreatment of repeated color‐bleaching cycles, was also studied Repeated color‐bleaching cycles resulted in a significant improvement in the photoelectrolytic behavior of the layers The photocurrent increased and the spectral distribution of the photocurrent shifted to longer wavelengths The repeated color‐bleaching cycles also cause a great improvement in the electrochromic behavior of the electrode as compared to that of the initially prepared electrode

Electrochromic display device

Abstract: An electrochromic display device has a polymer film on the display electrode. In the writing step the polymer film on the display electrode is oxidized to a colored, non-transparent form. In the erasing step the polymer film is reduced to a neutral transparent form. A film of polyaniline is used in a preferred embodiment. A film of polypyrrole is used in another embodiment.

Polymer effect in electrochromic behavior of oligomeric viologens

Abstract: A series of oligomeric viologens were synthesized in order to investigate the polymer effect in electrochromic behavior of viologen compounds. These materials have a lower first-step reduction potential and a higher second-step reduction potential compared with monomeric viologens. As a result, they have wider potential separation, where stable viologene radical salts are produced. Spectroscopic analysis suggests that stable monomeric viologen radical salts do not exist in water, but there is some intramolecular interaction between viologen radicals of the oligomers. This intramolecular interaction is responsible for the reduction behavior and the stability of radical films of oligomeric viologens.

Electrochromic display device

Abstract: PURPOSE:To save power consumption and enable identification of display at all times even in a dark place by so disposing a luminous film so as to radiate electrochromic layer thereby forming the electrochromic display device.

Solid state electrochromic display

Abstract: This invention is directed to a multicolored display which is based upon the rare-earth dipthalocyanines, and having a protonconductive, solid electrolyte which is selected for the electrochemical compatibility thereof with the electrochromic material in the display. Typically, the solid electrolyte consists of hydrogen uranyl phosphate or a related heteropoly acid.

Electrochromism in nickel‐doped strontium titanate

Abstract: Electrochromism in SrTiO3 : Ni at 200–300°C has been investigated by electrical and optical measurements. (NiTiVO) ′ and Ni′Ti constitute the color centers on the cathode and anode sides, respectively. Oxygen vacancy drift determines the kinetics during the early state of coloration and during the entire process of bleaching. An activation energy of 0.95 eV for oxygen vacancy motion has been obtained from bleaching experiments.

Solid‐state electrochromic device consisting of amorphous WO3 and Cr2O3

Abstract: The electrochromic (EC) characteristics were investigated on a solid‐state EC device In2O3/a‐WO3//Cr2O3/Au which was prepared by vacuum deposition. Besides the color change caused by passage of current in the WO3 layer, the color of the Cr2O3 layer was also changed as a result of electrochemical reaction at the interface. In the open‐circuit condition after the coloration, rapid spontaneous discoloration was found due to bimolecular recombination of the colored species in both layers at the interface. The existence of adsorbed water molecules in the respective layers is essential for the solid‐state ECD. The ECD in this study was scarcely affected by the ambient condition and was able to operate in the high vacuum (e.g., 10—6 Torr) since the Cr2O3 layer adsorbed water tightly. Positive polarization of the Cr2O3 layer in an electrolyte solution (Na2SO4 aqueous solution) caused change in the color as a result of electrochemical reaction, whereas the coloration of a‐WO3 was taken place by negative polarization of the a‐WO3. We have confirmed that this ECD could be operated without any conspicuous deterioration after the reversible switching cycles more than 5×106 times.

Electrochromic effects in solid phosphotungstic acid and phosphomolybdic acid

Abstract: The electrochromic performance of all solid‐state cells employing phosphotungstic acid and phosphomolybdic acid is reported. These cells employ SnO2 as the viewing electrode and graphite as the back electrode. Diffuse reflectivity changes of ∼50% are readily achieved in ∼10 msec. The cells, in the bleached state, can be made white to red, and become black in the colored state.

Electrochromic display with one porous separator

Abstract: A porous separator is provided with an electrochromic display for containing an electrolyte, whereby a display electrode is continuously, electrically rotated to a counter electrode through the electrolyte. A filter separator is further provided together with the porous separator for urging the porous separator toward the display electrode and itself toward the counter electrode because of the elastic characteristic thereof. The filter separator can also contain the electrolyte. The porous separator provides a white background for the display electrode. The remaining electrolyte, except for the electrolyte in both the porous and the filter separators, is eliminated from the electrochromic display to provide a cavity within the electrolyte for cancelling the cubic expansion of the electrolyte when temperature rises. This cubic expansion cancelling cavity may be formed by injecting a bubble into the electrolyte. The cavity is settled at a fixed position by the provision of an electrolyte-impregnated separator means without any interference with the display and counter electrodes.

Iridium oxide based electrochromic devices

Abstract: Electrochromic devices based on electrochromic iridium oxide electrodes are disclosed. These electrodes are iridium oxide entities produced by vacuum deposition techniques such as by sputtering from an iridium target in the presence of an oxygen atmosphere. All solid state electrochromic devices utilizing such electrodes are possible.

Discovery of a new reversible electrochromic effect

Abstract: A new electrochromic effect based on the electrochemical intercalation of graphite is described. This effect seems to have a promising potential for applications in display devices.

Efficiency and humidity dependence of WO3‐insulator electrochromic display structures

Abstract: Contrast ratio, optical density, efficiencies, coloration, and bleaching times of WO3‐insulator (LiF, MgF2) sandwich display structures have been measured and are compared to the characteristics of WO3‐liquid electrochromic cells. The efficiencies of the two are comparable, but it is harder to achieve sufficient contrast in the solid‐state structures. Measurements in a controlled‐humidity environment demonstrate clearly the crucial role of the presence of water vapor in the operation of these sandwich structures. Transport of protons through the insulator is indicated as the rate‐limiting mechanism.

Electrochromic material and electro-optical display using same

Abstract: Electrochromic material for an electro-optic display includes an oxide of at least one transition metal having a structure related to a hexagonal tungsten bronze structure whereby ions of an electro-active material readily diffuse through the lattice structure. In a display the electrochromic material is positioned between two electrodes with an electrolyte between and contacting the electrochromic material and one electrode which comprises the electro-active material.

Solid‐state electrochromic cell with anodic iridium oxide film electrodes

Abstract: A new solid‐state electrochromic cell has been fabricated using an anodic iridium oxide film (AIROF) display electrode. The cell has the symmetric sandwich structure AIROF‖Nafion‖AIROF, with the Nafion solid electrolyte opacified by an in situ precipitation technique. A symmetric square‐wave voltage of 1.5 V amplitude produces clearly perceivable color changes from pale to dark blue‐gray in ≈1 sec when viewed in diffuse reflection. Good open‐circuit optical memory is exhibited: (typical loss in attenuation of 8%/day).

Material and device properties of a solid state electrochromic display

Abstract: A solid state electrochromic display with the following configuration: transparent conductor/WO3/Na1+xZr2SixP3−xO12/ Na03WO3/conductor has been fabricated and studied The properties of the electrodes are shown to be dependant upon the preparation conditions Two problems, specifically due to the solid state nature of this device, are also discussed These are the incompatibility of the WO3 layer with the processes necessary to deposit a transparent electrode onto it, and the large resistance at the solid electrode/electrolyte interfaces

Electrochromic display device

Abstract: An electrochromic display device with an improved current efficiency as well as with an extensive memory capability is disclosed; the device comprises a vapor deposited layer of an electrochromic material and a contiguous layer comprising chromium (III) oxide and the oxide of a transition metal or silicon also formed by vapor deposition. These two layers are sandwiched between a pair of electrodes at least one of which is light-transmitting.

Electrochromic light regulator

Abstract: An electrochromic light regulator for adjusting or regulating the amount of light passing therethrough comprises first, second and third electrode units stacked one above the other in spaced manner. A space between each adjacent two of the first to third transparent electrode units contains an electrochromic material and an ion conducting and electrically insulating layer. The second transparent electrode unit which is positioned intermediately between the first and third transparent electrode units serves as a counter electrode common to the first and third transparent electrode means.

Method for forming electrochromic film

Abstract: An amorphous electrochromic film prepared by vacuum evaporation under relatively high pressure of 2×10 -4 -2×10 -3 torr. The evaporated film is porous with packing density less than 0.65 and exhibits excellent reversibility after heat treatment at 250° C.-350° C. whereby it is optimum for an electrochromic device sealed with a sealant of tetrafluoroethylene-ethylene copolymer having no reactivity with electrolyte, low moisture permeability, excellent chemical properties and good adhesiveness.

Electrochromic display element

Abstract: PURPOSE:To obtain a electrolytic soln type WO3 film display element having a long life usable in a wide temp range by using perchlorate, tetrafluoroborate or hexafluorophosphate of Na or Li as an electrolyte and ethylene glycol diacetate, etc as a solvent CONSTITUTION:A cell provided with display electrode leading portions 4, 7 and display substance layers 3, 6 made of WO3 film on glass substrates 1, 2, respectively is filled with electrolytic soln 5 consisting of one of LiClO4, NaClO4, LiPF6, NaPF6, LiBF4 and NaBF4 as an electrolyte and ethylene glycol diacetate, ethylcyanoacetate cyclohexanone, succinonitrile, dimethyl (ethyl) maleate, etc as a solvent

Solid state electrochromism in WO3

Abstract: ZrO2 and Ta2O5 films were used as solid electrolyte layers in electrocnromic cells of WO3 Measurement of the weight changes of those cells during coloration and bleaching suggested that water contained in the cells played an important role for the coloration Another kind of cell showed that it is not the water in WO3 layer but that in a solid electrolyte layer that is essential Reasons of deterioration of the electrochromic cells are not only a peeling Au electrode off from the cells but also a kind of morphologic changes of films

Characteristics of the electrochromic materials Au-Wo3 and Pt-Wo3

Abstract: The electrochromic cermet Au-WO3 is composed of grains of Au, approximately 20-120a in diameter, embedded in a matrix of amorphous WO3. As prepared, the cermet is blue and when electrochemically colored it is red or pink. The matrix must be amorphous in order for the red color to develop. In polycrystalline Au-WO3 films, the colored state is dark blue. We find that the properties of the amorphous WO3 matrix in the presence of Au are different from pure amorphous WO3. In particular, the presence of the Au grains suppresses the high electrical conductivity characteristic of colored WO3. Pt-WO3 cermets are compared and contrasted with Au-WO3. We discuss the optical and electrical properties of the Au-W03 cermets and their possible use in display devices.

Electrochromic device with transmissive counter electrode

Abstract: An improved counter electrode used in an electrochromic device is transmissive in both charge injection and extraction states and exhibits excellent reversibility whereby it is optimum as a counter electrode in a transmissive electrochromic device which is useful as a display device in its control of visible and infrared absorption by a window and the like.