Showing papers on "Electrochromism published in 2000"

Organic materials for electronic and optoelectronic devices

Abstract: This article concentrates on our recent results on several classes of photo- and electro-active organic materials that permit thin film formation and discusses their synthesis, properties, functions and potential applications for electronic and optoelectronic devices. The materials studied include amorphous molecular materials, titanyl phthalocyanine, oligothiophenes with well-defined structures, and non-conjugated polymers containing pendant oligothiophenes or other π-electron systems. The thin films of these materials find potential applications for use in organic electroluminescent, photovoltaic, electrochromic, and other devices.

Manganese Oxide Thin Film Preparation by Potentiostatic Electrolyses and Electrochromism

Abstract: Manganese oxide thin films were deposited on transparent conducting tin oxide glass substrates by potentiostatic anodic electrolysis of alkaline solution of a manganese ammine complex at 298 K. The effects of varying deposition potentials on the microstructure and the electrochromic (EC) properties of the films were investigated. Characterization of films by X‐ray diffraction revealed that two distinct potential regions (lower and higher than 0.3 V vs. Ag/AgCl) were available for the film deposition; the crystal structure of the film deposited at lower and higher regions were and/or and , respectively. X‐ray photoelectron spectroscopy (XPS) analyses of the films featuring exchange splitting effect on Mn 3s spectra indicated that the valence of manganese in the films prepared at lower and higher potential regions are mixtures of divalence‐trivalence and of trivalence‐tetravalence, respectively. The XPS analysis also revealed that terminal chemical bonding species of the films are a mixture of hydroxide (Mn‐O‐H) and oxide (Mn‐O‐Mn). The mechanism of the EC process, by which the color change between brown and light yellow occurs, could be explained in terms of the transformation between these two oxygen groups in Mn‐O‐H and Mn‐O‐Mn, accompanied by the change in valence of Mn. The EC durability of the films in switching performance was also assessed. © 2000 The Electrochemical Society. All rights reserved.

Ultrafast electrochromic windows based on redox-chromophore modified nanostructured semiconducting and conducting films

Abstract: Described is the construction of an ultrafast electrochromic window. One electrode of this window is based on a transparent nanostructured TiO2 (anatase) film (4.0 mum. thick) supported on conducti ...

In situ colorimetric analysis of electrochromic polymers and devices

Abstract: We report a colorimetric method for the in situ study of electrochromic polymers based on the CIE system of colorimetry. This method is useful for the comparison of the electrochemical and optical properties of conjugated polymers, and for gaining control of the color of dual polymer electrochromic devices. Twelve electrochromic polymers were investigated using in situ colorimetric analysis in order to define their CIE coordinates and electrochemical potential windows. By controlling the electron density and steric interactions along conjugated polymer backbones, we have developed a set of electrochromic polymers that provides colors throughout the full range of color space. The applicability of the method is illustrated with a model dual polymer device based on poly(2-(3,4-ethylenedioxy)thienyl(biphenyl)) (PBEDOT-BP) and poly(3,6-bis(3,4-ethylenedioxy)thienyl)-N-methylcarbazole) (PBEDOT-NMeCz). This device yields green/brown colors (L* = 48, a* = 0, b* = 20 and L* = 44, a* = 6, b* = 26) interesting for e...

Poly(3,4-alkylenedioxypyrrole)s: Highly Stable Electronically Conducting and Electrochromic Polymers

Abstract: A series of poly(3,4-alkylenedioxypyrrole)s are reported as a new class of electronically conducting polymers exhibiting especially low oxidation potentials from ca. −0.6 to −0.4 V vs Fc/Fc+ (equivalent to −0.15 to +0.05 V vs SCE) as desired for ambient stability of the doped and conducting states. These polymers exhibit unique combinations of multicolor electrochromism, switching from a red or orange neutral state to a light blue/gray doped state, passing through a darker intermediate state (brown), as examined by in situ colorimetry. High spectral contrast ratios have been measured throughout the visible region with a maximum Δ%T = 76% at 534 nm for poly[3,4-(2,2-dimethylpropylenedioxy)pyrrole) (PProDOP−(CH3)2). PProDOP−(CH3)2 exhibits outstanding redox switching stability, being able to undergo 40 000 deep double-potential switches between its doped and neutral states (1 s, Δ%Tmax = 76%) while retaining more than 90% of its electroactivity. A high level of stability to overoxidation has also been obser...

Nanocrystalline Tungsten Oxide Thin Film: Preparation, Microstructure, and Photochromic Behavior

Abstract: A nanocrystalline tungsten oxide photochromic thin film was prepared by colloid chemistry method. The microstructure, phase transition involved in the solution process, photochromic behavior, and mechanism of the film were investigated by means of transmission electron microscope, x-ray diffraction, ultraviolet-visible absorption spectra, and x-ray photoelectron spectra. It was found that the particle size and crystallinity of the thin film could be easily controlled by adjusting the concentration of oxalic acid in the colloid solution of tungsten oxide hydrate. With the increase of the oxalic acid concentration, the size of nanoparticles in the film decreased sharply, and meanwhile, a blue shift of the absorption peaks caused by the quantum size effect was observed accordingly. With the increase of the pH in the solution, tungsten oxide hydrate was gradually transformed into an oxided 12-tungstate with Keggin structure, which led to the change of photochromic property of the films. The photochromism of the film is believed to be due to the electron transfer between the different valence states of tungsten ions located in adjacent sites.

Color-stabilized electrochromic devices

Abstract: An electrochromic medium for use in a normally operating electrochromic device comprising an anodic material and a cathodic material wherein both of the anodic and cathodic materials are electroactive and at least one of the anodic and cathodic materials is electrochromic, an additive, and means associated with the additive for maintaining a colorless or nearly colorless electrochromic medium while the electrochromic medium is in a high transmission state relative to an electrochromic medium without the additive.

Electrochromic media with concentration-enhanced stability, process for the preparation thereof and use in electrochromic devices

Abstract: Increased stability of electrochromic devices containing an electrochromic medium having two or more electroactive compounds is accomplished by establishing current limiting concentrations of electroactive compounds with the larger redox potential difference. A process for production of electrochromic devices uses targeted concentrations of electroactive materials during preparation of the electrochromic medium which results in substantially no devices being produced wherein the current is limited by an electroactive compound having a low redox potential difference.

Electrochromism of Highly Doped Nanocrystalline SnO2:Sb

Abstract: The electrochromic effect of layers of nanocrystalline tin dioxide highly doped with antimony has been investigated in detail, using chronoamperometry, cyclic voltammetry, potential-dependent IR spectroscopy and UV−vis spectroscopy. It is shown that two different mechanisms are responsible for the color changes observed upon negative polarization of porous SnO2:Sb nanocrystal layers. Injection of electrons via the back contact increases the plasma absorption of the material, which has its maximum intensity in the near-infrared region. This increase is accompanied by a strong increase of the electrical conductivity of the layer, indicating that the grain boundary potentials of the nanoparticle layer decrease at negative potentials applied. In the presence of small ions such as Li+ or in protic electrolytes such as water, insertion of Li+ and H+ takes place, resulting in an additional color change mainly in the visible. The rate of the color changes is mainly determined by the conductivity of the substrate....

Alternating current impedance and Raman spectroscopic study on electrochromic a-WO3 films

Abstract: The chemical diffusion of lithium ions in a-LixWO3 films is investigated using alternating current impedance spectroscopy and Raman scattering measurements. The diffusion coefficients increase with increasing x in a-LixWO3 up to x=0.072 and then decrease. Raman measurements show that the W6+=O/O–W6+–O ratio also increases at the early stage of lithium insertion and then decreases with further lithium insertion. We conclude that the diffusion kinetics of lithium ions in a-LixWO3 films is very closely related to the W6+=O/O–W6+–O ratio.

Infrared switching electrochromic devices based on tungsten oxide

Abstract: Different types of electrochromic devices for thermal emittance modulation were developed in the spectral region from mid- to far-infrared (2–40 μm). In all devices polycrystalline and amorphous tungsten oxide have been used as electrochromic and ion storage layer, respectively. Two types of all-solid-state devices were designed, one with a metal grid for the top and bottom electrode deposited on a highly emissive glass substrate, and another with a top metal grid electrode and a highly reflecting bottom metal electrode layer. Tantalum oxide is used as an ion conductor in both device types. The third device type consists of a polymeric ion conductor. All solid-state constituent layers were grown by either reactive or nonreactive dc or rf magnetron sputtering in a high vacuum environment. Modulation of the emittance is accomplished by reversible insertion of Li ions into polycrystalline WO3 by applying and switching a small voltage across the structure. Spectrally dependent measured reflectance modulation of the device has been used to determine the device emissivity modulation with respect to the blackbody emissivity spectra at 300 K. Best device performance was found in both solid-state devices showing an emissivity modulation of about 20%.

Seal for electrochromic devices

Abstract: An improved seal member is provided as a part of an electrochromic device to bond two glass elements together in a spaced-apart relationship. In one embodiment the seal member provides improved adhesion to a reflector/electrode on the third surface of an electrochromic mirror, or to a layer of metal on the second or third surface for an electrochromic light filter. This seal member comprises a mixture of an organic resin scaling system and an adhesion promoter, where the adhesion promotor comprises a first and a second region, where the first region interacts with the reflector/electrode or the metal layer, and a second region that interacts with the organic resin sealing system, and may even chemically react with the organic resin sealing system. In another embodiment the seal member is provided with a coefficient of thermal expansion that is closer to glass than a standard epoxy sealing system.

Electrochromic Linear and star branched poly(3,4-ethylenedioxythiophene-didodecyloxybenzene) polymers

Abstract: New linear and star structured poly(3,4-ethylenedioxythiophene−didodecyloxybenzenes) (PEBs) have been prepared which exhibit thermochromism and multicolor electrochromism as they are able to produce the three basic colors in the RGB system: red, green, and blue. The star polymer features a conjugated hyperbranched poly(triphenylamine) core with PEB arms ca. 8−10 repeat units (16−20 rings) in length. Red in solution, the optical spectra of both polymers exhibit a maximum absorption at 455 nm in the neutral state. Linear and star PEB are thermally stable up to 300 °C as demonstrated by TGA. The presence of an EDOT-phenylene repeat in the conjugated backbone results in a relatively low half-wave potential of +0.20 V vs Fc/Fc+, which is lower than regioregular poly(3-hexylthiophene) by 0.4 V and only slightly higher than PEDOT. As a result, star PEB is the first representative of a new class of star-shaped polymers where it is possible to address the electroactive arms independently from the conjugated core....

Electrochromic transparency incorporating security system

Abstract: An electrochromic window assembly includes a security system for monitoring breakage of the electrochromic window assembly. Control circuitry is connected to the electrochromic window assembly for monitoring an electrical characteristic of one or more conductive coatings within the electrochromic window assembly, such as electrical resistance. Upon detecting a change in the electrical resistance, such as that caused by a break in one or more conductive coating, an alarm signal is generated and is sent to an alarm trigger circuit for activating an alarm. A method for monitoring penetration or breakage of an electrochromic window assembly is also provided, which method involves applying electrical activation to an electrochromic assembly and monitoring for a change in an electrical characteristic based on the applied electrical potential. Electrochromic window assemblies incorporating security alarm features in accordance with the present invention are particularly useful in automobile applications.

A variable optical attenuator operating in the near-infrared region based on an electrochromic molybdenum complex

Abstract: A dinuclear oxo-Mo(V) complex 1 has been prepared which develops an intense absorption in the near-IR region (λ = 1340 nm; e = 23 000 M-1 cm-1) on reversible one-electron oxidation to [1]+. This has formed the basis of a variable optical attenuator, whereby the intensity of near-IR laser light may be modulated over a range of 50 dB according to the electrical potential applied to the cell.

Electrochromism in copper oxide thin films

Abstract: Transparent thin films of copper(I) oxide prepared on conductive SnO2:F glass substrates by anodic oxidation of sputtered copper films or by direct electrodeposition of Cu2O transformed reversibly to opaque metallic copper films when reduced in alkaline electrolyte. In addition, the same Cu2O films transform reversibly to black copper(II) oxide when cycled at more anodic potentials. Copper oxide-to-copper switching covered a large dynamic range, from 85 percent and 10 percent photopic transmittance, with a coloration efficiency of about 32 cm2/C. Gradual deterioration of the switching range occurred over 20 to 100 cycles. This is tentatively ascribed to coarsening of the film and contact degradation caused by the 65 percent volume change on conversion of Cu to Cu2O. Switching between the two copper oxides (which have similar volumes) was more stable and more efficient (CE = 60 cm2/C), but covered a smaller transmittance range (60 percent to 44 percent T). Due to their large electrochemical storage capacity and tolerance for alkaline electrolytes, these cathodically coloring films may be useful as counter electrodes for anodically coloring electrode films such as nickel oxide or metal hydrides.

Electrochromic mirror assembly

Abstract: An electrochromic mirror assembly is described that is substantially resistant to seal breaches caused by dendrite formation along adjacent layers of the laminate structure of the assembly. The laminate structure is preferably assembled in a water free environment and includes materials that prevent or inhibit the formation of dendrites between adjacent layers of the laminate structure. By way of a non-limiting example, an electrically conductive layer comprised of gold-containing material is disposed between the adhesive layer and the glass layer so as to prevent ionic migration from the reflective layer through a terminal strip.

Electrochromic medium having a color stability

Abstract: An electrochromic window assembly is disclosed that includes a first substrate and a second substrate that is maintained in a parallel and spaced relation from the first substrate by means of a window frame and spacer. The window assembly further includes an electrochromic device mounted within the airtight chamber formed between the first and second substrates. Electrochromic device 22 may be mounted so as to provide an air chamber between first substrate 12, which is the external substrate, and electrochromic device 22. At least one of the chambers formed between substrates 12 and 14 and electrochromic device 22 may be filled with an insulating gas such as argon. Also disclosed are novel methods for manufacture of an electrochromic device for incorporation into such a window assembly. A novel electrochromic device is also disclosed having electrical bus clips secured about the entire periphery of the electrochromic device. Also disclosed is the use of steel bus clips for the electrochromic device.