Showing papers on "Electrochromic devices published in 2009"

Hexagonal Tungsten Oxide Based Electrochromic Devices: Spectroscopic Evidence for the Li Ion Occupancy of Four-Coordinated Square Windows

Abstract: Macroporous hexagonal WO3 (h-WO3) films were obtained at 400 °C from a sol containing tungstic acid with organically modified silane as a template. Asymmetric electrochromic devices based on the macroporous h-WO3 layer were constructed. XRD and micro-Raman studies of the intercalation/deintercalation of lithium into the h-WO3 layer of the device as a function of the applied voltages were performed. In h-WO3, Li+ can be intercalated into three potential sites: trigonal cavity (TC), hexagonal window (HW), and four-coordinated square window (SW). XRD measurements show systematic changes in the lattice parameter, which was associated with the amount of Li intercalated into the h-WO3 layer. Correspondingly, Raman spectroscopy shows that at 1.0 V Li+ completely fill TC and partially fill HW sites. For potentials ≥1.5 V, Li+ are inserted into the SW, as evidenced from the vanishing of the ν(O−W−O) Raman modes. The reversible characteristics of the device from optical measurements and Raman spectra demonstrated t...

Transparent TiO2 nanotube electrodes via thin layer anodization: fabrication and use in electrochromic devices.

Abstract: In the present work, we describe an anodization process that is able to fully transform a thin Ti metal layer on a conductive glass into a TiO2 nanotubular array. Under optimized conditions, nanotube electrodes can be obtained that are completely transparent and defect-free and allow electrochromic switching. These electrochromic electrodes show remarkable properties and can be directly integrated into devices.

The role of water in the synthesis and performance of vapour phase polymerised PEDOT electrochromic devices

Abstract: Parameters affecting the quality of vapour phase polymerised (VPP) PEDOT and their influence on electrochromic device performance were investigated. Specifically, the role of water during synthesis was examined and a polymerisation mechanism proposed. Paradoxically, water vapour is essential for PEDOT polymerisation, however, too high a loading leads to crystallite formation in the oxidant layer, rendering the oxidant inactive. Changes in water vapour affect the doping level of the polymer, presumably due to poor conjugation along the polymer's backbone during synthesis. The addition of a surfactant, PPG-ran-PEG, was studied using XPS. The surfactant inhibited oxidant crystal growth and slowed the rate of PEDOT polymerisation, reducing film defects and improving PEDOT conductivity. Controlling and optimising the levels of water vapour and surfactant during synthesis resulted in reproducible, high conductivity, high optical switch, PEDOT films. Finally, complementary dual-polymer electrochromic devices utilising (pre- and post-process-enhanced) VPP PEDOT and PMAS (control) were fabricated and changes in switching transmission evaluated.

High-Contrast Solid-State Electrochromic Devices of Viologen-Bridged Polysilsesquioxane Nanoparticles Fabricated by Layer-by-Layer Assembly

Abstract: Water-soluble silsesquioxane nanoparticles (NPs) incorporating viologen groups (PXV; 1,1′-bis[3-(trimethoxysilyl)propyl]-4,4′-bipyridinium iodide) have been synthesized by sol−gel polymerization. The electrochromic properties of the bulk film fabricated by layer-by-layer (LbL) assembly have been examined, along with their incorporation into solid-state devices. The orange LbL films show high thermal stability and exhibit a maximum UV−vis absorption at 550 nm. Electrochromic switching of the NPs in liquid electrolyte as well as in the solid state was evaluated by a kinetic study via measurement of the change in transmission (% T) at the maximum contrast. Cyclic voltammograms of the PXV NP LbL films exhibit a reversible reduction at −0.6 V vs Ag/AgCl in a 0.1 M NaClO4(aq) solution, revealing good electrochromic stability, with a color change from orange to dark purple-blue at applied potentials ranging from −0.7 to −1.3 V. Cathodically coloring PXV NP solid-state devices exhibit a switching time of a few se...

Electrochemistry of poly(3,4-ethylenedioxythiophene)-polyaniline/ Prussian blue electrochromic devices containing an ionic liquid based gel electrolyte film.

Abstract: Electrochromic devices based on poly(3,4-ethylenedioxythiophene) (PEDOT) as the cathodic coloring electrode and polyaniline (PANI) or Prussian blue (PB) as the counter electrode containing a highly conductive, self-supporting, distensible and transparent polymer–gel electrolyte film encapsulating an ionic liquid, 1-butyl-1-methylpyrrolidiniumbis(trifluoromethylsulfonyl)imide, have been fabricated. Polarization, charge transfer and diffusion processes control the electrochemistry of the functional electrodes during coloration and bleaching and these phenomena differ when PEDOT and PANI/PB were employed alternately as working electrodes. While the electrochemical impedance response shows good similitude for PEDOT and PANI electrodes, the responses of PEDOT and PB were significantly different in the PEDOT–PB device, especially during reduction of PB, wherein the overall amplitude of the impedance response is enormous. Large values of the coloration efficiency maxima of 281 cm2C−1 (λ = 583 nm) and 274 cm2C−1 (λ = 602 nm), achieved at −1.0 and −1.5 V for the PEDOT–PANI and PEDOT–PB devices have been correlated to the particularly low magnitude of charge transfer resistance and high polarization capacitance operative at the PEDOT–ionic liquid based electrolyte interface at these dc potentials, thus allowing facile ion-transport and consequently resulting in enhanced absorption modulation. Moderately fast switching kinetics and the ability of these devices to sustain about 2500 cycles of clear-to-dark and dark-to-clear without incurring major losses in the optical contrast, along with the ease of construction of these cells in terms of high scalability and reproducibility of the synthetic procedure for fabrication of the electrochromic films and the ionic liquid based gel electrolyte film, are indicators of the promise these devices hold for practical applications like electrochromic windows and displays.

Synthesis, characterization, and hierarchical organization of tungsten oxide nanorods: spreading driven by Marangoni flow.

Abstract: Tungsten oxide nanorods were synthesized by a soft chemistry approach using tungsten alkoxide and trioctyl amine and oleic acid as the surfactants. The optical properties of the nanorods were studied. The nanorods were found to be soluble in a wide range of solvents like chloroform, cyclohexane, and so on. Upon solvent evaporation, the nanorods formed hierarchically organized solid state structures. Depending on the solvent used, the nanorods organized in different mesostructures. Moreover, the organization of the nanorods from mixtures of polar and nonpolar solvents was studied. Here, the Marangoni effect resulting from differences in the surface tensions of the two solvents was found to play a role in the organization of the nanorods. Furthermore, dip coating of the nanorod solutions on a mica substrate resulted in the formation of a uniform thin film of the nanorods, which may be useful for a variety of applications such as in electrochromic devices and in organic light emitting devices (OLEDs) using tungsten oxide as a buffer layer.

Dual n- and p-Type Dopable Electrochromic Devices Employing Transparent Carbon Nanotube Electrodes

Abstract: We report on the use of highly transmissive single-walled carbon nanotube (SWNT) films as electrodes in electrochromic devices that employ a dual n- and p-type dopable donor−acceptor polymer, poly[5,8-bis-(3-dihydro-thieno[3,4-b][1,4]dioxin-5-yl)-2,3-diphenyl-pyrido[3,4-b]pyrazine], or poly(bisEDOT-PyrPyr-Hx2). This low bandgap polymer is capable of repeated, stable electrochemical cycling between a neutral form and both an oxidized, p-doped state and a reduced, n-doped state. The ability of this electrochromic material to exhibit a stable n-type doped state enabled the construction of an absorptive/transmissive dual-window electrochromic device showing optical changes over a broad energy range—from the mid-infrared to the visible region. This absorptive/transmissive dual polymer electrochromic device is unique in that it exhibits electrochromism utilizing the same polymer as both the cathodically and anodically coloring material. Infrared electrochromic behavior was achieved with the use of SWNT films du...

Synthesis and Characterization of Regioregular Water-Soluble 3,4-Propylenedioxythiophene Derivative and Its Application in the Fabrication of High-Contrast Solid-State Electrochromic Devices

Abstract: Water-soluble sulfonated monomer based on 3,4-propylenedioxythiophene (ProDOT-sultone) was synthesized and characterized for the first time via the O-alkylation of the corresponding unreactive β,β-disubstituted hydroxyl group with propane sultone in the presence of a catalytic amount of 1,4-diazabicyclo[2.2.2]octane (DABCO). This new monomer was oxidatively polymerized to produce regioregular water-soluble conjugated anionic polyelectrolyte, which was then used for the fabrication of solid-state electrochromic devices using the layer-by-layer (LbL) deposition method. These solid-state devices were found to exhibit better electrochromic properties in terms of color contrast, switching time, coloration efficiency (CE), surface control electroactivity, and conductivity in thin films compared with the corresponding water-soluble regiorandom 3,4-ethylenedioxythiophene (EDOT) derivative. For the 40 and 80 bilayer solid-state electrochromic devices, the electrochemical contrast was observed to be 31 and 40% at 5...

Polythieno[3,4-b]thiophene as an Optically Transparent Ion-Storage Layer

Abstract: Ion storage layers have been employed in the construction of electrochromic devices to enhance device lifetimes through balanced ion shuttling. This has led to a search for a material which has a high charge capacity as well as optical transparency. Poly(thieno[3,4-b]thiophene) (PT34bT) exhibits high transparency in the visible region in both its neutral and oxidized states, in addition to having a high charge capacity, making it an ideal candidate for an ion storage layer. Herein we report devices fabricated by electrodeposition of several common chromophores, such as PEDOT, PDiBz-ProDOT, and PProDOT-Me2. Devices were made with and without a balanced layer of PT34bT on the counter electrode and were probed for coloration and contrast. It was found that the addition of the ion storage layer did not alter the color of any of the devices and resulted in a minimal, predicted loss of contrast corresponding to the thickness of the ion storage layer.

Electrochromic TiO2, ZrO2 and TiO2–ZrO2 thin films by dip-coating method

Abstract: Sol-gel processing of TiO2, ZrO2 and mixed Ti/Zr oxide thin films has been studied as application of these coatings in electrochromic devices. Their structural transformations as a function of annealing temperatures were analyzed by XRD and FTIR techniques. Electrochromic behavior of the three kind materials was investigated by cyclic voltammetry and the basic electrochromic characteristics were determined.

Glass laminated articles and layered articles

Abstract: Laminated articles and layered articles, for example, low alkali glass laminated articles and layered articles useful for, for example, electrochromic devices are described.

Fabrication of Nanotube Thin Films and Their Gas Sensing Properties

Abstract: The fabrication process and the growth mechanism of titanium/titania nanotubes prepared by anodization process is reviewed, and their applications in the fields of dye sensitized solar cells, photocatalysts, electrochromic devices, gas sensors, and biomaterials are presented. The anodization of Ti thin films on different substrates and the growth process of anodic titanium oxide are described using the current-time curves. Special attention is paid on the influences of the initial film smoothness on the resulted nanoporous morphologies. The “threshold barrier layer thickness model” is used to discuss the growth mechanism. As a case study for gas sensing, anodized highly ordered nanotube arrays and nanoporous thin films that show porous surface with an average diameter of 25 nm and interpore distance of 40 nm were prepared. Gas sensors based on such nanotube arrays and nanoporous thin films were fabricated, and their sensing properties were investigated. Excellent gas sensing properties were obtained for sensors prepared from these highly ordered nanotube arrays, which present stable response even at a low operating temperature of . Based on our experimental results, “H-induced desorption” mechanism was used for explaining the hydrogen gas sensing mechanism.

Development of Electrochromic Devices

Abstract: Electrochromic devices (ECD) are systems of considerable commercial interest due to their controllable transmission, absorption and/or reflectance. For instance, these devices are mainly applied to glare attenuation in automobile rearview mirrors and also in some smart windows that can regulate the solar gains of buildings. Other possible applications of ECDs include solar cells, small- and large-area flat panel displays, and frozen food monitoring and document authentication also are of great interest. Over the past 20 years almost 1000 patents and 1500 papers in journals and proceedings have been published with the key words "electrochromic windows". Most of these documents report on materials for electrochromic devices and only some of them about complete electrochromic devices. This paper describes the first patents and some of the recent ones on ECDs, whose development is possible due to the advances in nanotechnology.

Organically Soluble Bifunctional Polyaniline–Magnetite Composites for Sensing and Supercapacitor Applications

Abstract: Conducting polymers CPs now own a special status in the field of electroactive materials, especially after the pioneering and noble prize winning work by Shirakawa et al. 1 A great deal of progress has been made on these synthetic metals in terms of their synthesis, processability, and device applications. 2-4 Particular attention on polyaniline PAni has been given due to its environmental stability, thin-film–forming property with tunable conductivity and commercial viability. Polyanilines have been studied extensively due to their applications to practical devices for energy storage, electrochemical sensors, electrochromic devices, electromagnetic interference shielding, and corrosion protection. 3-10 Application of the CPs in energy storage devices is also well known, 11 and recent studies 12 in this area gave impetus to fundamental and applied research on CPbased materials. Recent literature 13 identified the polyaniline composite materials as potential electrochemical sensors for various biomolecules. Applications of conducting polymers are broadened by compositing with other inorganic materials. For example, polyaniline-metal nanoparticle composites exhibit enhanced sensing and catalytic properties, compared to pure polyaniline. 14-19 Apart from the properties mentioned above, conducting polymers are useful as magneto/ electrorheological ER materials/fluids. 20-23 ER fluids is a class of materials whose rheological characteristics are controllable through the application of an electric field. ER fluids are usually made of particle suspensions with a large dielectric constant mismatch between the particles and the fluid. Because of the controllable rheological properties, ER fluids can potentially be used as a smart material for active devices, which transform electric energy to mechanical energy. Polyaniline can change its property from a conducting to an insulating state using simple protonic acid treatment. This allows for a change in dielectric constant and conductivity of particles while keeping all other particle properties the same. In the present communication, we report the synthesis of organically soluble bifunctional polyaniline-magnetite composites, which can sense dopamine and also act as supercapacitor electrode material. The results are presented and discussed.

Composite electrode and electrolytes comprising nanoparticles and resulting devices

Abstract: This invention discloses novel electrochromic devices and polymer actuator materials where nanoparticles are used to make composites. In particular, the said nanoparticles are wire shaped and disc shaped. These composites allow EC devices to be made with improved performance, particularly display devices could be made that consume low power and can be manufactured at low cost.

Method for manufacturing electrochromic devices

Abstract: This invention contemplates the use of laser patterning/scribing in electrochromic device manufacture, anywhere during the manufacturing process as deemed appropriate and necessary for electrochromic device manufacturability, yield and functionality, while integrating the laser scribing so as to ensure the active layers of the device are protected to ensure long term reliability. It is envisaged that the laser is used to pattern the component layers of electrochromic devices by directly removing (ablating) the material of the component layers. The invention includes a manufacturing method for an electrochromic device comprising one or more focused laser patterning steps. To minimize redeposition of laser ablated material and particulate formation on device surfaces a number of approaches may be used: (1) ablated material generated by the focused laser patterning may be removed by vacuum suction and/or application of an inert gas jet in the vicinity of the laser ablation of device material; (2) spatial separation of the edges of layers and patterning of lower layers prior to deposition of upper layers; and (3) the laser patterning step may be performed by a laser beam focused directly on the deposited layers from above, by a laser beam directed through the transparent substrate, or by a combination of both.

Studies on the correlation between electrochromic colouration and the relative density of tungsten trioxide (WO3−x) thin films prepared by electron beam evaporation

Abstract: The colouration efficiency in the electrochromic devices depends upon the amount of intercalating charge in the tungsten oxide (WO3−x) thin films. One of the physical properties of the film that significantly influence the intercalating charge is the film density. In this paper, the dependence of intercalated charge in WO3−x thin films on the film density is reported. The amorphous tungsten oxide thin films have been prepared by electron beam evaporation at three substrate temperatures: 300, 470 and 570 K. With increasing substrate temperature, the refractive indices of the films increase. The relative film density calculated from the refractive index using the Lorentz–Lorentz relationship increases with the substrate temperature. With increasing density of the WO3 thin films, the diffusion coefficients of protons and the amount of intercalated charge decrease. The intercalated charge in the coloured electrochromic thin films brings about a change in the surface work function of the thin film; the difference in the surface work function (between the coloured and the bleached states) is measured by the Kelvin probe. In the present investigation, an intercalating charge of 59, 48 and 39 mC cm−2 brings about a change of 0.24, 0.16 and 0.13 eV in the surface work function of the WO3 thin films.