Showing papers on "Electrochromism published in 1993"

Applications of electroactive polymers

Abstract: Preface. Electrical and electrochemical properties of ion conducting polymers. Electrical and electrochemical properties of electronically conducting polymers. Highly-conductive polymer electrolytes. Solvation mechanisms in low molecular weight polyethers. Lithium batteries with polymer electrodes. Lithium polymer batteries. Electrochromic devices. Laminated electrochromic displays and windows. Functionalized conductive polymer membranes/films. Electroactive polymers in chemical sensors.

Crystal Structure of the Polymer Electrolyte Poly(ethylene oxide)3:LiCF3SO3.

Abstract: Ionically conducting polymers (polymer electrolytes) are under intensive investigation because they form the basis of all solid-state lithium batteries, fuel cells, and electrochromic display devices, as well as being highly novel electrolytes. Little is known about the structures of the many crystalline complexes that form between poly(ethylene oxide) and a wide range of salts. The crystal structure is reported of the archetypal polymer electrolyte poly(ethylene oxide)(3):LiCF(3)SO(3), which has been determined from powder x-ray diffraction data. The poly(ethylene oxide) (PEO) chain adopts a helical conformation parallel to the crystallographic b axis. The Li(+) cation is coordinated by five oxygen atoms-three ether oxygens and one from each of two adjacent CF(3)SO(3)(-) groups. Each CF(3)SO(3)(-) in turn bridges two Li(+) ions to form chains running parallel to and intertwined with the PEO chain. There are no interchain links between PEO chains, and the electrolyte can be regarded as an infinite columnar coordination complex.

Transparent conductive electrodes for electrochromic devices: A review

Abstract: This paper reviews the optical and electrical performance of thin films that are useful as transparent electrodes in electrochromic devices. The properties of certain heavily doped wide-bandgap semiconductor oxides (especially In2O3:Sn) and of certain coinage metal films are discussed.

Electrochromic Reactions in Manganese Oxides I . Raman Analysis

Abstract: Like nickel oxide, manganese oxide is a widely studied material in the primary batteries field. The reactions taking place during voltametric cycling of manganese oxides can be determined using in situ Raman spectroscopy. The main difficulty for the oxide identification is to obtain relevant Raman reference spectra because of the many possible compounds and, for some of these compounds, of their instability in the laser beam. As a consequence, several modifications of different tetra-, tri- and divalent manganese oxides and oxyhydroxides were carefully studied. The electrochromic behavior of three types of manganese oxides, two prepared by thermal oxidations and the other by electrochemical deposition, were then compared. The presence of nonstoichiometry in the pristine material was necessary to obtain a reversible electrochromic effect. The reaction during electrochromic cycling is more complicated than a simple passage from MnO[sub 2] to MnOOH.

Transmission Spectra of an Electrochromic Window Based on Polyaniline, Prussian Blue and Tungsten Oxide

Abstract: The demand for energy savings in buildings will increase in the coming years, as the world`s attention is drawn towards environmental aspects and energy economizing. Windows which are able to dynamically control the sun radiation throughput will play an important role. In this respect, the authors have studied two different electrochromic window configurations; one based on the two complementary electrochromic materials polyaniline (PANI) and tungsten oxide (WO{sub 3}), the other one with the electrochromic coating Prussian blue (PB) in addition to PANI and WO{sub 3}. The inclusion of PB enhances the transmission modulation. Integrating over the solar spectrum they find that the window based on PANI and WO{sub 3} is able to regulate 39% of the total solar energy, while with the inclusion of PB they manage to regulate as much as 50% of the sun radiation.

Structure and Electronic Properties of Electrochromic NiO Films

Abstract: Nickel oxide films were deposited by reactive RF magnetron sputtering. Optical and electrochemical characterization showed strong electrochromic activity under certain deposition conditions. X-ray diffraction and infrared absorption measurements indicate that the films are polycrystalline NiO and that the bulk crystal structure does not change upon oxidation and reduction. Electronic conduction in the films and charge storage at the NiO/electrolyte interface were studied by dc resistance and ac impedance measurements. The infrared measurements and x-ray photoelectron spectroscopy were used to characterize changes in surface composition

Electrochromic materials and displays

Abstract: Dispersions of electrically conductive particles useful for preparing electrically conductive, essentially ionically isolative composite layers having electrically conductive particles dispersed in a polymer matrix. Composite layers can be used in laminates for electrochromic displays where an ionically conductive layer is in contact with electrochromic material. Such displays comprise means for applying an electrical potential across the interface of the ionically conductive layer and the electrochromic material to generate an electrochromic effect at the interface. Electrochromic materials can be provided in the laminates as layers between the ionically conductive layer and the composite layer of electrically conductive particles dispersed in a polymer matrix. Alternatively, the electrochromic material can be incorporated in the conductive particles in the polymer matrix, e.g. as titanium dioxide coated with antimony tin oxide coated with polyaniline dispersed in an light transmitting polymer matrix. The materials of this invention allow for the high speed fabrication of flexible displays, e.g. by printing methods.

Electrochromic materials: Microstructure, electronic bands, and optical properties

Abstract: Crystals of all the well known electrochromic metal (Me) oxides are composed of MeO6 octahedra in various corner-sharing and edge-sharing arrangements. Cluster-type and columnar microstructures, based on the MeO6 units, exist in electrochromic films. The coordination of the ions leads to schematic electronic band structures that, at least for the (defect) perovskite and rutile lattices, are able to explain the presence or absence of cathodic and anodic electrochromism. Small polaron absorption prevails in disordered oxides, while crystalline tungsten oxide can show free-electron effects.

Electrochromic structures and methods

Abstract: Electrochromic devices applied to a substrate (12) are disclosed, including an electrochromic electrode layer (20), a counterelectrode layer (24), and an ion-conducting layer (22) sandwiched between those two layers and electrically isolating them from each other, in which the ion-conducting layer (22) is substantially uniform across the substrate and comprises an inorganic superstructure with associated organic material and with a microstructure which facilitates the transfer of ions. Methods for producing these devices are also disclosed, including depositing the ion-conducting layer (22) on the substrate (12) in the form of a solution, and effecting gelation of that solution.

Preparation and Characterization of a Dip‐Coated SnO2 Film for Transparent Electrodes for Transmissive Electrochromic Devices

Abstract: A new method for the synthesis of SnO 2 is proposed and thin films are prepared by a dip-coating method. In the present paper we report that these SnO 2 films exhibit a reversible electrochemical insertion of lithium ions while maintaining high optical transmissivity. These films can be used as transparent counterelectrodes in electrochromic transmissive devices and in gas sensors

Electrochromic and gas adsorption properties of Langmuir-Blodgett films of lutetium bisphthalocyanine complexes

Abstract: The electrochromic behaviour, spectroscopic properties and gas chemisorption of ultra thin films of lutetium octa-4-phenyldiphthalocyanine (LuPc[sub 2][sup Ph]), and the lutetium octa-3-bromo-octa-5-tert-butylphthalocyanine (LuPc[sub 2][sup tBr]) are reported. Electrochromism was observed for Langmuir-Blodgett (LB) and films cast onto indium tin oxide (ITO) coated glass electrodes in aqueous KClO[sub 4] solution. Mixed LB films supported on ITO glass electrodes were more stable to repetitive cycling than cast films. Films of LuPc[sub 2][sup Ph] and LuPc[sub 2][sup tBr] were sensitive to electron-acceptor gases as observed by the changes in the electronic absorption spectra and the surface-enhanced resonance Raman scattering (SERRS) spectra. The presence of electron-withdrawing bromine atoms in the phthalocyanine ring increased the rate of desorption for chemisorbed electron-acceptor molecules. 10 refs., 8 figs., 3 tabs.

Radio frequency sputtered cobalt oxide coating: Structural, optical, and electrochemical characterization

Abstract: Cobalt oxide thin films (thickness 2000 A) with different stoichiometries were deposited by reactive rf sputtering. The variation of the oxygen partial pressure lead to films with compositions varying from metallic cobalt to CO3O4, as determined by x‐ray diffraction and x‐ray photoelectron spectroscopy. The electrochromic properties of the films were investigated in aqueous electrolytes (0.1 M KOH). The initial electrochemical behavior of the films is strongly dependent on the film deposition conditions, but after cycling the electrochemical/electrochromic characteristics of the different deposits were quite similar. Transmittance changes and electrochromic efficiency are discussed.

The influence of microstructure on the electrochromic properties of LixWO3 thin films: Part I. Ion diffusion and electrochromic properties

Abstract: The chemical diffusion coefficients of lithium ions in LixWO3 films were investigated as a function of lithium concentration and film porosity. Thin films were deposited with different porosities by thermal evaporation of WO3 powder in various partial water pressures. Our results indicate that diffusion coefficients increase with film porosity and decrease with increasing lithium concentration. Large diffusion coefficients that were found for small lithium concentrations appear to be due to the contribution of protons generated from ion exchange reactions between lithium and water incorporated in the film. Simultaneous electrical and in situ optical measurements were carried out to study the effect of porosity on the electrochromic properties of LixWO3. The coloring efficiency of porous WO3 films increases by approximately 70% when deposited in partial water pressure of 10−4 Torr, but decreases with further increments in water pressure.

Electrooptic response of smectic O and smectic O

Abstract: We present the results of our investigations on the electrooptic properties of the smectic O and O* phases of m7tac (1-methylheptyl terephthalylidene-bis-4-aminocinnamate). At low voltages, we observed striking electrochromic effects and, in O* at high voltages, a field induced phase transition. Freely suspended thick films of m7tac in the O and O* phases are weakly biaxial. A framework is proposed to account for our observations.

Variable reflectance mirror

Abstract: The present invention provides variable reflectance mirrors wherein the component of variable transmittance is a single-compartment, self-erasing, solution-phase electrochromic device.

Electrochromic properties of niobium oxide thin films prepared by radio‐frequency magnetron sputtering method

Abstract: Electrochromic niobium oxide thin films were prepared by a radio‐frequency magnetron sputtering method. Amorphous Nb2O5 thin films deposited at radio‐frequency power 100 W showed the electrochromic behavior: Reduction and oxidation of the films in 0.1 M Na2CO3+0.1 M NaHCO3 buffer solution resulted in coloration and bleaching, respectively. Coulometry indicated that the coloration efficiency was 10 cm2/C.

Effect of preparation conditions on the morphology and electrochromic properties of amorphous tungsten oxide films

Abstract: Electrochromic tungsten oxide thin films have been prepared by reactive dc‐magnetron sputtering under different deposition conditions. Through the use of electrochromic coloration and spectroscopic ellipsometry experiments, the effect of preparation conditions on film morphology and electrochromic properties has been studied. The results of this study are consistent with previous reports finding that amorphous tungsten oxide thin films are dominated by a columnar morphology and an intercolumnar void network that strongly influence the electrochromic properties. In addition real‐time spectroscopic ellipsometry (SE) experiments on the tungsten oxide electrochromic coloration process have been performed for the first time. In studies of very thin (∼15 nm) films by real‐time SE, the formation of tungsten bronze exhibits reaction‐limited kinetic behavior, and thus we are able to extract accurate dielectric function spectra for the film in different stages of the coloration process. These spectra can be understood in terms of a two‐phase physical mixture of tungsten oxide and tungsten bronze components with relative volume fractions determined in a regression analysis of the spectra.