Showing papers on "Electrochromic devices published in 2011"

Multistage Coloring Electrochromic Device Based on TiO2 Nanotube Arrays Modified with WO3 Nanoparticles

Abstract: WO3 nanoparticles loaded in TiO2 nanotube arrays, fabricated by a chemical bath deposition (CBD) technique in combination with a pyrolysis process, is uniform and the diameter can be easily adjusted by the deposition times. The resultant hybrid nanotubes array shows a multistage coloring electrochromic response at different potential bias. The formation of a 3-dimensional WO3/TiO2 junction promotes unidirectional charge transport due to the one-dimensional features of the tubes, which leads to the significant positive-shift onset potential of the cathodic reaction (ion insertion) and the highly increased proton storage capacity. Compared to non-decorated nanotube arrays, the enhanced electrochromic properties of longer lifetime, higher contrast ratio (bleaching time/coloration time), and improved tailored electrochromic behavior could be achieved using the composite films.

Material Strategies for Black-to-Transmissive Window-Type Polymer Electrochromic Devices

Abstract: Black-to-transmissive switching polymer electrochromic devices (ECDs) were designed using a set of spray-processable cathodically coloring polymers, a non-color-changing electroactive polymer poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate) (PTMA) as the charge-compensating counter electrode, and a highly conducting gel electrolyte (6.5 mS cm−1). The color “black” was obtained by utilizing (1) individual copolymers absorbing across the visible spectrum, and (2) blends and bilayers of several polymer electrochromes with complementary spectral absorption. Neutral-state black and ink-like dark purple-blue (or “ink-black”) donor−acceptor (DA) copolymers composed of the electron-donor 3,4-propylenedioxythiophene (ProDOT) and the electron-acceptor 2,1,3-benzothiadiazole (BTD) building units, which possess relatively homogeneous absorption profiles across the visible spectrum, were chosen for their propensity to switch to transmissive states upon electrochemical oxidation. A blend of magenta and cyan po...

Layer-by-layer assembled solid polymer electrolyte for electrochromic devices

Abstract: A new solid polymer electrolyte film fabricated by layer-by-layer (LbL) assembly is presented. The electrolyte film consists of four interbonding layers per deposition cycle, which combines electrostatic and hydrogen bonding in the same structure. Linear poly(ethylene imine) (LPEI) and poly(ethylene oxide) (PEO) are used to enhance the dissolution of lithium salt and the ionic transport through segmental motions of polymer chains. Characterization of film structure and growth shows good incorporation of electrostatic and hydrogen bonding, because of the versatile control of the ionization of poly(acrylic acid) (PAA), which serves as a bridging molecule. Ionic conductivity values, as described by the Vogel−Fulcher−Tammann equation, are found to be above 10−5 S/cm for the dried electrolyte at room temperature and moderate humidity (52%RH). Thermal analysis reveals two competing processes, namely, cross-linking of LPEI and PAA to form an amide compound and segregation of PEO crystalline phase, which results ...

Enhanced electrochromic performance of composite films by combination of polyoxometalate with poly(3,4-ethylenedioxythiophene)

Abstract: A composite film containing poly(3,4-ethylenedioxythiophene) (PEDOT), polyoxometalate (POM) clusters K6P2W18O62·14H2O (P2W18) and polyallylamine hydrochloride (PAH) was fabricated by a smart combination of layer-by-layer (LbL) with electro-polymerization methods. The composite film displays enhanced electrochromic performance by incorporation of P2W18 into the PEDOT film. The electrochromic property of the film is significantly improved, resulting in an optical contrast of 54.7% at 600 nm and an absorbance that does not change after 1500 cycles. Additionally, the film provides broader absorption throughout the visible region. These results demonstrate the essential role of POMs in improving functionality on PEDOT for applications in electrochromic devices.

A simple, low waste and versatile procedure to make polymer electrochromic devices

Abstract: Herein we present a simple and elegant method for the creation of solid-state conjugated polymer devices. Their electrochromic properties were fully explored in this study, but one could envision the extension of this method to displays, solar cells, OLEDs, transistors, or many other applications. We prepared conductive polymer composites or blends within a polymer electrolyte using electrochemical polymerization of these monomers inside an assembled solid-state device. This method will work for any monomer that can be dissolved in the gel electrolyte. This technique offers simplicity in device construction, is easily adapted to patterned systems and comprises a low-waste assembly process. Our novel approach of assembling polymer electrochromic devices avoids the tedious cleaning process of the substrates, produces almost no waste, and by inkjetting insulating materials to mask the substrates, letters and high-resolution images could be achieved inside the converted polymer devices. Electrochromic devices utilizing PEDOT assembled by our method showed compatible switching speed and durability with a slightly higher contrast ratio.

Electronic Structure of Transparent Conducting Oxides

Abstract: Metallic oxides are a materials class showing one of the greatest range of properties – superconducting, ferroelectric, ferromagnetic [1], multiferroic, magneto-resistive, dielectric, or conducting. Of particular interest are the so-called transparent conducting oxides (TCOs) and amorphous semiconducting oxides (ASOs). The TCOs are heavily used for flat panel displays, photovoltaic cells, low emissivity windows, electrochromic devices, sensors and transparent electronics [2, 3, 4]. Oxides are of particular interest because the metal-oxide bond is strong so that the oxides have a combination of a high heat of formation and a wide band gap, compared to any similar compound.

Flexible Electrochromic Devices Based on Optoelectronically Active Polynorbornene Layer and Ultratransparent Graphene Electrodes

Abstract: Novel electrochromic polynorbornenes poly(NBPYTPAM) and poly(HNBPYTPAM), containing electroactive chromophores, were prepared via ring-opening metathesis polymerization (ROMP) from a new norbornene derivative (NBPYTPAM) using Grubbs’ catalyst and followed by hydrogen reduction. The glass transition temperatures (Tg) of poly(NBPYTPAM) and hydrogenated poly(HNBPYTPAM) were 190 and 175 °C, respectively. The cyclic voltammogram of the poly(HNBPYTPAM) film cast onto flexible graphene-coated polyethylene terephthalene (PET) substrates exhibited two reversible oxidation redox couples at 1.0 and 1.9 V. Flexible electrochromic devices were fabricated from the electroactive polymers and graphene-coated PET substrates. The electrochromic characteristics of poly(HNBPYTPAM) showed excellent stability and reversibility, with multistaged color changes from its yellow neutral form to green and then to dark-blue.

Electrochromic properties of large-area and high-density arrays of transparent one-dimensional β-Ta2O5 nanorods on indium-tin-oxide thin-films

Abstract: We report on the synthesis, crystalline structure, and electrochromic properties of transparent one-dimensional (1D) orthorhombic (β) Ta2O5 nanorods grown in a large-area high-density array. The transparent 1D β-Ta2O5 nanorod array was synthesized on a conducting indium-tin-oxide thin-film via hot-filament metal-oxide vapor deposition. The array contained ∼1900 β-Ta2O5 nanorods per square micrometer, which were on average, ∼17 nm wide and ∼300 nm long. The good coloration/bleaching cycles, large ion-diffusion coefficient (∼2.35×10−8 cm2/s), and high reversibility (∼79.8%) demonstrate that the 1D β-Ta2O5 nanorods to be a potential electrochromic material for electrochromic devices or smart windows.

Flame synthesis of tungsten oxide nanostructures on diverse substrates

Abstract: One-dimensional (1D) tungsten oxide nanostructures show great potential for applications in the areas of batteries, photoelectrochemical water-splitting, electrochromic devices, catalysts and gas sensors. 1D tungsten oxide nanostructures are currently synthesized by physical or chemical vapor deposition, which are limited by low temperatures, the need for vacuum conditions, frequently expensive catalysts, and difficulty in scaling up for mass-production. These limitations, however, can be overcome by flame synthesis. Here, using a co-flow multi-element diffusion burner, we demonstrate the atmospheric, catalyst-free, rapid, mild and scalable flame synthesis of diverse, quasi-aligned, large density, and crystalline tungsten oxide nanostructures on a variety of substrates. Specifically, under fuel-rich conditions, monoclinic 1D W 18 O 49 nanowires and nanotubes were grown on tungsten, iron, steel and fluorinated tin oxide (FTO) substrates, with controlled diameters ranging from 10 to 400 nm and axial growth rates ranging from 2 to 60 μm/h. Monoclinic 1D WO 3 nanowires and nanotubes were grown, instead, on silicon and silicon dioxide substrates. Under fuel-lean conditions, diverse WO 3 nanostructures, including monoclinic 1D nanowires, cubic 2D nanobelts and monoclinic 3D nanocones were grown on tungsten and FTO substrates. The success of this versatile flame synthesis method is attributed to the large tunability of several synthesis parameters, including the flame stoichiometry, the tungsten source and growth substrate temperatures, the tungsten oxide vapor concentration, and the material of the growth substrate. This flame synthesis method can be extended to synthesize other 1D transition metal oxides as well, enabling many large-scale electronic and energy conversion applications.

Lamination of electrochromic device to glass substrates

Abstract: PROBLEM TO BE SOLVED: To provide an electrochromic device laminate in which the occurrence of a crack or split due to the temperature difference between a glass central part and an edge part generated by sunlight absorption is suppressed, and a manufacturing method of the same.SOLUTION: After a plurality of electrochromic device precursors 21 are manufactured on an electrochromic glass substrate 31 and a spacer 27 is formed between the electrochromic device precursors, a step of cutting the electrochromic glass substrate in order to form individual electrochromic devices 30 includes cutting the electrochromic glass substrate along the spacer between the electrochromic device precursors. Each of the individual electrochromic devices is laminated on individual external laminate glass plates 22.SELECTED DRAWING: Figure 1b

High ionic conductivity P(VDF-TrFE)/PEO blended polymer electrolytes for solid electrochromic devices

Abstract: Solid polymer electrolytes with excellent ionic conductivity (above 10−4 S cm−1), which result in high optical modulation for solid electrochromic (EC) devices are presented. The combination of a polar host matrix poly(vinylidene fluoride-trifluoroethylene) P(VDF-TrFE) and a solid plasticized of a low molecular weight poly(ethylene oxide) (PEO) (Mw ≤ 20 000) blended polymer electrolyte serves to enhance both the dissolution of lithium salt and the ionic transport. Calorimetric measurement shows a reduced crystallization due to a better intermixing of the polymers with small molecular weight PEO. Vibrational spectroscopy identifies the presence of free ions and ion pairs in the electrolytes with PEO of Mw ≤ 8000. The ionic dissolution is improved using PEO as a plasticizer when compared to liquid propylene carbonate, evidently shown in the transference number analysis. Ionic transport follows the Arrhenius equation with a low activation energy (0.16–0.2 eV), leading to high ionic conductivities. Solid electrochromic devices fabricated with the blended P(VDF-TrFE)/PEO electrolytes and polyaniline show good spectroelectrochemical performance in the visible (300–800 nm) and near-infrared (0.9–2.4 μm) regions with a modulation up to 60% and fast switching speed of below 20 seconds. The successful introduction of the solid polymer electrolytes with its best harnessed qualities helps to expedite the application of various electrochemical devices.

Series connected electrochromic devices

Abstract: An electrochromic device includes a first electrochromic region interconnected with a second electrochromic region by a plurality of conductive links disposed between sides of a substrate on which the material layers of the electrochromic device are formed. The plurality of conductive links interconnects a first isolated conductive region of the first electrochromic region with a first isolated conductive region of the second electrochromic region. A sequence of a counter electrode layer, an ion conductor layer and an electrochromic layer is sandwiched between the first conductive regions of the first and second electrochromic regions and respective second isolated conductive regions of the first and second electrochromic regions. The second conductive regions of the first and second electrochromic regions are connected to respective first and second bus bars which are for connection to a low voltage electrical source.

Ultrahigh Density Array of Free-Standing Poly(3-hexylthiophene) Nanotubes on Conducting Substrates via Solution Wetting

Abstract: An ultrahigh density array of vertically and laterally aligned poly(3-hexylthiophene) (P3HT) nanotubes on conducting substrates was successfully fabricated by solution wetting in the anodized aluminum oxide (AAO) template. After solvent annealing, the conductivity of P3HT nanotubes was significantly increased due to highly aligned P3HT chains along the nanotube direction (or perpendicular to the substrate). This approach also provides a facile route for the preparation of ultrahigh density array of various conjugated polymer nanotubes. The conducting polymer nanotube array could be used for high performance organic devices, such as sensors, organic photovoltaic cells, and electrochromic devices.

Remarkable Stability of High Energy Conformers in Self-Assembled Monolayers of a Bistable Electro- and Photoswitchable Overcrowded Alkene

Abstract: Although bistability of molecular switches in solution is well established, achieving highly robust bistable molecular switching in self-assembled monolayers remains a challenge. Such systems are highly attractive as components in organic electronics and molecular-based photo and electrochromic devices. Here we report a remarkably robust surface confined bisthiaxanthylidene redox switch that shows excellent bistability, manifested in reversible changes in spectroscopic and electrochemical properties and in physical properties such as water contact angle changes (ca. 30° difference in water contact angle between the two redox states of a bisthiaxanthylidene self-assembled monolayer). The effect of surface immobilization of bis-thiaxanthylidene on its photochromic, thermal and electrochemical properties is described. Surface immobilization is achieved by incorporating thiol- and alkylsiloxy-terminated “legs” on one of the tricyclic aromatic units. The molecular switch in its neutral and dicationic state, ge...

Electrochromic devices and thin film transistors from a new family of ethylenedioxythiophene based conjugated polymers

Abstract: New electrochromic conjugated polymers and their corresponding devices based on EDOT (ethylenedioxythiophene) are described. The best of these polymers display response times on the order of 1s and high switchable contrast in the visible and near-infrared (Vis-NIR) spectral regions. Thin films (70 nm) of these new polymers displayed optical band gaps on the order of 1.73 eV (7a) < 2.19 eV (7b) < 2.23 eV (7c) < 2.31 eV (4) < 2.34 eV (2) as calculated from their extrapolation of the absorption edges. Polymers 4 and 7a show field effect hole mobilities of ca. 6.7 × 10−5 cm2 V−1s−1 (on/off ratio 104) and 2.5 × 10−5 cm2 V−1s−1 (on/off ratio103), respectively, related to their highly ordered inter-chain packing as confirmed by XRD analyses of polymer 4. Electrochromic characterizations show that polymers 7a–c exhibit significant absorption changes in the infrared at low voltage. The resulting solid-state devices offer promise for electrochromic shutters and filters in the IR, since their high charge transfer mobility and ion injection efficiency permits relatively rapid switching and good switchable contrast, while their robustness exceeds that of aqueous devices.