Electrochromism

About: Electrochromism is a research topic. Over the lifetime, 13097 publications have been published within this topic receiving 294637 citations.

Variable transmittance electrochromic devices

Abstract: Single-compartment, self-erasing, solution-phase electrochromic devices, solutions of electrochromic compounds for use as media of variable transmittance in such devices, and electrochromic compounds for such solutions are provided. The devices of the invention are surprisingly stable to cycling between light and dark states, have continuously variable transmittance to light as a function of electrical potential applied across the solution in a device, and have transmittance that can be varied over more than a factor of 10, from clear to dark or from dark to clear, in several seconds. Thus, the devices are especially suitable as variable transmittance components of variable transmission light filters, including windows, and variable reflectance mirrors, including anti-glare rearview mirrors in automobiles. Also provided are improved variable reflectance mirrors, wherein transmittance of reflected light is varied by thermochromic, photochromic or electro-optic means and wherein the reduction in transmittance which is required to eliminate perceptible reflection of an object to the eyes of an observer is reduced by disposing the plane of the highly reflective surface of the mirror at an angle with respect to the plane of the surface through which light from the object enters the mirror.

Perfluoroalkanoate‐Substituted PEDOT for Electrochromic Device Applications

Abstract: The recent emergence of organic electrochromics on both the scientific and industrial levels has expedited the synthesis of new materials with varied electrochemical and optical properties. The structural versatility and broad usage of poly(3,4-ethylenedioxythiophene) (PEDOT) has stimulated many research groups to focus on the potential of PEDOT derivatives. Here we report the first synthesis of pentadecafluoro-octanoic acid 2,3-dihydro-thieno(3,4-b)(1,4)dioxin-2-ylmethylester (EDOT-F), along with its electrochemical polymerization, characterization, and incorporation into electrochromic devices (ECDs). PEDOT-F is a cathodically coloring polymer that exhibits sub-second switching time between a dark-blue neutral state and a transmissive sky-blue oxidized state, and expresses a 63 % change for both transmittance at λmax and colorimetrically determined luminance. Hexafluorophosphate-doped free-standing films of PEDOT-F possess conductivities of up to 65 S cm–1. Variable transmittance ECDs constructed with PEDOT-F and poly[3,6-bis(2-(3,4-ethylenedioxythienyl))-N-methylcarbazole] (PBEDOT-NMeCz) exhibit an optical contrast of 60 % at λmax (580 nm) and an overall luminance change of 60 %. Indicating the hydrophobicity of this polymer, doped PEDOT-F exhibits a water contact angle of 110°, significantly higher than the 30° exhibited for the doped PEDOT parent.

Na2SO4-assisted synthesis of hexagonal-phase WO3 nanosheet assemblies with applicable electrochromic and adsorption properties

Abstract: For the first time, a mesoporous hexagonal-phase Na0.17WO3.085·0.29H2O nanosheet/microflower hierarchical structure has been synthesized employing a one-pot hydrothermal process with the assistance of Na2SO4. It is shown that Na2SO4 not only acts as a stabilizer to facilitate the generation of a metastable hexagonal phase, but also function as a structure directing agent to assist the construction of nanosheet assemblies. The formation mechanisms have been rationalized. The materials have been thoroughly characterized by XRD/BET/FESEM/EDX/TEM/TGA. This hexagonal-phase Na0.17WO3.085·0.29H2O nanosheet/microflower hierarchical structure exhibits applicable electrochromic and adsorptive properties due to its unique crystallographic configuration and microstructures, promising its application in energy-saving smart windows and wastewater treatment.

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.