Results 1 - 10 of 568
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[en] Pristine tetraaniline and three carboxyl-substituted tetraaniline derivatives, that is, tetraaniline ((Ani)4), carboxyl-capped tetraaniline ((Ani)4-COOH), amino/carboxyl-capped tetraaniline (NH2-(Ani)4-COOH) and carboxyl-capped star-shaped tetraaniline (Tri-(Ani)4-COOH) were synthesized, and the influence of substituent and molecular architecture on their electrochromic properties was investigated. Pristine (Ani)4 shows lowest electrochromic properties while the carboxyl-capped star-shaped Tri-(Ani)4-COOH possesses the best electrochromic properties with fast bleaching and coloring times of 2.04 s and 1.90 s, respectively, promising optical contrast of 74.2%, and improved coloration efficiency of 133.31 cm2C−1 at 750 nm. This enhanced electrochromic performance can be attributed to the introduction of carboxyl substituent and star-shaped molecular architecture, which are able to improve the interchain charge movement, electron movement between films and substrate and enhanced ion diffusion resulting from loosely packed molecular structure of films, and confirmed by cyclic voltammetry and atomic force microscope results, implying the introduction of special substituent and molecular architecture is an effective strategy to improve the electrochromic properties of aniline oligomers.
[en] Electrochromic (EC) smart pixel display was designed and fabricated using a novel monomer di-4-isopropyl benzyl substituted (3, 4-propylene dioxythiophene) (ProDOT-IPBz2). The polymer thin film showed absorption between 450 and 650 nm at a fully reduced state. The absorption peak narrowed down slightly towards longer wavelength region (850–900 nm) at the oxidation states. Siju et al has reported the coloration efficiency (CE) of the thin film as ∼305 cm2C−1. The ProDot-IPBZ2 thin film was used to fabricate EC pixel display of 2 × 2 pixel array on a patterned ITO coated glass. The optical color contrast of the EC pixel display is 40% at 600 nm, with a switching time of about 2 s and 2.5 s respectively. The CE of EC pixel was found to be 555 cm2C−1 at 600 nm in the fully doped state. This EC pixel switched for more than 1000 cycles with good color contrast (<5% T). EC pixel displays showed transmissive, magenta and violet colored states at applied potentials of 1.5, −1.0 and −2.0 V respectively. This EC pixel display is efficient with faster response time and better color contrast. (paper)
[en] Highlights: • A polyoxometalate has been incorporated into a polymer. • An electrochromic behavior has been evidenced. • An hybrid organic/inorganic film has been prepared with PVK. • Electrochromism has been characterized by spectroelectrochemistry.
[en] Research highlights: → In this paper we demonstrate several ways of tuning the doping front migration process in polymer electronic multilayer structures for the first time. By altering the migration layer thickness the migration velocity may be controlled and it is possible to switch between migration mechanisms. The mechanism of delamination produces rapid jumps in migration velocity, while the addition of 2-hydroxyethylcellulose (HEC) can inhibit this effect. In case of vapor activation the migration velocity may be influenced by the relative humidity or by varying the concentration of hygroscopic salts added to the migration layer. The migration mechanisms can be explained in terms of diffusion, capillary transport, and delamination. Tuning the migration process may be used to construct polymer electronic structures such as enhancement and depletion type pseudo transistors and electrical switches (ON-OFF and OFF-ON) with an improved switching time of several minutes. The doping front width is determined by microscopic optical absorption spectroscopy and can be controlled by the concentration of the doping solution. In case of low concentrations the electrochromic effect of the double front is observed. - Abstract: We demonstrate several methods of modifying the doping front migration process in multilayer structures, enabling control of migration velocity and switching between different migration mechanisms. Sharp jumps in migration velocity may be induced using a delamination effect. The influence of migration layer thickness and composition is examined. Migration velocity may also be influenced by exposing the system to a defined relative humidity or by varying the concentration of a hygroscopic salt in the migration layer. The migration mechanisms can be explained in terms of diffusion, capillary transport, and delamination. By tailoring the migration process a variety of polymer electronic structures such as pseudo transistors (enhancement and depletion type) and electrical switches (ON-OFF and OFF-ON) may be fabricated. Further examinations about the doping front width are given and the phenomenon of a double front is described.
[en] Using a three-dimensional finite volume model, the thermal performance of an electrochromic vacuum glazing was simulated for insolation intensities between 0 and 1200 W m-2. The electrochromic evacuated glazing simulated consisted of three glass panes 0.5 m by 0.5 m with a 0.12 mm wide evacuated space between two 4 mm thick panes supported by 0.32 mm diameter pillars spaced on a 25 mm square grid contiguously sealed by a 6 mm wide metal edge seal. The third glass pane on which the electrochromic layer was deposited was assumed to be sealed to the evacuated glass unit. The simulations indicate that when facing the indoor environment, the temperature of the glass pane with the electrochromic layer can reach 129.5 deg. C for an incident insolation of 600 W m-2. At such temperatures unacceptable occupant comfort would ensue and the durability of the electrochromic glazing would be compromised. The glass pane with the electrochromic layer must therefore face the outdoor environment
[en] Highlights: • Pyridinium-salt-based electrochromic materials, TPCBDs, were designed and synthesized. • TPCBDs exhibit dual-colored and fast electrochromic switching properties. • N-substituents significantly influence their electrochromic properties. - Abstract: This work reports novel dual-colored and fast switching electrochromic materials based on pyridinium salts, 1,1′,1″,1‴-tetrakis(4,4′,4″,4‴-tetrapyridyl)cyclobutane derivatives (TPCBDs). TPCBDs show outstanding electrochromic properties including fast electrochromic switching, dual color, reasonable contrast, low driving voltage, and good stability. TPCBDs are promising candidates for visible electrochromic displays because of their remarkable electrochromic behaviors.
[en] Kelvin probe force microscopy (KPFM) adapts an atomic force microscope to measure electric potential on surfaces at nanometer length scales. Here we demonstrate that Heterodyne-KPFM enables scan rates of several frames per minute in air, and concurrently maintains spatial resolution and voltage sensitivity comparable to frequency-modulation KPFM, the current spatial resolution standard. Two common classes of topography-coupled artifacts are shown to be avoidable with H-KPFM. A second implementation of H-KPFM is also introduced, in which the voltage signal is amplified by the first cantilever resonance for enhanced sensitivity. The enhanced temporal resolution of H-KPFM can enable the imaging of many dynamic processes, such as such as electrochromic switching, phase transitions, and device degredation (battery, solar, etc), which take place over seconds to minutes and involve changes in electric potential at nanometer lengths. (paper)
[en] Recent developments in consumer electronics, e.g. smartphones, tablet PCs or compact cameras, demand the development of very compact, active, optical microsystems. Because of their low power consumption, low operation voltage and cheap fabrication, voltage-controlled electrochromic devices (ECDs) based on polymer materials are promising candidates. However, the broad application of ECDs is still hindered by crucial technological obstacles. In this paper, we address two main issues: the structuring of the electrochromic material (ECM) and its underlying transparent conductive electrode on a microscale and additionally, the assembly of the ECD as an electrochemical cell with the challenges of airtight sealing, appropriate chemical stability, electrical insulation and the necessity of defining a compartment to hold the liquid electrolyte inside the cell. We first introduce a technological sequence consisting of batch processes (UV lithography and dry and wet etching) to render the microscale structuring of the ECM possible. Furthermore, we exploit the outstanding properties of the thick film dry photoresist Ordyl SY 300 to complete the assembly of ECDs with single-layer technology. As a proof of principle, we present the first results of an ECD device based on a poly(3,4-ethylenedioxythiophene) (PEDOT) material that works as an aperture stop with three coaxial segments, each individually controlled by an external voltage. (paper)