Electrochromic Polymer Films Research Articles

Electrosynthesis of redox-active and electrochromic polymer films from triphenylamine-cored star-shaped molecules end-capped with arylamine groups

Four starburst molecules with a triphenylamine (TPA) core through the amide group linked to the terminal triphenylamine or (N-phenyl)carbazole (NPC) unit, coded as T-3(NHCO-TPA), T-3(NHCO-NPC), T-3(CONH-TPA), and T-3(CONH-NPC), were synthesized and their electrochemistry and electropolymerization were investigated. The oxidation potential and the stability of the oxidized forms of the starbursts are affected by the orientation of amide linkage and the structure of terminal triarylamine unit. Robust polymeric films could be built onto ITO/glass surface by repetitive cyclic voltammetry (CV) of the T-3(NHCO-TPA) solution containing an electrolyte. The electrodeposited films exhibited reversible electrochemical processes and strong color changes upon electro-oxidation, which can be switched by potential modulation. The electrochromic behavior of the film was clearly interpreted on the basis of spectroelectrochemical studies. T-3(CONH-TPA) did not undergo electropolymerization effectively. T-3(CONH-NPC) also could electrochemically polymerize to polymer films upon repeated CV scans. However, their electrochromic switching stability is less than that of the polymer film from T-3(NHCO-TPA).

Coronene Diimide Containing Redox Active Electrochromic Polymer Film via Electropolymerization of Diphenylamine End Groups

A new monomer containing coronene diimide with diphenylamine end groups (DCTD) has been synthesized and polymer thin films were electropolymerized onto gold, glassy carbon and ITO electrode surfaces. The resulting polymers show a reversible 2e− oxidation of the diphenylbenzidine unit and reversible reductions of the aromatic diimide. AFM was used to characterize the polymer film morphology. The electronic and electrochromic properties of these films were evaluated for use in organic electronic applications.

Electrochemical and electrochromic properties of diketopyrrolopyrrole-based conjugated polymer

We demonstrate novel high-performance electrochromic polymer (LGC-D148) films which contain a diketopyrrolopyrrole (DPP) as the acceptor and thiophene with 2,5-difluorophenylene-dithiophene as the donor. The polymer films undergo highly reversible and long-term stable electrochemical reactions and exhibit distinctive redox peaks. In situ optical measurements reveal that the LGC-D148 films have green/transparent electrochromism with a fast switching speed and a coloration efficiency of >900cm2/C.

Electrochromic properties of phenantrene centered EDOT polymers

A series of phenantrene centered donor-acceptor type electroactive 3,4-ethlenedioxythiophene (EDOT) monomers (EP-X) containing N, S and Se heteroatom on the bezophenantra-X-diazole acceptor unit have been synthesized by Stille coupling reaction. These monomers were electrochemically polymerized by potentiodynamic method to obtain electrochromic polymer films. Spectro-electrochemical properties were also investigated by UV-vis absorption connected with the cyclic voltammetry measurements. The polymer films exhibited a remarkable trend of visible color (yellow, orange, red) at the neutral state due to changing the central acceptor moiety. These polymer films have multielectrochromic properties by means of moderately changing the absorbance/transmittance at the visible regime upon applied positive potentials. The donor-acceptor interaction at the neutral state correlated by DFT calculations was also supported by the interesting trend in the colors of these polymers. Finally, the electrochromic performance of EP-X polymer films represented a high redox stability, reasonable contrast ratio, coloration efficiency and response times.

Investigation of P3HT electrochromic polymer films prepared by ultrasonication of polymer solutions

This paper describes the enhancement in stability and electrochromic properties of regioregular poly(3-hexylthiophene) (rrP3HT) polymer films in ambient conditions via ultrasonication of the polymer solution before deposition. The ultrasonicated polymer solution was spin coated onto an ITO substrate, and the electrochromic properties of the resulting rrP3HT films were characterized by UV–Vis spectroscopy, cyclic voltammetry and spectroelectrochemistry. The morphology and crystallinity of the polymer films were measured by atomic force microscopy and X-ray diffraction. Ultrasonication of the polymer solution controlled and increased the intra-chain interaction of the resulting polymer film on an ITO substrate. This method resulted in the polymer film changing colors at a voltage 0.2 V less than an untreated film with concurrent high stability and a fast response switching time of 1–2 s. This method was demonstrated to be a convenient way to lower the applied voltage and to increase the stability of the electrochromic rrP3HT film.

Conductive PEDOT:PSS Electrodes in Electrochromic Devices

We present new electrochemical device designs made entirely of electrically conducting polymer electrodes to reversibly switch a magenta colored poly(3,4-propylenedioxy-thiophene) (PProDOT) electrochromic polymer (ECP) film. Thin conductive PEDOT:PSS films have been incorporated as conductive transparent electrodes in solution processable absorptive/transmissive (window type) electrochromic devices making it available for high-throughput processing on a wide range of substrates. Different (in)organic acid and polar solvent post-treatments have been used to tune the conductivity of the blade coated PEDOT:PSS electrodes. We reached a conductivity up to 2000 S cm-1 on different substrates, enough to reversibly switch our ECP film between -1 V and 1 V. We will demonstrate how the structural design, construction, charge-balancing, electrode conductivity and the electrochemical properties of the PProDOT have an influence on the device performance quantified by its contrast, switching speed, bending capabilities and long-term switching stability. We combine our device design with a fundamental study of the electrochemical processes occurring at both electrodes. Using these new designs, we have developed an all-polymer solution processed electrochromic device approaching the characteristics of a device made using inorganic transparent conducting electrodes, e.g. indium tin oxide (ITO), with the added advantage of using flexible and rough substrates. Figure 1

Electrochromism and Nonvolatile Memory Device Derived from Triphenylamine-Based Polyimides with Pendant Viologen Units.

Three novel solution-processable polyimides containing triphenylamine and pendant viologen moieties are prepared from the newly synthesized diamine and three commercially available dianhydrides. The thermally stable polyimide with strong donor-acceptor charge-transfer possesses write-once read-many-times memory behavior with excellent operation stability. The obtained multicolored electrochromic polymer films reveal ambipolar electrochemical behavior with high optical transmittance contrast of coloration changed from transmissive neutral state to the cyan/magenta/yellow redox states, implying great potential for application in smart window and displays.

Highly Optical Performance Photoelectrochromic Device Based on Br−/Br3− Electrolyte

A highly optical performance photoelectrochromic device (PECD) is assembled and investigated. The device consists of an electrochromic (EC) polymer film, a ruthenium-based dye-sensitized TiO2 electrode and a layer of Br−/Br3− electrolyte. The optical modulation of device is 44.3% at 582nm, which is much higher than device based on commonly used I−/I3− electrolyte. Its switching times between colored and bleached states are fast under illumination (100mWcm−2), 2.5s for coloring process and 2.6s for bleaching process. Also, this PECD reveals a robust cyclic durability of photoelectrochromic performance over 1000 cycles. These may indicate that Br−/Br3− electrolyte is beneficial for collaboration of photovoltaic and electrochromic parts. The results not only provide a method to assemble high performance PECD, but also disclose its potential for commercialization.

Performance and reliability of cellulose acetate-based gel electrolyte for electrochromic devices

This work describes optimized conditions for the use of cellulose acetate (CA), a naturally derived polymer, in gel electrolytes (GEs) for electrochromic devices (ECDs). The GEs were doped with lithium perchlorate (LiClO4) as a supporting salt electrolyte and propylene carbonate as a solvent. The conductivity of GEs with varying CA concentration was evaluated by a conductivity meter to determine the effectiveness of electrolyte ion transport in the GE matrix. Then, we employed poly(3-hexylthiophene-2,5-diyl) (P3HT) thin films as an electrochromic layer on an ITO substrate. The P3HT film served as the main cathodic electrochromic layer, the GE as an ion conducting layer, and a piece of bare ITO substrate as an anodic electrochromic layer. We evaluated the stability of the P3HT film by measuring the optical and electrochemical properties of P3HT thin films on ITO in GEs through UV–Vis and cyclic voltammograms obtained during application of potential to the films. Current/voltage data and related performance for ECDs were investigated. The results showed that the prepared GEs have high stability within the operative potential window for ECDs. The electrochromic polymer films operated with the prepared GE showed good stability with fully reversible color change for more than 1000 cycles without polymer film or GE degradation. This work shows the first example of the use of GE with a natural polymer matrix in electrochromic devices and demonstrates their reliability under repetitive switching of applied voltage for up to 1000 cycles.

Black-to-transmissive electrochromic switching polymer films via solution co-processing

Two newly synthesized electrochromic polymers were utilized to prepare black films, which exhibited moderate optical contrast and robust stability.

Electrosynthesis of ambipolar electrochromic polymer films from anthraquinone–triarylamine hybrids

ABSTRACTTwo ester derivatives featuring anthraquinone as an interior core and terminal electroactive triphenylamine or carbazole groups were prepared by the condensation of 2,6‐dihydroxyanthraquinone with 4‐(diphenylamino)benzoyl chloride and 4‐(9H‐carbazol‐9‐yl)benzoyl chloride, respectively. The electrochemistry and electropolymerization of these monomers were investigated. The polymeric films were built onto ITO/glass surface by repetitive cyclic voltammetry scanning of the monomer solutions containing an electrolyte. The electrogenerated polymer films exhibited reversible electrochemical processes and strong color changes upon electro‐oxidation or electro‐reduction, which can be switched by potential modulation. The remarkable electrochromic behavior of the film was clearly interpreted on the basis of spectroelectrochemical studies, and the electrochromic stability was evaluated by the electrochromic switching studies. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 644–655

Modification of ITO Surface for High Performance of Electrochromic Polymer Film

Modification of ITO Surface for High Performance of Electrochromic Polymer Film

Comparative Study of Electrochromic Enhancement of Latent Fingerprints with Existing Development Techniques*

To address the challenge of capturing latent fingerprint evidence from metal surfaces, a new method of latent fingerprint enhancement based on electrochromic polymer films has recently been developed. Here, we present a study comparing the development and visualization of nonvisible fingerprints on stainless steel substrates using this electrochromic enhancement approach with three classical methods (dusting, wet powder, and cyanoacrylate fuming). Two variants of the electrochromic enhancement method were utilized with polyaniline and poly(3,4-ethylenedioxythiophene) as the electrochromic materials. Fingerprint samples were taken from different donors (varying in age and gender) and were exposed to different environments for systematically varied periods of time (up to 28 days). The environments represent plausible evidential scenarios: left under ambient conditions, washed with aqueous soap solution, washed with acetone, submerged in water, and maintained at elevated temperature. The electrochromic enhancement procedure frequently outperformed the traditional methods, particularly for samples exposed to more challenging histories.

High Contrast and Dynamic Electrochromic Display with Thin Solid Hyper-Branched Polymer Film

A new hyperbranched electrochromic (EC) polymer containing many viologen units was developed. The EC polymer film was easily fabricated by a spin coating method and employed as thin EC display film. All-solid EC display was constructed with polymeric electrolyte gel and hyperbranched polymer. The EC display was operated with good contrast and rapid response at low bias voltage, 2.5 V.

Electrochemical Modulation of Color and Fluorescence in One Cell Using Conducting Polymers

A modulation of electrochromic and electrofluorescent properties in one device was possible by coupling of 9-methylanthracene polymer (PMAn) having blue light emission under 390 nm light excitation, and poly(3,4-ethylenedioxythiophene) (PEDOT) having blue to transparent electrochromism (EC). The different redox states between electrofluorescent (EF) and electrochromic (EC) polymer films could provide the electrochemically switchable color and fluorescence in one device. Alternative EF and EC switching between a blue light/dark and colorless/blue color was achieved from the device with reversible switching within 3.5 s by the potential application under ±2 V.

A new donor–acceptor carbazole derivative: Electrochemical polymerization and photo-induced charge transfer properties

A new donor–acceptor carbazole derivative containing N-2-(2-ethylhexyl)-1,8-napthalimide as acceptor pendant was synthesized at three steps and directly coated on to ITO glass surface by using electrochemical process. Subsequently, electrochemical co-polymerization of this monomer was carried out by using 3,4-ethylenedioxythiophene (EDOT) as co-monomer to give electrochromic polymer film. Spectro-electrochemical studies indicated that co-polymer films exhibit relatively lower band gap than that of homo-polymer. Consequently, photo-induced energy and charge transfer properties from the donor-carbazole to naphthalimide-acceptor were studied by using cyclic voltammetry, UV–vis absorption and emission spectroscopy.

Black to Transmissive Switching in a Pseudo Three-Electrode Electrochromic Device

We introduce the first π-conjugated polymer-based, black-to-transmissive and multicolored switching electrochromic device (ECD) constructed in a Pseudo 3-Electrode Electrochromic Device (P3-ECD) architecture. In this ECD, the non-electrochromic, yet electroactive, polymer poly(3,4-propylenedioxypyrrole-N-propionitrile) (PProDOP-N-EtCN) serves as a counter electrode material. This transmissive polymer helps eliminate the contrast limitations seen in dual polymer ECDs that use combinations of anodically and cathodically coloring polymers. The P3-ECD adds colors by transmitting light through two independently controlled working electrodes (coated with two different electrochromic polymer films) and two counter electrodes (coated with PProDOP-N-EtCN) stacked together with a gel electrolyte. The two cathodically coloring EC polymers that were used in this work are, a diester-substituted poly(3,4-propylenedioxythiophene) (PProDOT-(CH2CO2C12H25)2) for the first one, namely PProDOT-ester, and a donor−acceptor ana...

Electropolymerization and ion sensitivity of chemiluminescent thienyl systems

Abstract Redox driven chemiluminescent (CL) compounds based on thienyl and pyridazine systems, namely 2,3-dihydrothieno(3,4-d)pyridazine-1,4-dione (T-Lum) and 5,7-di-thiophen-2-yl-2,3-dihydro-thieno[3,4-d]pyridazine-1,4-dione (TTT-Lum), were synthesized. Soluble compounds both in organic media and basic aqueous solution were found to give CL and electroluminescent (EL) reactions by the treatment of oxidants (H 2 O 2 and KMnO 4 ) and by an external potential pulse on the working electrode, respectively. Furthermore, the CL reaction can be speeded up by Fe 3+ ion or blood samples. On the other hand, one of the compounds, TTT-Lum, can be polymerized successfully via electrochemically both in 0.1 M LiClO 4 /acetonitrile containing 5% of borontrifluoro diethylether (BF 3 -Et 2 O) and neat BF 3 -Et 2 O solution. The corresponding polymer film (PTTT-Lum) bearing CL units has a very stable and a well-defined reversible redox couple. Also, the electrochromic polymer film has a band gap of 1.74 eV and exhibits EL behavior.

Visualizing the Electric Field in Electrolytes Using Electrochromism from a Conjugated Polymer

Electrochromic polymer films, employed as display elements, smart windows, and the base material for electrochemical electronic devices, can be addressed solely through ionic transport via an elect ...

Switchable window based on electrochromic polymers

A large contrast ratio (>ΔΤ = 60%) and rapid switching (0.3–1 s) electrochromic (EC) polymer device that consists of a laminated two-layer structure between two electrodes was prepared. The new design consists of an indium tin oxide (ITO) glass electrode, a cathodic EC polymer film, a solid electrolyte, and a counterelectrode that replaces the anodic EC polymer and ITO electrode. Four EC polymers including two new EC polymers, Poly[3-methyl-3′-propyl-3,4-dihydro-2H-thieno(3,4-b)(1,4)dioxepine] (PProDOT-MePro) and Poly[3,3-diethyl-3,4-dihydro-2H,7H-(1,4)dioxepino(2,3-c)pyrrole] (PProDOP-Et2), were synthesized as cathodic EC polymers. A carbon-based counterelectrode was prepared for comparison with an Au-based counterelectrode. Several kinds of polymer gel electrolytes were prepared for comparison. The devices (windows) were increased in area from 0.028 × 0.04 in.2, 1 × 1 in.2 to 3 × 3 in.2 Three main components, the EC polymer film, the gel electrolyte, and the counterelectrode, were studied and their optical properties, conductivities, and repeatabilities were compared. The effects of window size on the contrast ratio, switching speed, power usage, and repeatability were studied.