Dual-type Electrochromic Devices Research Articles

Synthesis and electrochromic properties of 3,5-diphenyl-2,6-dithiophene-2-yldithieno[3,2-b;2’,3’-d]thiophene

A conducting polymer of 3,5-diphenyl-2,6-dithiophene-2-yl-dithieno[3,2-b;2’,3’-d]thiophene (Thy2Ph2DTT) was synthesized by potentiodynamic method in dichloromethane (DCM)/acetonitrile (AN) (1/1)-NaClO4/LiClO4 (0.1:0.1M) solvent-electrolyte mixture. The resulting polymer was characterized via cyclic voltammetry (CV), Fourier transform infrared (FTIR) and UV-Vis spectroscopy. Its dual type electrochromic device (ECD) with PEDOT was constructed. Spectroelectrochemical and electrochromic properties of the polymer film and the device were investigated in detail. A potential range of 0.0–2.0V was found to be suitable for operating the P(Thy2Ph2DTT)/PEDOT device between red and blue colors. The device displayed good open circuit memory and stability. Properties of Thy2Ph2DTT and P(Thy2Ph2DTT) were compared with 3,5-diphenyldithieno[3,2-b;2’,3’-d]thiophene (Ph2DTT) and its polymer P(Ph2DTT), reported previously, which revealed that introduction of thiophenes to the peripherals of Ph2DTT improved the properties of the corresponding polymer.

Synthesis of a perylenediimide-viologen dyad (PDI-2V) and its electrochromism in a layer-by-layer self-assembled multilayer film with PEDOT:PSS

A new electrochromic molecule, perylenediimide-viologen dyad (PDI-2V), was synthesized and used in the fabrication of layer-by-layer (LBL) self-assembled multilayer films with poly(3,4-ethylenedioxythiophene)–poly(styrenesulfonate) (PEDOT:PSS). Since PDI-2V is a tetracationic organic molecule with high molecular weight, it showed strong electrostatic adhesion to negatively charged PEDOT:PSS. When the electrochromic behaviour of the resulting LBL film was investigated with a single type electrochromic device, the PDI-2V showed a three-stage color change from red to blue to violet under the reduction potential range. A dual type electrochromic device was also fabricated with P3HT spin-coated ITO as a counter electrode. This device exhibited a sharp color change between deep red and dark blue when the applied potential was switched from +2.0 V to −2.0 V.

Dual-type electrochromic device based on polypyrrole and polythiophene derivatives

A dual-type electrochromic device was assembled using optically transparent electrodes modified with thin films of poly[( R)-(-)-3-(1-pyrrolyl)propyl- N-(3,5-dinitrobenzoyl)-α-phenylglycinate], poly(DNBP) and poly(3,4-ethylenedioxy-thiophene), PEDOT and a polymer electrolyte. After assembling, the device was characterized by spectroelectrochemical techniques. The best performance of this device could be obtained by adjusting the relative thickness of the active polymer films and the potential range of operation of the device. The device shows color variation during ca. 350 charge/discharge cycles and can be constructed under atmospheric conditions.

Electrosynthesis of a new polyindole derivative obtained from 5-formylindole and its electrochromic properties

High-quality poly(5-formylindole) (P5FIn) films with conductivity of 2.43 × 10−2 S cm−1 were synthesized electrochemically by direct anodic oxidation of 5-formylindole (5FIn). The electrochemical, thermal, fluorescent and spectroelectrochemical characterizations of this novel polyindole derivative were reported. Fluorescent spectral studies indicate that the P5FIn film with high fluorescence quantum yields and photochemical stability is a novel green-light-emitter. Spectroelectrochemical studies show that P5FIn can change from yellow to green along with the increasing potentials. Furthermore, a dual-type electrochromic device (ECD) based on P5FIn and poly(3,4-ethylenedioxythiophene) (PEDOT) was constructed and its electrochromic properties were investigated. The response time of this device was found to be only 0.9 s and the optical contrast was 56%. The coloration efficiency (CE) was calculated to be 582 cm2C−1. The ECD exhibits a color change from green (neutral) to dark blue (oxidized) with a good open circuit memory and robust cycle life.

A novel conducting polymer based on terthienyl system bearing strong electron-withdrawing substituents and its electrochromic device application

A novel conducting polymer bearing strong electron-withdrawing substituents (EWS) directly attached to the 3,4-positions of the thiophene ring was synthesized by electrochemical polymerization of diethyl 2,5-di(thiophen-2-yl)thiophene-3,4-dicarboxylate (SSS-Diester). The polymer (PSSS-Diester) was characterized by cyclic voltammetry, FT-IR and UV–vis spectroscopy. The polymer has a reversible redox process and demonstrates a stable electrochromic behavior; reddish orange in the neutral state, brown in the intermediate state and green in the oxidized state. Optical density and response time of the dual-type electrochromic device based on PSSS-Diester were found to be 0.23 and 0.6 s at 623 nm, respectively. It is also noteworthy that the device shows good environmental and redox stability (i.e. 94% of the optical activity of the device retained after 500th switch).

Electrochemical polymerization of 9-fluorenecarboxylic acid and its electrochromic device application

Poly(9-fluorenecarboxylic acid) (PFCA) was synthesized by electrochemical oxidation of 9-fluorenecarboxylic acid (FCA) using a mixture of nitromethane and boron trifluoride diethyl etherate as the solvent and tetrabutylammonium tetrafluoroborate as the supporting electrolyte. An insoluble and conducting brownish-orange film was deposited on the electrode surface, both during repetitive cycling and constant potential electrolysis at 1.15 V. Characterization of the polymer film has been carried out using Fourier Transform Infrared spectroscopy technique and thermal behavior was studied via thermal gravimetric analysis. Structural analysis showed that the polymerization of FCA occurred at 2,7-position. Spectroelectrochemical behavior of the polymer film on indium tin oxide working electrode was studied by recording the electronic absorption spectra, in-situ, in monomer-free electrolytic solution at different potentials and it is found that the PFCA film can be reversibly cycled between 0.0 V and 1.2 V. Furthermore, a dual type electrochromic device based on PFCA was constructed and its spectroelectrochemical properties were investigated. The electrochromic device exhibits color change from transparent to dark blue with a good open circuit memory.

The application of triphenylamine-based hole-transporting materials in electrochromic devices

We report the characterization of triphenylamine-based hole-transporting material, N, N′-diphenyl- N, N′-bis(3-methylphenyl)-1, 1′-biphenyl-4,4′-diamine (TPD), used in the electrochromic devices. The electrochromic properties of different TPD thickness were studied by employing the electrochemical and spectroelectrochemical methods. Cyclic voltammograms of TPD films on an indium tin oxide (ITO)-coated glass exhibited one reversible redox couple in the range of 0–1.4 V versus Ag/AgCl in 0.1 N HClO 4. To assemble the dual-type electrochromic devices using different thickness (250, 400, and 1000 nm) of TPD films: ITO/TPD//PU-LiClO 4//PEDOT/ITO, the optical contrast of the devices increases with increasing the TPD film thickness, whereas the 1000 nm TPD film showed relatively excellent stability with respect to the electrochromic characteristics as compared to 250 and 400 nm films; the color of the film changed from orange-brown, transparent, and dark blue at −2.0, 0.0, and +2.0 V (vs. PEDOT), respectively, where PEDOT is poly(3,4-ethylenedioxythiophene)-poly(4-styrenesulfonate).

Fine tuning of color via copolymerization and its electrochromic device application

In this study electrochemical copolymerization of 1-(perfluorophenyl)-2,5-di(thiophen-2-yl)-1H-pyrrole and 3,4-ethylenedioxythiophene was used to fulfill a strategy in achieving desired multichromic properties. The resultant polymer displayed distinct color changes between red–violet, amber, green and blue color with good switching times and optical contrast. A direct correlation between the color of the polymer in neutral state and the applied potential during synthesis was observed. Hence, it was possible to achieve colors from maroon, red–violet, and eggplant to indigo depending on the applied potential. A dual type electrochromic device of the copolymer and poly(3,4-ethylenedioxythiophene) was constructed to evaluate the possible use of such copolymer in device applications. The device displayed multichromism, with 1.1 s switching time and good electrochromic memory.

Electrochromic properties of a soluble conducting polymer: Poly(1-(4-fluorophenyl)-2,5-di(thiophen-2-yl)-1 H-pyrrole)

1-(4-Fluorophenyl)-2,5-di(thiophen-2-yl)-1 H-pyrrole (FPTP) was synthesized and polymerized both chemically and electrochemically. Spectroelectrochemistry experiments reflected a π to π * transition with a band gap energy of 1.94 eV for the polymer. A dual type electrochromic device (ECD) of P(FPTP) and poly(3,4-ethylenedioxythiophene) (PEDOT) was constructed. The device switches between yellow and blue upon application of −0.8 V and +1.1 V, respectively. Optical contrast was calculated as 19.4% whereas switching time was found as 1.4 s at maximum contrast point.

Electrochromic Properties of Copolymer of Terephthalic Acid Bis‐(thiophen‐3‐yl‐methyl) Thioester with Pyrrole

Terephthalic acid bis‐(thiophen‐3‐yl‐methyl) thioester (TTMT) was synthesized via the reaction of thiophen‐3‐yl methanethiol with terephthaloyl dichloride. This 3‐functionalized thiophene monomer was polymerized in the presence of pyrrole (Py) upon constant potential application. Spectroelectrochemistry experiments reflected a π to π* transition with a band gap energy of 2.4 eV for the copolymer. A dual type electrochromic device (ECD) of P(TTMT‐co‐Py) and poly(3,4‐ethylenedioxythiophene) (PEDOT) was constructed. The device switches between greenish yellow and blue upon application of −2.4 V and +0.8 V, respectively. Optical contrast was calculated as 17.5%, whereas switching time was found as 1.6 s at maximum contrast point.

Characteristics of dual-type electrochromic devices based on poly(ethylene oxide) copolymers

Dual-type polymer electrochromic devices based on [(3-thienyl)methylmethacrylate]-co-[p-vinyl benzyloxy poly(ethylene oxide)]/polythiophene and thiophene-capped poly(ethylene oxide)/polythiophene and ethylene dioxythiophene were constructed via electropolymerization. Spectroelectrochemistry, switching ability and stability of the devices were investigated using UV-visible spectrophotometry and cyclic voltammetry. These devices exhibit low switching voltages and short switching times with reasonable switching stability under atmospheric conditions. Copyright © 2006 Society of Chemical Industry

Electrochemical synthesis of poly(3-bromo-4-methoxythiophene) and its device application

Abstract A functionalized thiophene containing both an electron withdrawing and an electron donating group, 3-bromo-4-methoxythiophene (BrMeOTh) was succesfully polymerized in acetonitrile containing 0.1 M tetrabutylammonium tetrafluoroborate (TBABF4) electrolyte via electrochemical oxidation of the corresponding monomer. BrMeOTh exhibits a lower oxidation potential (1.68 V vs Ag/AgCl) than thiophene (2.05 V vs Ag/AgCl). Spectroelectrochemical properties of poly(3-bromo-4-methoxythiophene) (PBrMeOTh) was investigated in situ recording the electronic absorption spectra of the polymer film coated on indium-tin oxide (ITO) at various potentials. The maximum transmittance difference between the oxidized and reduced states was measured as 39.2% and the time required to attain 90% of the total transmittance difference was found to be 1.2 s. Both cyclic voltammetric and spectroelectrochemical studies showed that the polymer exhibit a lower oxidation potential, a relatively narrow band gap, a stable conducting state and a higher degree of electrochemical reversibility. It is also found that, as synthesized PBrMeOTh films possess a linear structure along the polymer backbone. Moreover, dual type electrochromic device of PBrMeOTh with poly(3,4-diethylenedioxythiohene) (PEDOT) was constructed and its spectroelectrochemical, electrochromic switching and open circuit stability were investigated. Dual electrochromic device showed a good optical contrast and distinctive color changes with the ability of good switching times (1.1 s) under atmospheric pressure.

Dual-type electrochromic devices based on both n- and p-dopable poly(dithieno[3,4- b,3′,4′- e]-[1,4]-dithiine)

Polydithieno[3,4- b,3′4′- e]-[1,4]-dithiine (PDTH), being both n- and p-dopable, reveals remarkable color changes as both anodically and cathodically coloring material. In order to investigate its utilization in the electrochromic devices, three different transmissive/absorbtive type polymer electrochromic devices based on both p-type and n-type PDTH were assembled. These are, namely (1) p-type PDTH/poly(3,4-ethylenedioxythiophene) (PEDOT); (2) polythiophene/n-type PDTH; (3) p-type PDTH/n-type PDTH. Spectroelectrochemistry, switching ability, stability and open-circuit memory of the devices were investigated by UV–vis spectrophotometer and cyclic voltammetry. These devices exhibit reasonable switching times and stability under atmospheric conditions.

Single- and dual-type electrochromic devices based on polycarbazole derivative bearing pendent viologen

In relation to electrochromic (EC) device performance, it is important to avoid unwanted power consumption and to minimize electrochemical degradation by using an EC material, which exhibits the desired EC state under no bias voltage in most of the time. Regarding this point, we prepared single- and dual-type EC devices based on poly( N-methyl- N′-(6-carbazole-1-ylhexyl)-4,4′-bipyridinium dihexafluorophosphate) [P(Cz-V)]. Since polycarbazole is oxidative-coloring and viologen is reductive-coloring, the supplementary EC action provides variety in color, which cannot be achieved by individual EC materials. In the single-type device, the polymer became green P(Cz α+-V 2+) at 3 V (versus ITO), bleached P(Cz 0-V 2+) at 0 V, and violet P(Cz 0-V +) at −3 V. In the dual-type device, the complementary action of (Cz α+-V 2+) and P(Cz 0-V +) upon a bias voltage of 3 V showed higher EC contrast compared to the single-type device.

Synthesis, characterization and electrochromic properties of copolymer of 3-{[4-(thien-3-yl-methoxy)phenoxy]methyl}thiophene with thiophene

(3-{[4-(Thien-3-yl-methoxy)phenoxy]methyl}thiophene) (TMPMT) was synthesized via the reaction of 3-bromomethylthiophene with hydroquinone and characterized by nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR). Electrochemical copolymerization of TMPMT with thiophene in acetonitrile/boron trifluoride diethyl etherate (AN/BFEE) solvent mixture was achieved using tetrabutylammonium tetrafluoroborate (TBAFB) as the supporting electrolyte. Resulting copolymer was characterized via cyclic voltammetry (CV), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), four probe technique conductivity measurement and UV–Vis spectroscopy. Spectroelectrochemical analysis of the copolymer [P(TTMT-co-Th)] revealed that π–π ∗ electronic transition occurs at 427 nm with a band gap value of 2.20 eV. Copolymer gives brown color at the fully reduced state whereas; at fully oxidized state the film has a gray-blue color. Kinetic studies were carried out at the maximum contrast wavelength upon measuring the percent transmittance, T% (7.6%) and switching time (2.0 s) to examine the switching ability of the copolymer. Dual type electrochromic device (ECD) of P(TMPMT-co-Th) and poly(3,4-ethylenedioxythiophene) (PEDOT) was constructed. Spectroelectrochemistry, switching ability, open circuit memory and stability of the device were examined by UV–Vis spectroscopy and cyclic voltammetry. The device switches between brown and blue at switching voltages of 0.0 V and 2.8 V with a short switching time of 1.4 s.

Synthesis and Characterization of Thiophen-3-yl Acetic Acid 4-Pyrrol-1-yl Phenyl Ester and its Conducting Polymers

ABSTRACT Thiophen-3-yl acetic acid 4-pyrrol-1-yl phenyl ester (TAPE) monomer was synthesized via reaction of thiophen-3-yl acetyl chloride with 4-pyrrol-1-yl phenol. Homopolymers were achieved by using electrochemical and chemical polymerization techniques. Copolymers of TAPE with bithiophene or pyrrole were synthesized by potentiostatic electrochemical polymerization in acetonitrile-tetrabutylammonium tetrafluoroborate (TBAFB) solvent-electrolyte couple. The chemical structures were confirmed by both Nuclear Magnetic Resonance Spectroscopy (NMR) and Fourier Transform Infrared Spectroscopy (FTIR). Differential Scanning Calorimetry (DSC) and Thermal Gravimetry Analysis (TGA) were used to examine the thermal behavior of the polymers. The morphologies of the films were investigated by Scanning Electron Microscope (SEM). Two-probe technique was used to measure the conductivities of the samples. Moreover, investigations of electrochromic and spectroelectrochemical properties of poly(TAPE-co-BiTh) carried out and the characteristics of dual type electrochromic device based on poly(TAPE-co-BiTh) and poly(3,4-ethylenedioxythiophene) (PEDOT) were reported.

Dual-type electrochromic devices based on conducting copolymers of thiophene-functionalized monomers

Dual polymer electrochromic devices (ECDs) composed of electrochemically deposited conducting copolymers of thiophene-functionalized monomers, 2-[(3-thienylcarbonyl)oxy] ethyl 3-thiophene carboxylate (TOET), 2,3-bis-[(3-thienylcarbonyl)oxy]propyl 3-thiophene carboxylate (TOPT), and 3-[(3-thienylcarbonyl)oxy]-2,2-bis-[(3-thienylcarbonyl)oxy]propyl 3-thiophene carboxylate (TOTPT), and polyethylene dioxythiophene (PEDOT) as the counter part were constructed with tetrabutylammonium tetrafluoroborate (TBAFB) doped gelled poly(methyl methacrylate) (PMMA) and evaluated. An electrochromic device with the following configuration was assembled — indium tin oxide (ITO)-coated glass /conducting copolymer || gel electrolyte || PEDOT/ITO. Spectroelectrochemistry, electrochromic switching, stability and open-circuit memory of the devices were examined.

Characteristics of dual-type electrochromic device based on poly(3-tetradecylthiophene) and poly(3,4-ethylenedioxythiophene)

Two single- and a dual-type electrochromic devices (ECDs) based on poly(3-tetradecylthiophene) (PTDT) and poly(3,4-ethylenedioxythiophene) (PEDOT) with lithium salt in PMMA gel-media were prepared. In the single-type ECDs, red PTDT ( λ max: 494 nm) and blue PEDOT ( λ max: 596 nm) in the reduced states could be switched to their bleached oxidized forms. In the dual-type ECD, the color changed between dark red ( λ max: 502 nm) and dark blue ( λ max: 602 nm) by switching the applied voltage (E(PTDT) versus E(PEDOT)) between −2.2 and 2.2 V. Its electronic absorption was a combination of those of PTDT and PEDOT. Its optical switching rate was much faster than the single-type ECDs. It is presumably because the capacitive charging of each bare ITO electrode in the single-type ECDs partially compensates the applied voltage while in the dual-type ECD, both the electrodes participate in the faradaic reactions. In this dual-type ECD, when one of the electrodes takes part in coloring electrode, the other takes part in complementary electrode leading to fast switching.