Dual Polymer Electrochromic Devices Research Articles

Highly Conductive and Solution-Processable n-Doped Transparent Organic Conductor

Transparent conductors (TCs) play a vital role in displays, solar cells, and emerging printed electronics. Here, we report a solution-processable n-doped organic conductor from copper-catalyzed cascade reactions in the air, which involves oxidative polymerization and reductive doping in one pot. The formed polymer ink is shelf-stable over 20 days and can endure storage temperatures from -20 to 65 °C. The optimized n-doped thin-film TC exhibits a low sheet resistance of 45 Ω/sq and a high transmittance (T550 > 80%), which can rival indium tin oxide. The transparent organic conductor exhibits excellent durability under accelerated weathering tests (85 °C/85% RH). Furthermore, the n-doped polymer film can also function as an electrode material with a high volumetric capacity. When it is paired with p-doped PEDOT:PSS, a record-high coloration efficiency is obtained in a dual-polymer electrochromic device.

New dual conjugated polymer electrochromic device with remarkable yellow-to-green switch for adaptive camouflage

Electrochromic devices that reversibly switch between yellow and green have great potential in adaptive camouflage. However, such device with excellent performances for practical applications is scarce. Herein, we fabricated a new dual conjugated polymer electrochromic device based on two self-synthesized conjugated electrochromic polymers P1 and P2 that possess excellent yellow-to-transmissive and green-to-transmissive electrochromism, respectively. Following straightforward color complementation principle of dual polymer electrochromic device, the resulted electrochromic device achieved reversible color changes between yellow and green, and showed good overall performance, including low driving voltages (≤0.6 V), rapid switching speed (≤2.0 s), high color difference (ΔE*ab = 60.6), and lasting cyclic stability (>12,000 cycles). In the end, patterned prototype devices based on the design of dual conjugated polymer device have been successfully assembled, demonstrated the potential application in adaptive camouflage. This work is an important step towards enabling enhanced capabilities for electrochromic camouflage.

Electrosynthesis and characterization of an electrochromic material containing biscarbazole–oxadiazole units and its application in an electrochromic device

Electroactive poly(2,5-Bis(9-methyl-9 H-carbazol-3-yl)-1,3,4-oxadiazole) (PolyBCO) film was synthesized to form a highly stable conducting polymer with excellent electrochromic properties. The polymer was characterized by cyclic voltammetry, UV–Vis-NIR spectroscopy and colorimetry. Spectroelectrochemistry analysis demonstrated that the polymer can undergo both p-type and n-type doping processes. The polymer has four accessible color states. Further kinetic studies demonstrated that the polymer revealed high contrast ratio (75%), fast response time (0.9s), excellent stability and color persistence. A dual-polymer electrochromic device was constructed in sandwich configuration where PolyBCO was used as the anodically coloring material. The device switches between a transmissive light gray state and a blue-colored state with a fast response time and high stability.

A Dual‐Polymer Electrochromic Device with High Coloration Efficiency and Fast Response Time: Poly(3,4‐(1,4‐butylene‐(2‐ene)dioxy)thiophene)–Polyaniline ECD

A new dual-polymer electrochromic device (ECD) composed of poly(3,4-(1,4-butylene-(2-ene)dioxy)thiophene) (PBueDOT) and polyaniline (PANI) with a hydrophobic molten salt electrolyte has been developed. To build this system, an alkylenedioxy ring in the BueDOT backbone was expanded to include a strongly electron-donating alkylenedioxy bridge, and the thickness and surface morphology of the corresponding PBueDOT film were controlled systematically. Not only the dual-electrochromic-polymer-electrode system, but also the expanded alkylenedioxy ring in the BueDOT backbone, synergistically improved the electrochromic performance. From the coloration efficiency (CE) value calculations, we found that the CE was enhanced up to 930 cm(2) C(-1). Furthermore, these ECDs showed an extremely fast response time of less than 80 ms.

Dual n- and p-Type Dopable Electrochromic Devices Employing Transparent Carbon Nanotube Electrodes

We report on the use of highly transmissive single-walled carbon nanotube (SWNT) films as electrodes in electrochromic devices that employ a dual n- and p-type dopable donor−acceptor polymer, poly[5,8-bis-(3-dihydro-thieno[3,4-b][1,4]dioxin-5-yl)-2,3-diphenyl-pyrido[3,4-b]pyrazine], or poly(bisEDOT-PyrPyr-Hx2). This low bandgap polymer is capable of repeated, stable electrochemical cycling between a neutral form and both an oxidized, p-doped state and a reduced, n-doped state. The ability of this electrochromic material to exhibit a stable n-type doped state enabled the construction of an absorptive/transmissive dual-window electrochromic device showing optical changes over a broad energy range—from the mid-infrared to the visible region. This absorptive/transmissive dual polymer electrochromic device is unique in that it exhibits electrochromism utilizing the same polymer as both the cathodically and anodically coloring material. Infrared electrochromic behavior was achieved with the use of SWNT films du...

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...

Fabricating red–blue-switching dual polymer electrochromic devices using room temperature ionic liquid

In this work, room temperature ionic liquid (RTIL)—1-butyl-3-methyl-imidazolium hexafluorophosphate ([BMIM]PF 6)—was employed to fabricate dual polymer electrochromic devices (DPECDs). [BMIM]PF 6 was used as the electrolyte both in the electrochemical synthesis of conducting polymers (CPs) and in the fabrication of DPECDs. The electrochemically deposited poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(3-methylthiophene) (PMeT) were employed to serve as two complementary coloring electrochromic thin films. Through combining these two electrochromic layers, the assembled DPECDs were found to switch between deep red and deep blue, which are two primary colors for a display. By employing RTIL as electrolyte, the devices retained 65% of their optical contrast and electroactivity after 5×10 3 deep double potential steps, showing enhanced stability and durability. The DPECDs also exhibited stable electrochromic performance, with a maximum optical contrast of 26% at 665 nm, and achieved a high coloring efficiency of 460 cm 2 C –1.

The role of water in the synthesis and performance of vapour phase polymerised PEDOT electrochromic devices

Parameters affecting the quality of vapour phase polymerised (VPP) PEDOT and their influence on electrochromic device performance were investigated. Specifically, the role of water during synthesis was examined and a polymerisation mechanism proposed. Paradoxically, water vapour is essential for PEDOT polymerisation, however, too high a loading leads to crystallite formation in the oxidant layer, rendering the oxidant inactive. Changes in water vapour affect the doping level of the polymer, presumably due to poor conjugation along the polymer's backbone during synthesis. The addition of a surfactant, PPG-ran-PEG, was studied using XPS. The surfactant inhibited oxidant crystal growth and slowed the rate of PEDOT polymerisation, reducing film defects and improving PEDOT conductivity. Controlling and optimising the levels of water vapour and surfactant during synthesis resulted in reproducible, high conductivity, high optical switch, PEDOT films. Finally, complementary dual-polymer electrochromic devices utilising (pre- and post-process-enhanced) VPP PEDOT and PMAS (control) were fabricated and changes in switching transmission evaluated.

A bis-selenophene substituted alkoxy benzene derivative as a highly stable novel electrochromic polymer

Up to date there are few studies reporting the use of selenophene derivatives as electrochromic polymers. This report highlights the synthesis of a selenophene containing multi-ring aromatic polymer which possesses reasonable optical contrasts at both visible and near-IR regions. Electrochemical synthesis of a conducting polymer from a multi-ring aromatic monomer, 2-(2,5-bis(hexyloxy)-4-(selenophen-2-yl)phenyl)selenophene (BSB(OC 6H 13) 2), was achieved at a lower potential than its corresponding parent, selenophene. The strong absorption band for the undoped polymer was 474 nm and the onset energy for the π–π * transition (Eg) was 1.9 eV (645 nm). A novel dual-polymer electrochromic device was constructed in sandwich configuration where poly(BSB(OC 6H 13) 2) was used as the anodically coloring material. It is the first electrochromic device where a selenophene-containing polymer was used as an active layer. The device switches between a rose-colored state and a blue-colored state with a fast response time (less than 1 s).

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.

In Situ Colorimetric Analysis of Electrochromic Polymers and Devices

We report a colorimetric method for the in situ study of electrochromic polymers based on the CIE system of colorimetry. This method is useful for the comparison of the electrochemical and optical properties of conjugated polymers, and for gaining control of the color of dual polymer electrochromic devices. Twelve electrochromic polymers were investigated using in situ colorimetric analysis in order to define their CIE coordinates and electrochemical potential windows. By controlling the electron density and steric interactions along conjugated polymer backbones, we have developed a set of electrochromic polymers that provides colors throughout the full range of color space. The applicability of the method is illustrated with a model dual polymer device based on poly(2-(3,4-ethylenedioxy)thienyl(biphenyl)) (PBEDOT-BP) and poly(3,6-bis(3,4-ethylenedioxy)thienyl)-N-methylcarbazole) (PBEDOT-NMeCz). This device yields green/brown colors (L* = 48, a* = 0, b* = 20 and L* = 44, a* = 6, b* = 26) interesting for e...

High Contrast Ratio and Fast-Switching Dual Polymer Electrochromic Devices

A series of dual polymer electrochromic devices (ECDs) based on 12 complementary pairs of conducting polymer films have been constructed using 3,4-ethylenedioxythiophene-containing conducting polymers. Poly[3,6-bis(2-(3,4-ethylenedioxythiophene))-N-methylcarbazole] (PBEDOT-NCH3Cz), poly[3,6-bis(2-(3,4-ethylenedioxythiophene))-N-eicosylcarbazole] (PBEDOT-NC20H41Cz), and poly[4,4‘-bis(2-(3,4-ethylenedioxythiophene))biphenyl] (PBEDOT-BP) were utilized as anodically coloring polymers that electrochemically switch between an oxidized deep blue absorptive state and a transmissive (orange or yellow) reduced state. Poly(3,4-ethylenedioxythiophene) (PEDOT) and its alkyl derivatives (PEDOT-C14H29 and PEDOT-C16H33) have been used as high-contrast cathodically coloring polymers that switch between a deep blue absorptive state in the reduced form and a sky blue, highly transmissive state in the oxidized form. The dual polymer ECDs were constructed by separating complementary pairs of EC polymer films, deposited on ITO glass, with a gel electrolyte composed of a lithium salt and plasticized poly(methyl methacrylate) (PMMA). Device contrast ratios, measured as Δ%T, ranged from 27% to 63%, and subsecond switching times for full color change were achieved. These devices were found to exhibit extremely high coloration efficiencies of up to 1400 cm2/C over narrow (ca. 100 nm) wavelength ranges and to retain up to 60% of their optical response after 10 000 deep, double potential steps, rendering them useful for EC applications.

Unique variable-gap polyheterocycles for high-contrast dual polymer electrochromic devices

We have carried out studies on an extensive series of electron rich monomers which oxidatively polymerize at low potentials. Alkyl derivatized poly(3,4-ethylenedioxythiophenes) (PEDOT's) exhibit a high degree of visible light transparency in the oxidized state, while being an opaque blue in the reduced state. These polymers can be switched rapidly (sub-second) between states with high optical contrasts of up to 60% AT. Multi-ring monomers have been prepared using EDOT moieties as terminal polymerizable un'rts, to yield the most easily oxidized thiophene based monomers reported to date, which efficiently electropolymerize. Polymers have been prepared with electronic band gaps that range from a relatively low 1.4 eV up to 2.5 eV. The inclusion of transition metal ions, electronically coupled to the conjugated backbone, allows further tuning of the polymer's redox properties. These polymers behave as complementary electrochromic materials and have been employed in dual polymer electrochromic devices. Judicious choice of proper cathodically and anodically coloring polymers yield devices which exhibit high optical contrasts (>50% T), multi-color capabilities, long term switching stability (>10 4 deep switches), and rapid switching characteristics with 25% optical contrast observed with 100 mS switches.

Electrochromic and Redox Electroactive Polymers Based on Ethylenedioxythiophene Derivatives

ABSTRACTA family of electrically conductive polymers based on 3,4-ethylenedioxythiophene (EDOT) and its derivatives will be discussed as electrochromic and redox electroactive materials. Poly(alkylethylenedioxythiophenes), derivatized with octyl and tetradecyl pendant chains, exhibit significantly faster redox switching characteristics than the unsubstituted parent polymer. Bis(2-(3,4-ethylenedioxy)thienyl)arylene (BEDOT-Ar) and vinylene monomers electropolymerize at low potentials avoiding degradative side reactions. We outline the properties of EDOT polymers which exhibit low band gaps allowing for the formation of conductive complexes with a high degree of visible light transmission and show their electrochromic properties. The BEDOT-vinylene polymer, for example, has a band gap of 1.4 eV. A relatively high degree of electrochromic contrast is found at 600 nm as the polymers switch between insulating deep purple absorptive and conductive light blue states. Solid-state dual polymer electrochromic devices have been constructed using a combination of complementary anodically and cathodically coloring polymers based on the EDOT core.