Optical properties PEDOT

The two electrons transferred from TDAE to PEDOT-PSS are expected to undope the conjugated polymer chains. Since TDAE diffuses into PEDOT-PSS, long exposures to the electron donor induce changes in the optical properties of the polymer film. Optical absorption experiments on 200 nm thick PEDOT-PSS films coated onto a transparent polyethylene terephthalate (PET) substrate. The pol5mier film was exposed to the TDAE vapor in an inert nitrogen atmosphere and shows the difference in absorption spectrum between a film exposed to TDAE and the pristine PEDOT-PSS layer (Figs. 3.10 and 3.11). The modification of the optical properties and the sheet resistance of the pol5mier layer were recorded versus exposure time. The two absorption features at 550 nm and... 

Copol5miers of PEDOT have the electronic and optical properties of PEDOT but can be processed from nonacidic organic solutions. Some commercial materials (TDAE) have good mechanical properties, low acidity, and wet organic substrates without the use of binders or additives. 

Polymer films that combine the optical properties of PEDOT and polypyrrole have been produced by either casting a solution of the PEDOT/PSS suspension followed by electrochemical polymerization of... 

Composites of conducting polymers, e.g., polyaniline and PEDOT, with polyacids, e.g., poly (2-acrylamido-2-methyl-l-methyl-l-propanosulfonic add) (PAMPS), have been shown to be electro-chromic. The polyadd acts as a dopant for the polymer film with the optical properties of the composite being contributed by the conducting polymer. The composites are formed by dther chemical or electrochemical polymerization of the electrochromic component monomer in the presence of the polyacid. Films of polyaniline-PAMPS switch from yellow to green and finally to blue on oxidation [228,229]. Composite films of PEDOT and PAMPS show similar electrochromic properties to PEDOT with the films switching from dark blue in the neutral state to Kght sky blue in the oxidized state [140,230,231]. 

To improve performance, many PEDOT derivatives, used either alone or in combination, have been proposed. Whereas the electro-optical properties of WO3 are fixed, the colors and hues of conducting polymers may be altered by modification of the monomers. Reynolds and co-workers have studied the electrochromic properties of a multitude of EDOT derivatives [82], and recently reported an all-polymer electrochromic device based on two different PEDOT derivatives [187]. Depending on their chemical structure, the various PEDOT derivatives may exhibit different colors upon switching from the oxidized to the reduced state. Furthermore, the contrast ratio is also dependent on the stmcture. For example, polytetradecylethylenedioxythiophene (C14-PEDOT) is similar to PEDOT in switching from transparent to blue, but it has an enhanced optical contrast, and for 2,2-dimethyl-ProDOT an improved contrast ratio combined with a different color - purple instead of blue - is observed [82, 187]. 

The alteration of the optical properties for an electrochromic material involves the insertion or extraction of charge. These polymers can be classified into three types, depending on their specific optical states (1) absorption/transmission-type materials made of metal oxides, viologens or polymers such as PEDOT, including at least one colored and one bleached state for smart windows, (2) display-type materials made of polythiophenes without a transmissive state and (3) materials composed of blends, laminates and copolymers including more than two colored states [7],... 

Kumar and Reynolds also showed that PEDOT can be used as a cathodically coloring polymer in dual polymer electrochromic devices that have both transmissive color-neutral and absorptive highly colored states [74]. Dietrich et al. compared the electrochemical and optical properties of PEDOT and PProDOT [75]. 

Cairns and Crawford applied mechanical and thermal stress on ITO- and PEDOT PSS-coated PET and observed poor mechanical but excellent thermal, electrical and optical properties for ITO on PET. For PEDOT PSS on PET the result was vice versa Good mechanical properties but severe degradation at elevated temperature and inferior electrical and optical properties. ... 

The mosf important concepts to modify fhe optical properties of PEDOT comprise the following ... 

The introduction of bridging groups on the thiophene ring modifies the physical and chemical properties of the polymers obtained. The energy of the optical absorption is reduced in FEDOT, Fig. 9.2(k), and poly(ijothia-naphthalene), (PITN) (Wudl et al., 1984), so that in the conductive state thin films are transparent. PEDOT shows high electrochemical stability in the oxidised state and, when combined with poly(styrenesulphonic acid) counter ions, can be processed from aqueous solution. 

PEDOT, which has reactive methacrylate endgroups, is dispersible in an organic solvent such as nitromethane or propylene carbonate. Films cast from these solutions are smooth and scratch resistant and have good adhesion properties on many substrates. And thin films appear transparent blue with an optical transmittance up to 75 /o.i 4... 

Similarly, introduction of carbazole in 174 also leads to a polymer presenting distinct redox processes and hence optical states [297,298]. Unlike electrochromic materials based on pure PEDOT, these compounds are colored in the oxidized state and colorless in the neutral one. The exploitation of the complementary properties of these two types of polymers has led to electrochromic devices exhibiting a large variety of colors [122],... 

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