Electropolymerization electrochromic devices

For graphene/CP composite films, the goal of combining the materials has been both to obtain a mechanically more robust material and to combine the attractive properties of the individual components to obtain a superior material. As discussed above, graphene/CP composite materials can be S3mthesized by a range of different methods. In this section, electropolymerization of graphene/CP composite electrode materials and the direct use of such electrodes in the field of supercapacitors and electrochromic devices will be briefly summarized. 

Differendy linked carbazole derivatives possessing selenophene and pyrene (the latter not covered in this review) moieties were electropoly-merized (14EA430). The electropolymerized polymers displayed unusual properties upon electrochemical doping suggesting their potential use as electroactive layers in electrochromic devices. A typical synthesis of 2,7-diselenophenylcarbazole is shown below. 

Ferraris and colleagues studied laminate films of PEDOTT spin coated on electropolymerized N-methylpolypyrrole, polyaniline spin coated on PEDOT PSS, and polyaniline deposited on electropolymerized N-methylpolypyr-role. The films were analyzed using CIE (x, i/)-chromaticity coordinates. The observed colors in their fully doped and reduced states were found to be linearly dependent on the color coordinates of the two individual polymers of the laminate, which allows for adjusting the observed color by variation of layer thickness of an electrochromic device in a viable and predictable way. Inganas ° studied a laminate structure made from polypyrrole electro-chemically deposited on top of a PEDOTPSS layer formed by spin coating. In contrast to Ferraris et al. he found that the spectra of the laminate electrode matches well with spectra of pure polypyrrole. 

While an invaluable tool in producing conjugated polymers on conducting substrates, electropolymerization has limitations that include a lack of primary structure verification and characterization along with the inability to synthesize large quantities of processable polymer. To overcome the insolubility of PEDOT, a water-soluble polyelectrolyte, poly(styrenesulfonate) (PSS) was incorporated as the counterion in the doped PEDOT to yield the commercially available PEDOT/PSS (Baytron P) (39), which forms a dispersion in aqueous solutions [140]. While this polymer finds most of its application as a conductor for antistatic films, solid state capacitors, and organic electronic devices, its electrochromism is distinct and should not be ignored. 

Many organic substances show electrochromism and can serve as ion storage layers in devices with W oxide films. Snch a device was reported by Yoshida et al. specifically it incorporated sputter-deposited W oxide, electropolymerized polyaniline, and an electrolyte of LiC104 + PC. Transmittance changes between 80 and 4% could be obtained with time constants of 10 s. The cycling dnrabihty was 5 x 10 times. 

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