• E S R Gopal

      Articles written in Bulletin of Materials Science

    • Comparison of performance parameters of poly(3,4 ethylenedioxythiophene) (PEDOT) based electrochromic device on glass with and without counter electrode

      S Sindhu K Narasimha Rao E S R Gopal

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      Conjugated polymers are promising materials for electrochromic device technology. Aqueous dispersions of poly(3,4-ethylenedioxythiophene)-(PEDOT) were spin coated onto transparent conducting oxide (TCO) coated glass substrates. A seven-layer electrochromic device was fabricated with the following configuration: glass/transparent conducting oxide (TCO)/PEDOT (main electrochromic layer)/gel electrolyte/prussian blue (counter electrode)/TCO/glass. The device fabricated with counter electrode (Prussian blue) showed a contrast of 18% and without counter electrode showed visible contrast of 5% at 632 nm at a voltage of 1.9 V. The comparison of the device is done in terms of the colouration efficiency of the devices with and without counter electrode.

    • Optical, electrochemical and morphological investigations of poly (3,4-propylenedioxythiophene)–sultone (PProDOT–S) thin films

      S Sindhu C R Siju S K Sharma K N Rao E S R Gopal

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      In this paper, we have carried out thin film characterization of poly(3,4-propylenedioxythiophene)–sultone (PProDOT–S), a derivative of electrochromic poly(3,4-propylenedioxythiophene) (PProDOT). PProDOT–S was deposited onto transparent conducting oxide coated glass substrates by solution casting method. Single wavelength spectrophotometry is used to monitor the switching speed and contrast ratio at maximum wavelength (𝜆max). The percentage transmittance at the 𝜆max of the neutral polymer is monitored as a function of time when the polymer film is repeatedly switched. This experiment gives a quantitative measure of the speed with which a film is able to switch between the two states i.e. the coloured and the bleached states. PProDOT–S films were switched at a voltage of 1.9 V with a switching speed of 2 s at 𝜆max of 565 nm and showed a contrast of ∼37%. Cyclic voltammetry performed at different scan rates have shown the characteristic anodic and cathodic peaks. The structural investigations of PProDOT–S films by IR spectra were in good agreement with previously reported results. Raman spectra of PProDOT–S showed a strong Raman peak at 1509 cm-1 and a weak peak at 1410 cm-1 due to the C = C asymmetric and symmetric stretching vibrations of thiophene rings. The morphological investigations carried out by using scanning electron microscope (SEM) of polymer films have shown that these polymers are found to be arranged in dense packed clusters with non-uniform distribution having an average width and length of 95 nm and 160 nm, respectively.

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