A novel photoelectrochromic device with dual application based on poly(3,4-alkylenedioxythiophene) thin film and an organic dye

A novel photoelectrochromic device (PECD) with dual application was studied using an electrochromic polymer thin film, poly(3,3-diethyl-3.4-dihydro-2H-thieno-[3,4-b][1,4]dioxepine) (PProDot-Et-2), and an organic photosensitive dye, FL dye 1, which was adsorbed on a TiO2 electrode. In the presence of the redox couple, the electron transfer reaction at the electrolyte/PProDot-Et-2 conducting polymer interface was found to determine the electrochromism of the PECD. The rate constants of the electron transfer (k(0)) for different redox couples at the PProDot-Et-2 film were obtained by using electrochemical impedance spectroscopy (EIS) and were correlated with the coloration depth of the thin film. Since I-/I-3(-) and Br-/Br(3)(-)couples possess the highest and the lowest k(0) value, respectively, the PECD was investigated using these two redox couples under constant light illumination of 50 mWcm(-2). The I-/I-3(-) couple provided a higher short circuit current density (I-sc) when acting as a dye-sensitized solar cell (DSSC), thus the switching response upon coloration (ca. 3 s) was much faster than that of the PECD using the Br-/Br-3(-) couple (ca. 2 min). On the contrary, the PECD using Br-/Br-3(-) exhibited a larger transmittance attenuation of ca. 33.7%, in comparison to that using I-/I-3(-) (ca. 14.1%). (C) 2008 Elsevier B.V. All rights reserved.