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

Abstract

A novel photoelectrochromic device (PECD) with dual application was studied using an electrochromic polymer thin film, poly(3,3-diethyl-3,4-dihydro-2 H-thieno-[3,4- b][1,4]dioxepine) (PProDot-Et 2), and an organic photosensitive dye, FL dye1, which was adsorbed on a TiO 2 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 mW cm −2. The I −/I 3 − couple provided a higher short circuit current density ( J 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%).