Electrochromic properties of 3-arylthieno[3,2-b]thiophenes Dedicated to the memory of Prof. Ayhan S. Demir of Middle East Technical University, Ankara, Turkey.

3-Phenylthieno[3,2-b]thiophene, 3-(4-methoxyphenyl)thieno[3,2-b]thiophene and 3-(4-N,N-dimethylaminophenyl)thieno[3,2-b]thiophene were electropolymerized on ITO by applying constant potentials of 1.7, 1.65, and 1.4 V, which had light transparent reddish yellow, brown and brownish yellow colors, respectively. Their electrochromic devices (ECD) were fabricated with PEDOT on ITO coated glass electrodes. Spectroelectrochemical and electrochromic properties of the devices were investigated in detail. A potential range of 0.0-1.6 V was found to be suitable for operating the devices between pinkish orange and transparent light blue colors. The maximum transmittance difference (%ΔT) of the ECDs were measured to be 4.5, 7 and 3% and the time required to reach 95% of transmittance difference were 2, 1.85, and 1.8 s. They demonstrated good optical memory both in oxidized (with only transmittance changes of 1.5, 1, and 2.5%) and reduced states (with almost no transmittance change).