Counterion effects on enhancing the electrochromic performance of poly(3,4-ethylenedioxythiophene) thin films

In this study, poly(3,4-ethylenedioxythiophene) (PEDOT), an attractive conducting polymer, was paired up with several counterions, namely perchlorate (ClO4−), nitrate (NO3−), and chloride (Cl−), to improve its electrochromic (EC) properties. Electrochemical polymerization was used to prepare modified PEDOT thin films in aqueous solutions containing 3,4-ethylenedioxythiophene monomer and various counteranions. Among them, Cl−-doped PEDOT (PEDOT-Cl) thin films offered a remarkable EC performance. The PEDOT-Cl thin films prepared in aqueous solutions exhibited multicolor EC properties, unlike the PEDOT thin films prepared in common organic solvents. The PEDOT-Cl thin film achieved a transmittance change of around 30 % in the visible range. The switching times of the PEDOT-Cl thin film were found to be less than 5.0 s, both in bleaching and darkening, for an electroactive area of 4.0 cm2. Moreover, the remarkable electrochromic properties of the PEDOT-Cl thin film were analyzed using different methods.