Electrochemical synthesis of poly (3-octylthiophene) in a room temperature ionic liquid and its application in an electrochromic device

Poly(3-octylthiophene) (POcT) was electrochemically synthesized via galvanostat method by using ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate, [BMIM]PF₆) as the growth medium and the supporting electrolyte. The thin film of POcT was orange yellow in its fully reduced state. After oxidization of the undoped polymer, the film underwent a reversible change to the dark blue form. Spectroelectrochemical analysis of POcT at various doping levels confirm the bipolaron band structure and a starting φ-φ* interband transition around 1.94 eV. Moreover, a POcT film based electrochromic device (ECD) was constructed and its electrochromic properties were also investigated in this paper.