Electrochromic properties of polypyrrole composite films in solid polymer electrolyte

Polypyrrole (PPy)–poly(ether urethane) (PEU) and PPy–poly(ethylene-co-vinyl alcohol) (EVOH) composite films were prepared by the electrochemical polymerization of pyrrole on LiClO4-containing PEU and EVOH films coated on indium–tin oxide (ITO), respectively. The electrochromic device composed of ITO-coated glass/PPy–PEU (or PPy–EVOH) composite film/LiClO4-containing PEU (as a solid polymer electrolyte)/ITO-coated glass was fabricated and the electrochromic properties were characterized. As a result, the device using PPy–PEU composite film showed a larger difference of transmittance (ΔT) at 800 nm between the doped and undoped states, and a shorter response time than the device using PPy–EVOH film. On the contrary, the latter device had a longer cycle lifetime under the repeated application of pulsed voltage (±3 V, 1 Hz). These electrochromic behaviors were discussed in connection with the properties of the used matrix polymers.