Electrochromic phenomena in polyaniline films. Effect of pH and influence of the sweep range on cycling lifetimes studied by in situ Raman spectroscopy

Due to fast color changes and easy preparation and use, polyaniline seems to be a promising material for electrochromic devices, as far as long cycling lifetimes can be obtained. A proper coloration was only observed in acidic media. The influence of pH (between 0 and 3) in a HCl+KCl solution was investigated, using Raman spectroscopy. Samples were cycled with various potential ranges and the part played by the anodic reverse potential on the material lifetime was emphasized. The degradation mechanism can be explained by the gradual formation of head-to-head coupling.