Reactions at the two sides of an ECD device studied by Raman spectroscopy

An all solid-state electrochromic device (ECD) using polyaniline (PANI)for anodic coloration and tungstic acid WO3, 2 H2O for cathodic coloration,sepa rated by a polymer electrolyte (PAMPS) presents very good performances. To check the sequences of the protonation/deprotonation and oxidation /reducti on reactions arising in the two optically active materials, Raman spectrosc opy was used on the two sides of the ECD. An improvement of the PANI crysta lline order due to the interfacing with PAMPS, especially using PANI doped with camphorsulfonic acid (PANI-CSA) is observed, which is one of the: reas ons of the excellent performances of the device. The free electrons injecti on in the device, which is the key of their good reversibility, is ensured at high potentials by the cathodic tungsten bronze, and at moderate potenti als by the anodic leucoemeraldine salt.