Similarity between optical response kinetics of conducting polymer thin film based gas sensors and electrochromic devices

Abstract

Chemically deposited polyaniline (PANI) thin films were used as optically active materials in optochemical gas sensors (OGS) as well as in electrochromic devices (ECDs). An electrochemically deposited poly(3-methylthiophene) (P3MT) thin film based ECD was also prepared to be compared to PANI based ECDs. In all these optical devices, the optical response kinetic curves of PANI and P3MT films can be fitted quite well with two terms of the same exponential expression: one faster and one slower. The faster one could be attributed to a rapid specific surface or interface reaction process, and the slower one to a volumetric or bulk diffusion-reaction process. The physical meanings of the fitting parameters come from the Langmuir adsorption theory and Freundlich isotherm in the case of OGS and the Butler-Volmer equation for polymer based ECDs.