Urbach tail analysis on the defect states of polypyrrole thin films prepared by AC plasma polymerization Urbach tail analysis on the defect states of polypyrrole thin films prepared by AC plasma polymerization

Abstract

AbstractPolypyrrole is a widely studied conducting polymer with excellent optical and electrical properties. Polypyrrole thin films in the pristine and iodine doped forms have been prepared by ac plasma polymerization. The in situ doping of iodine during the process of plasma polymerization modified the optical absorption behaviour of the thin films due to the incorporation of charged defects in the film structure. Optical band gap and related constants are estimated from optical absorption studies. The Urbach tail analysis of the pristine and doped thin films shows that more defect levels are created, when the polymerization was carried out in the iodine atmosphere. The electrical properties of these thin films were estimated from the conductivity measurements. It is found that in the case of iodine doped films, the optical band gap decreased and electrical conductivity enhanced when compared to the pristine ones. The results are correlated with the structural differences of the pristine and doped thin films with the help of Fourier Transform Infrared Spectroscopy (FTIR) analysis.