A spectroelectrochemical study of the electrodeposition of polythiophene films

Abstract

The growth of polythiophene films has been studied using time resolved in situ transmission spectroscopy in the wavelength range 350–820 nm. Several distinct stages to the polymerisation process have been identified. In the first of these, a small quantity of intermediates, which we suggest might be short chain oligomers, was observed. At slightly longer times, which a previous electrochemically based analysis associated with the expansion of growth sites, the absorbance shifted to longer wavelengths. Finally, features normally considered to be characteristic of the “metallic” form of the polymer predominate. Correlation of spectroscopic and electrochemical data showed these clearly, together with more subtle changes occurring in thicker films which were not apparent from the electrochemical data alone. Absorbance vs. charge plots were used to estimate optical parameters for growing films: whilst we found no evidence for a potential dependence of these parameters in the range 1.80–1.95 V, the values were different from those obtained at high potentials.