Impedance and Electroreflectance of Reduced Poly (3‐Methyl Thiophene)‐P3MT in an Aqueous Electrolyte: Direct Observation of a Polaron Transition

Abstract

We present electrolyte electroreflectance and impedance studies of poly (3‐methyl thiophene) in contact with an aqueous solution of methyl viologen. When the doping level of the polymer is reduced from its "as grown" value a new structure, at 1.7 eV, appears in the electroreflectance spectra which corresponds to the anticipated optical transitions due to the polaron gap states. The polaron spectra are absent in the fully doped and the neutral, "undoped," polymer. The polaron spectra have been monitored as a function of the electrode potential. The electroreflectance results are correlated with impedance measurements and with the photoelectrochemical spectral response of the film as a function of the doping level.