PHOTOELECTROCHEMICAL PROPERTIES OF POLYANILINE FILMS

The behaviour of electrochemically polymerized polyaniline (PANI) films on platinum and indium tin oxide electrodes has been studied in the dark and under irradiation with low intensity monochromatic UV and visible light. Illumination of the reduced form of PANI under potentiostatic conditions gives rise to small cathodic photocurrents, whereas large cathodic photocurrents are seen under potentiodynamic conditions. The dynamic photoresponse peaks when approximately 10% of the film has been converted to the emeraldine form and then disappears as the film is oxidised further. Photocurrent spectra, recorded under both potentiostatic and potentiodynamic conditions, are similar to the absorption spectrum of the reduced (leucoemeraldine) form of PANI, although they appear to show a red shift when the film thickness is increased. The magnitude of the photocurrents was found to depend linearly on the intensity of the light, and the maximum quantum efficiency was determined to be less than 1%. The leucoemeraldine form of PANI degrades under UV irradiation with a quantum efficiency of about 5 x 10(-4).