Abstract: After self-assembling a p-aminothiophenol(PATP) monolayer on bare Au electrode, polyaniline(PANI) films were prepared by electropolymerization on the modified Au electrode and three forms of PANI(reduced PANI, partially-oxidized PANI and oxidized PANI) were obtained by electrochemical method. The SEM pattern shows that there are some hills of PANIon a compact layer of PANI. The cyclic votammograms of the probe[K₃Fe(CN)₆/K₄Fe(CN)₆] for the three forms of PANI film show that partially-oxidized PANI has a good electron transport performance. The potential dependence of magnitude and spectra of the photocurrent of PANIfilms were observed. The bandgap energy of 1.45 eV for oxidized PANI, which is the threshold energy of its photocurrent spectra, was obtained. The spectra of photocurrent for partiallyoxidized PANI film shows that it has the characteristics of sub-band gap photocurrent spectra and follows Fowler rule(IPCE^1/2～hν). The bandgap energy of insulating matrix in partially-oxidized PANIis determined as 3.33 eVby the Flowler plots, and the insulating matrix in partially-oxidized PANIis verified to be reduced PANI. The flatband potential, in the order of 0.63 V vs. SCE, is obtained from Mott-Schottky plots. Aphotoelectrochemical process based on internal photoemission in partially-oxidized PANI, which agrees with the model of granular metal island that assumes metallic polymer particles are embedded in the insulating matrix, is proposed.

Key words: Polyaniline, Photoelectrochemistry, Internal photoemission