Electrochemical Properties of Electrochemically Polymerized Polypyrrole Film in the Dark and under Light Irradiation

Polypyrrole films prepared on Pt or SnO2 through electrochemical oxidative polymerization of pyrrole were characterized with respect to electroconductivity by photoelectrochemical measurements. Redox reactions of solution species such as methyl viologen, hydroquinone, oxygen, Cu2+, I−, and Br− occur on these electroconductive films. Light excitation of the film with wavelengths shorter than 550 nm results in observable cathodic photocurrent at the potential region more negative than 0.0 V vs. Ag. The polypyrrole film is a p-type semiconductor with a bandgap energy of ca. 2.2 eV and is stable during redox reactions.