Photoelectrochemical Solar Cells: Stabilization of Small Band Gap Semiconductor in Aqueous Solution by Surface-Attached Organic Conducting Polymer

Surface-attached polypyrrole films were shown to produce a marked improvement in the stability of n-type single-crystal and polycrystalline Si against oxidation in an aqueous electrolyte. The current production of n-type polycrystalline Si coated with polypyrrole deteriorated less than 30% during 122 hr of irradiation whereas the unprotected bare electrode stopped producing photocurrent within 30 s. The polymer protection of the n-type single-crystal Si was significantly less than that of the polycrystalline material because of differences in the adhesion of the polymer film to the electrode surfaces. The adhesion strength was shown to depend on various surface properties of Si and other electrode materials. Moreover, the surface morphology of the electrode affected the topography of the growing surface of the polypyrrole film. Requirements are discussed for the applications of organic conducting polymers to photoelectrochemical devices utilized for solar energy conversion.