Evaluation of photoanodic output on carbon cluster/phthalocyanine films with respect to the types of n-type conductors employed

Organic p/n bilayers, composed of carbon cluster (i.e., C₆₀ or C₇₀, n-type semiconductor) and zinc phthalocyanine (denoted as ZnPc, p-type semiconductor) were prepared and used as photoelectrodes in the water phase. The bilayer (i.e., C₆₀/ZnPc or C₇₀/ZnPc) coated on a base electrode showed photoanodic characteristics in the presence of thiol, which induced the oxidation of thiol at the ZnPc/water interface along with the photophysical events (i.e., visible-light absorption, carrier generation, and its conduction) in the p/n interior. Kinetic analysis was conducted for both systems, which revealed that the overall photoelectrode reactions are kinetically dominated by the charge transfer between ZnPc and thiol. Considering the result of a reference system (i.e., a photoanode of perylene derivative/ZnPc bilayer), the photoelectrode characteristics involving the rate-limiting oxidation are discussed with respect to the types of n-type conductors.