Photocathode Kinetics of Phthalocyanine/Fullerene with Respect to the Base Electrode for the Bilayer Coating

概要

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The photocathodic characteristic of an organic bilayer of metal-free phthalocyanine (H2Pc; p-type semiconductor) and fullerene (C60; n-type semiconductor) was investigated with different kinds of base electrode employed (i.e., indium–tin oxide (ITO), and Au), particularly in terms of electron transfer kinetics. The kinetics of the H2Pc/C60 photocathode soaked in the water phase was found to be dominated by the reduction reaction taking place at the C60/water interface. Therefore, an analysis of the kinetics was performed by assuming an adsorption step prior to the rate-limiting electron transfer step, for which the Langmuir adsorption equilibrium was considered, and the resulting analysis equations were applied to photocurrents dependent on the concentration of Fe3+ (electron acceptor). Kinetic analysis revealed the magnitude of the rate-limiting reduction to be independent of the kind of base electrode used. This also showed that the photoelectrode kinetics cannot be affected by photophysical processes (e.g., carrier generation, recombination, and transport) in the p/n interior as well as by electron injection from the base electrode to H2Pc, which differs explicitly from the corresponding solar cell (in the dry state).
2009-02-25