Molecular hydrogen evolution by organic p/n bilayer film of phthalocyanine/fullerene in the entire visible-light energy region

This article presents a novel approach to photochemical energy conversion by employing organic compounds. We demonstrated that water can be photoelectrochemically split into H₂ and O₂ using an organic photodevice responsive to the entire visible-light energy range of <750 nm. When an organic p/n bilayer of metal-free phthalocyanine (H ₂Pc, a p-type semiconductor) and fullerene (C₆₀, an n-type semiconductor) was applied to a photocathode in the water phase, H₂ was evolved at Pt-coated C₆₀ along with the conduction of the electron carriers photogenerated at the p/n interface, concurrently yielding O₂ at the counter electrode. This is the first example of C ₆₀ participation in H₂ evolution: a mechanism was proposed, involving the formation of an active species (i.e., C ₆₀^2-) on the basis of the results of in situ spectroelectrochemical measurements.