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 H 2 and O 2 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 2 Pc, a p-type semiconductor) and fullerene (C 60, an n-type semiconductor) was applied to a photocathode in the water phase, H 2 was evolved at Pt-coated C 60 along with the conduction of the electron carriers photogenerated at the p/n interface, concurrently yielding O 2 at the counter electrode. This is the first example of C 60 participation in H 2 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.