Photoinduced electron transfer from porphyrin to C-60 in a C-60 vertical bar porphyrin double-layer photoelectrochemical cell

Photoelectrochemical properties of double-layer electrodes consisting of a very thin film of C-60 and porphyrin solids were investigated in a quinhydrone aqueous solution. A larger anodic photocurrent is obtained in the photoelectrochemical cell using an ITO (indium tin oxide)\C-60\Zntpp (5,10,15,20-tetraphenylporphyrinatozinc) electrode compared with that for ITO\C-60 or ITO\Zntpp electrodes. However, when the ITO\Zntpp\C-60 electrode, deposited in reverse order, is employed, a cathodic photocurrent is obtained. Neither of the double-layer electrodes exhibits rectification. The results suggest that the primary process of the photocurrent generation is a photoinduced electron transfer from Zntpp to C-60 enhancing the photocurrent, and that the Zntpp and C-60 solids do not act as semiconductors but as photosensitizers. (C) 1997 Elsevier Science S.A.