Structure and photoelectrochemical properties of ITO electrodes modified with self-assembled monolayers of meso, meso-linked porphyrin oligomers

A systematic series of ITO electrodes modified chemically with self-assembled monolayers (SAMs) of meso, meso-linked porphyrin ol igomers have been designed to provide valuable insight into the development of artificial photosynthetic devices. Photoelectrochemical measurements were carried out in an argon-saturated 0.1 M Na₂SO₄ aqueous solution containing methyl viologen (MV²⁺) as an electron acceptor or triethanolamine (TEA) as a sacrificial electron donor in a three electrode system including the modified ITO electrodes. The action spectrum of porphyrin oligomer SAMs exhibits photocurrent generation in a wide wavelength region, demonstrating the enhancement of light-harvesting properties in the visible region. The relative integrated value of the action spectrum as well as the quantum yield of photocurrent generation of the porphyrin oligomer SAMs increases with increasing the number of the porphyrins. These results clearly show that our strategy is highly promising for improving light energy conversion efficiency.