Enhancement of Light Harvesting and Photocurrent Generation by ITO Electrodes Modified with meso,meso-Linked Porphyrin Oligomers

ITO electrodes modified with a meso,meso-linked porphyrin oligomer have been prepared for the first time to achieve improved light-harvesting efficiency and a larger quantum yield for photocurrent generation as compared to the corresponding porphyrin monomer system. An increase in the number of the porphyrins in meso,meso-linked porphyrins results in an improvement of the photoenergy conversion efficiency per mol cm -2 in the visible light region as well as a larger quantum yield of photocurrent generation. The relative integrated values of the photocurrents for all of the frequencies in the action spectrum per mol cm -2 in the porphyrin dimer and tetramer systems are determined to be 2.5 and 6.5, respectively, as compared with the values of the porphyrin monomer system.