Photosensitized electron injection from an ITO electrode to trichromophoredyes deposited on Langmuir-Blodgett films

Two novel trichromophore amphiphilic dyes 1-methyl-2,4,6-tris[2-(3'-methoxy -4'-(octadecycloxy)phenyl)- ethenyl]pyridinium iodide (MTMS) and 1-methyl-2 ,4,6-tris[2-(4'-(octadecyloxy)phenyl)ethenyl]pyridnium iodide (MTOS) have b een synthesized and successfully transferred on semiconducting transparent indium-tin oxide (ITO) electrodes by a Langmuir-Blodgett (LB) technique. Th e observed photocurrent strongly depends on the applied electrode potential , the presence of O-2, the concentrations of methyl viologen (MV2+) and hyd roquinone (H(2)Q), and the pH of the electrolyte. Action spectra of the pho tocurrent generation are coincident with the absorption spectra of the LB f ilm-modified ITO electrode, indicating that the dyes aggregated in the LB f ilm are responsible for the photocurrent. Under favorable conditions the qu antum yield are as high as 1.40% and 1.54% for the monolayer films of MTMS and MTOS, respectively. Models for the mechanism of photocurrent generation under different conditions are proposed.