Enhancement of photocurrent generation of two novel stilbazolium dye dimers in LB monolayer films

Abstract

Novel amphiphilic stilbazolium dye dimers, bis{[1-(N-methylpyridinium-4-yl)-2-(3-methoxy-4-octadecyloxyphenyl)]ethenyl}methane diiodide (BPOM) and bis{[1-(N-methylpyridinium-4-yl)-2-(4-octadecyloxyphenyl)]ethenyl}methane diiodide (BPO) were synthesized, and they were successfully transferred onto semiconducting transparent indium–tin oxide (ITO) as H-aggregates by Langmuir–Blodgett (LB) techniques. The photocurrent generation properties of monolayer films of these dyes were investigated in a traditional three-electrode cell. A steady cathodic photocurrent was obtained upon excitation of the dye LB monolayer films deposited on an ITO electrode. The observed photocurrent generation quantum yield strongly depended on the applied electrode potential, concentration of the redox couples in the electrolyte solution, and the chemical structure of the dye congeners. The dye monomers, (E)-N-methyl-4-[2-(3-methoxy-4-octadecyloxyphenyl)ethenyl]pyridinium iodide (POM) and (E)-N-methyl-4-[2-(4-octadecyloxyphenyl)ethenyl]pyridinium iodide (PO) as the standards for comparison were also studied. Data show that the photocurrent generation quantum yields are 0.35% and 0.26% for BPOM and BPO, respectively, while those for POM and PO are 0.19% and 0.11%, respectively. From the photoelectrochemical measurement, the enhanced photocurrent generation properties in the dimer compared with those in the corresponding monomer were observed.