Enhancement of Second Harmonic Generation and Photocurrent Generation of a Novel Stilbazolium Dye Dimer in Langmuir−Blodgett Monolayer Films

Abstract

A novel amphiphilic stilbazolium dye dimer, bis{[1-(N-methyl-4-pyridinium)-2-(4-N-methyl-N-hexadecylaminophenyl)]ethenyl}methanediiodide (C1BP) was synthesized, and (E)-N-methyl-4-[2-(4-N-methyl-N-hexadecylaminophenyl)ethenyl]pyridinium iodide (C1P) as a standard for comparison was also synthesized. They were successfully transferred onto the semiconducting transparent indium−tin oxide (ITO) or quartz as H-aggregates by the Langmuir−Blodgett (LB) technique. This centrosymmetric dimer (C1BP) can exhibit strong second-harmonic generation (SHG) by the LB method. The second harmonic susceptibility χ(2) of the monolayer film reaches 167 pm V-1 for C1BP and that for C1P is 125 pm V-1. The photoelectrochemistry of these dyes monolayer films was investigated in a traditional three-electrode cell. Steady cathodic photocurrent is obtained upon excitation of the dyes in LB films deposited on an ITO electrode. The observed photocurrent generation quantum yield strongly depended on the applied electrode potential, con...