Multifunctional Molecular Material Combining Photocurrent Generation and Second-Order Optical Nonlinearity in LB Monolayer Films

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Multifunctional Molecular Material Combining Photocurrent Generation and Second-Order Optical Nonlinearity in LB Monolayer Films

A novel amphiphilic stilbazolium dye, (E)‐N‐methyl‐4‐[2‐(4‐N‐methyl‐N‐hexadecylaminophenyl) ethenyl]‐2‐isoquinolinium iodide (MHIQ), was synthesized. The dye was successfully transferred onto ITO electrode or quartz by the Langmuir‐Blodgett (LB) technique. The second harmonic generation (SHG) and photocurrent generation properties of the LB film transferred under 35 mN/m of surface pressure were investigated. The broad absorption maximum of the LB monolayer of MHIQ at 434 nm is far away from the wavelength (532 nm) of resonant enhancement effect, and its second harmonic susceptibility x⁽²⁾ is 167 pm/V, which means that the isoquinolinium is a good electron‐accepting group. The photocurrent generation experiment shows that the photocurrent generation properties are dependent on the experimental conditions including bias voltage, redox couples and light intensity. By a light irradiation at 440 nm, the photocurrent generation quantum yields of the dye LB monolayer are 0.50% in 0.5 mol/L KG electrolyte solution and 17.5% in 0.1 mol/L KI electrolyte solution with 0.01 mol/L I₂, respectively, indicating that the dye MHIQ is a good photoelectric conversion material.