Photoelectric response from a stilbazolium dye in a Langmuir–Blodgett film-modified SnO2 electrode

Abstract

Cathodic photocurrent generation from a stilbazolium dye [(CH₃)₂NC₆H₄—CHCH—C₅H₄NC₁₈H₃₇I (SI)] in a Langmuir–Blodgett (LB) film-modified SnO₂ electrode has been investigated. The action spectrum coincides very well with the absorption spectrum of the SI–SnO₂ electrode, indicating that the SI aggregates in the LB film are responsible for the photocurrent. Factors such as the intensity of the irradiation, concentration of donor or acceptor in the electrolyte solution, bias voltage, pH and degree of saturation with O₂ or N₂, have been studied. The results indicate that the electrons flow from the electrode through the LB film to the electrolyte solution (1 mol dm^–3 KCl). It is found that tautomerization of SI takes place in ethanol solvent under irradiation. The quantum yield is very small, but can be improved by adding acid to the solution. A possible mechanism of the tautomerization of SI and of the photocurrent generation has been proposed.