Photoelecric Conversion by A/S/D LB Films

Abstract

A novel electrochemical photodiode was fabricated by depositing complex LB films which consist of an electron acceptor (A), a sensitizer (S), and an electron donor (D) amphiphile. In these amphipathic molecules, a viologen moiety acts as an A unit, a pyrene or a porphyrin moiety as an S unit and a ferrocene moiety as a D unit, respectively. By arranging these three units on a gold optically semitransparent electrode (AuOTE) regularly in space normal to the electrode surface, e. g. (A)/(S)/(D) or (D)/(S)/(A), the photoinitiated vectorial flow of electrons could be achieved and was detected as photocurrents in a photoelectrochemical cell. Not only three-layer systems, but also the stack of the multilayers of each components, e. g. in the form of [A][A][A]/[S][S][S][S]/[D][D][D] and [D][D][D]/[S][S][S][S]/[A][A][A] were examined. The photocurrent in the latter systems was high er than that in the former systems. The photocurrent had o pposite directions depending upon the spatial arrangement of [A], [S] and [D] units in the film and was in accordance with the energy level profile a cross the film.