Photoelectrical properties of Langmuir-Blodgett films of poly (methyl phenylsilane)s

Langmuir-Blodgett (LB) films were prepared from poly(methylphenylsilane) bearing electron acceptor π-conjugated substituents. The small limiting area (0.078 nm2) per one repeating unit of polysilane (PSi) in monomolecular film and the large thickness of the film (6 nm) suggest that the polymer chains are not fully spread on water surface. The electrical and photoelectrical properties of Al/LB film/Au sandwich cells containing various numbers of the polysilane layers were studied. Holes were transported from the Al electrode through the LB film to the Au electrode from when the light was absorbed by the polysilane. The highest photovoltaic effect occurred in the first monolayer of polysilane at the Al contact. The cell resistivity and the photovoltage were decreased by parallel conductance of defects in the films consisting of small numbers of PSi layers.