Structure and polyphenylvinylene concentration effect on the photoconductivity response from mesostructured silica films

Highly ordered thin films were made by a dip-coating technique. Sodium dodecyl sulfate (SDS)-templated sol-gel films posses lamellar structure, and cetyltrimethylammonium bromide-templated sol-gel films exhibit a hexagonal structure. In this work, mesostructured films made with these surfactants were doped with polyphenylvinylene (PPV). X-ray diffraction patterns indicate that the films have the known structure. The photoconductivity technique was used to determine the charge-transport mechanism on these films. The parameters for the photovoltaic effect (φl₀) and photoconductivity (φμτ) were determined from the current density versus the applied-electrical-field results. Lamellar films have bigger values of these parameters than the corresponding ones from the hexagonal films, and the conductivity is better in the former. Charge-transport parameters are quite high in the PPV-doped samples compared with the reported values in films doped with Disperse Red 1 and carbazole (SiK). KNbO₃:Fe^3- photorefractive crystals are less photoconductive and photovoltaic than the PPV films, too. There is a critical polymer concentration in the SDS samples.