Enhanced diffraction efficiency in a photorefractive liquid crystal cell with poly(9-vinylcarbazole)-infiltrated mesoporous TiO2 layers

The photorefractive effect of a layer-structured liquid crystal cell was significantly enhanced when a C-60-doped poly(9-vinylcarbazole) (PVK)/TiO2 nanocomposite was used in two photoconductive layers. The C-60-doped PVK/TiO2 nanocomposite film was prepared by infiltrating C-60-doped PVK into a highly ordered mesoporous TiO2 layer. The addition of the TiO2 layer to the C-60-doped PVK layer increased the first-order Raman-Nath diffraction efficiency from 24% to 42.9%. This enhancement of diffraction efficiency is attributed to a blocking effect of charge recombination in the composite layer. The electron transfer from the PVK layer into the TiO2 layer would decrease the recombination of photogenerated charges in the PVK layer, while charges in the PVK layer could participate in the formation of a space-charge field.