Fabrication of planarly-oriented polycrystalline thin films of smectic liquid crystalline organic semiconductors

Fabrication of planarly-oriented polycrystalline thin films of organic semiconductors was investigated, in which molecules sit parallel, i.e., "face-on" on the substrate so as to allow vertical charge transport favorably through a thin film. With the aid of self-organization of liquid crystalline molecules and an over-coated orientation layer, tens of nm thin films vertically oriented can be re-oriented from "hemeotropic, or vertical" to "homogenous or planar" to achieve polycrystalline thin films planarly oriented after removing the over-coated orientation layer. We investigated the key factors to affect re-orientation of the films and uniformity and surface morphology of the resulting films, including conditions required for the re-orientation and properties of the orientation layer materials and liquid crystals.