Modulating Three-Dimensional Molecular Orientation of Liquid Crystal Semiconductor by Anisotropic Surface Treatment

We present a method to achieve three-dimensional (3D) molecular alignment control of a liquid crystal organic semiconductor (LC-OSC) leveraging the long-range order of liquid crystalline properties. For this purpose, a specially designed LC-OSC molecule, MeOPh-BTBT-C8, exhibiting a fluidic nematic (N) phase crucial for large-area alignment and a smectic E (SmE) phase with enhanced molecular order, was designed. Alignment was manipulated by flipping a sandwich cell comprising the LC-OSC layer between two substrates with uniaxial–planar degenerate alignment and crossed rubbing directions, responding to surface anchoring and temperature gradients. Polarized optical microscopy (POM) was employed to monitor the molecular alignment, while charge carrier mobility was evaluated through organic field-effect transistor (OFET) fabrication. The platform demonstrates a straightforward approach for developing versatile organic electronic devices utilizing the responsive behavior of liquid crystal systems.