Liquid crystalline organic semiconductors for organic transistor applications

Abstract

The recent development of materials for organic field effect transistors (OFETs), including small-molecule and polymer materials, are briefly reviewed, and the problems that remain to be solved prior to practical application and use are discussed. Liquid crystalline materials are good candidates for OFETs because of their advantageous properties over soluble small-molecule materials. Liquid crystalline materials show good solution processability for the fabrication of uniform crystalline thin films using the precursor of uniform liquid crystalline thin films. In addition, liquid crystalline materials having their highly ordered liquid crystal phases show a high thermal durability despite their high solubility. The novel liquid crystalline material 2-phenyl-7-decyl[1]benzothieno[3,2-b][1]benzothiophene exhibits a highly ordered liquid crystal phase, the Smectic E (SmE) phase, which has good solution processability for uniform crystalline thin films by the precursor of uniform SmE thin films, shows high thermal durability and solubility, and can be used for transistor devices having a high mobility, over 10 cm 2 Vs -1, by thermal annealing at 120 °C for 5 min. Thus, liquid crystalline materials are good semiconductor materials for organic transistor applications instead of polymer materials.