Liquid crystalline thin films as a precursor for polycrystalline thin films aimed at field effect transistors

Abstract

We have investigated the availability of liquid crystalline thin films as a precursor of quality polycrystalline thin films for organic field effect transistors (OFETs) by solution process. The experiments of spin-coating at various temperatures proved that the morphology of resulting polycrystalline thin films at room temperature strongly depend on what the films immediately after spin-coating and solvent evaporation at those temperatures were, i.e., crystal, liquid crystal, or isotropic liquid. The polycrystalline films spin-coated at the temperatures for crystal and isotropic liquid phases were much roughened owing to many small crystal flakes and droplets. On the other hand, the thin films spin-coated at liquid crystal temperatures were very uniform in a whole area and showed high FET mobility having a small variation from device to device.