Liquid crystallinity of Ph-BTBT derivatives having improved solubility and their transistor characteristics

Abstract

We have investigated the liquid crystallinity, thin film fabrication, and FET characteristics of mono alkyl phenylbenzothienobenzothiophene (Ph-BTBT) derivatives having an oxygen atom in side chain in order to improve the solubility. Synthesized Ph-BTBT derivatives show highly ordered liquid crystal (SmE) phase and increase of solubility. It is found that polycrystalline thin film with uniformity and flat-surface morphology was easily formed using liquid crystalline films as a precursor by solution process. The FET mobility was evaluated from transfer characteristics of the FETs. Ph-BTBT derivatives having longer side chain, Ph-BTBT-12O-1, showed high FET mobility of 13 cm2/Vs. We conclude that the idea using alkoxy-substituted side chain can improve the solubility effectively, while keeping high FET mobility of over 10cm2/Vs.