3B12 Polycrystalline thin film transistors of mono alkylated liquid crystalline Ph-BTBT derivatives : dependence of alkyl chain length on processability and characteristics

Abstract

We have investigated processability of mono-alkylated Phenyl-benzothienobenzothiophene (Ph-BTBT) derivatives having various alkyl chain lengths from C₆ to C₁₄ in fabrication of polycrystalline thin films by solution process and their characteristics of field effect transistor (FET). All Ph-BTBT derivatives show smectic E (SmE) phase and give uniform polycrystalline thin film easily when the SmE films are used as a precursor. The Ph-BTBT derivatives having short alkyl chain lengths show high solubility and good solution processability because they exhibit SmE phase at low temperatures, while Ph-BTBT having long alkyl chain length show relatively low solubility, but give high FET mobility over 15 cm²/Vs after thermal annealing.