High-performance thin film transistors from semiconducting liquid crystalline phases by solution processes

The authors have prepared liquid crystalline (LC) semiconducting thin films with smectic phases at room temperature from 5-propyl-5(')-(4-pentylphenyl)-2,2('):5('),2(')-terthiophene (3-TTPPh-5) by spin-coating process. The films consist of large-size (approximately several tens of micrometers) LC domains with a lamellar structure. The ordering of molecular packing within the smectic layer is enhanced after annealing. The performance of thin film transistors (TFTs) based on 3-TTPPh-5 is influenced largely by silane agent modification of the dielectric. The octyltrichlorosilane (OTS) treatment enhances performance and leads to a high hole mobility of more than 4 x 10(-2) cm(2)/V s in ambient air. It is attributed to the formation of highly ordered domains with the size comparable to channel length of the TFT as well as the favorable interaction between OTS and LC molecules. (c) 2007 American Institute of Physics.