High-mobility organic thin-film transistors based on α,α′-didecyloligothiophenes

We have fabricated organic thin-film transistors and integrated circuits baked on the small-molecule organic semiconductors alpha,alpha'-didecylquaterthiophene, alpha,alpha'-didecylquinquethiophene, and alpha,alpha'-didecylsexithiophene. The organic semiconductors were deposited by thermal evaporation, with solution-processed and cross linked poly-4-vinylphenol serving as the gate dielectric layer. We have found that bottom-contact devices based on these materials have better electrical performance than top-contact devices, presumably due to more efficient carrier injection from bottom contacts due to the presence of the relatively long alkyl chains substituted at the alpha- and omega-positions of the oligothiophene molecules. Bottom-contact transistors have carrier mobility as large as 0.5 cm(2)/V s and on/off current ratio as large as 10(5), and ring oscillators fabricated using bottom-contact transistors and alpha,alpha'didecylsexithiophene as the organic active layer have signal propagation delay as low as 30 mus per stage. (C) 2003 American Institute of Physics.