Oliogothiophenes end-capped with arylacetylenes for organic thin film transistors

Phenylethynyl, butylphenylethynyl and pentafluorophenylethynyl end-capped terthiophene oligomers (PATTP, BPATTP and FPATTP) have been synthesized and characterized. Their physical, optical and electrochemical properties varied with the end substituents were investigated. DSC results revealed that three compounds were crystalline in the film state and thermally stable by 200 °C under nitrogen atmosphere. The oligothiophenes have exhibited H-aggregation, which was verified by significant blue-shift in UV–vis absorption spectra in the films, indicating a close side-to-side molecular packing. X-ray diffraction measurement on the films has revealed molecular edge-on substrate growth orientation. Top-contact field-effect transistors were demonstrated by spin-coating or ink-jetting the solution of the oligomers. The preliminary results showed that PATTP and BPATTP can serve as p-type carriers with hole-motility as 3 × 10−4 and 1 × 10−2 cm2/(V s), respectively, while pentafluorophenylacetylene afforded FPATTP as n-type carriers with electron-motility around 10−5 cm2/(V s).