THIN-FILM TRANSISTORS BASED ON ALPHA-CONJUGATED OLIGOMERS

Thin-film transistors (TFTs) were fabricated with various conjugated organic oligomers. The devices operate in the enrichment mode, where an accumulation layer forms at the insulator-semiconductor interface under the effect of the gate voltage. The field-effect mobility is very sensitive to the nature and chain length of the oligomers. No field-enhanced current is observed on short chains. The field-effect starts with five rings on polyacenes and oligothienylenes, whereas no field-effect is obtained with the para-oligophenylenes up to sexiphenyl. This shows that the electrical properties of the oligomers are clearly related to their degree of conjugation.