Dibenzo[b,d]thiophene based oligomers with carbon–carbon unsaturated bonds for high performance field-effect transistors

Dibenzo[b,d]thiophene (DBT) based oligomers with carbon–carbon double and triple bonds were synthesized. Their thermal stability and energy levels were studied by thermal analyses, UV–vis absorption spectra and electrochemistry. Single crystals of 3,7-bis(phenylethynyl)dibenzo[b,d]thiophene (BEDBT) revealed the introduction of unsaturated bonds eliminated the steric repulsion between adjacent aromatic rings and BEDBT displayed planar structure in crystals. Thin film transistors of these compounds displayed typical p-type behaviour. The best performance was obtained from 3,7-distyryldibenzo[b,d]thiophene (DSDBT) on OTS modified substrates with mobility as high as 0.15 cm2/Vs and on/off current ratio up to 108, one of the highest performance for DBT based oligomers.