Dibenzothienobisbenzothiophene-a novel fused-ring oligomer with high field-effect mobility

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Abstract
Conjugated oligomers with rigid, fused-ring structure are of interest for organic field-effect transistors where strong π-π interaction between adjacent molecules is required to obtain high charge carrier mobilities. Dibenzo[b,b′]thieno[2,3-f:5,4-f′]bis[1]benzothiophene (DBTBT) has been synthesized by a novel route, the key step of which is the acid-induced intramolecular cyclization reaction of aromatic methyl sulfoxides. Field-effect transistors (FETs) with thin, polycrystalline DBTBT films deposited by vacuum sublimation exhibit high field-effect mobilities of 0.15 cm 2 (Vs) –1 and ON-OFF current ratios >10 6 . The coupling reaction is not regioselective and different regioisomers have been identified. Degraded FET performance is observed when the sublimed films contain a mixture of different isomers.