The molecular and packing structures of organic semiconductors play crucial roles in determining their charge carrier mobilities in organic field-effect transistors (OFETs). In this article, a systematic study on the functionalization of benzo[1,2-b:4,5-b′]dithiophene (BDT) with thiacycles to tune the packing, molecular orientation and semiconducting properties is reported. Among the designed BDT derivatives with six- or five-membered thiacycles containing sulphur atoms connected at the α-, β- or both α- and β-positions, the derivatives with β-sulphur atoms in the six-membered thiacycle exhibited a rubrene-like "pitched" π-stacking pattern and edge-on molecular orientation on the substrate. On the other hand, other derivatives exhibited different packing structures with a smaller intermolecular orbital overlap and end-on orientation. The thin-film OFETs based on the former molecules exhibited higher mobility than the latter, correlating the transport properties in the thin-film state with the position of the sulphur atoms and size of the thiacycles, which suggests novel molecular modification strategies in thienoacenes for the development of high performance semiconducting materials.
ASJC Scopus subject areas
- Materials Chemistry