Cyclopentadithiophene-benzothiadiazole oligomers: Synthesis via direct arylation, X-ray crystallography, optical properties, solution casted field-effect transistor and photovoltaic characteristics

► Conjugated oligomers are synthesised via direct arylation and Suzuki coupling. ► Molecular structure of the oligomer is investigated by X-ray single crystallography. ► Bulk-hetero junction OPV devices of the oligomer blended with PCBM are fabricated. ► The oligomer is used as a sensitiser in a blend with P3HT-PCBM or PCPDTBT-PCBM. ► The power conversion efficiency can be improved in the presence of the oligomer.