Organic field-effect transistors based on two phenylene–thiophene oligomer derivatives with a biphenyl or fluorene core

► Two phenylene–thiophene oligomer derivatives were synthesized. ► New oligomers have large band gaps, low HOMO levels, and high stabilities. ► Two oligomers were investigated for OFET devices. ► A mobility of 0.2cm2/Vs was achieved for the oligomer with a biphenyl core. The synthesis and full characterization are described of two phenylene–thiophene oligomer derivatives, 2,7-bis[5-(4-n-hexylphenyl)-2-thienyl]fluorene (HPTFTPH) and 4,4′-bis[5-(4-n-hexylphenyl)-2-thienyl]biphenyl (HPTPPTPH), which are based on a structural combination of a fluorene or biphenyl core, thienyl units, and end-cap hexylphenyl groups. Remarkable shifts in the UV–vis and photoluminescence spectra of thin films relative to their solutions indicate the existence of strong intermolecular π–π interactions in the solid state of the two oligomers. In addition, relatively large energy gaps and low highest occupied molecular orbital energy levels imply that the two oligomers are promising and durable semiconducting materials. Thin-film organic field-effect transistor devices based on the two oligomers show good p-type performances with high hole mobilities. The highest mobility (0.20cm2/Vs) was obtained for the HPTPPTPH oligomer with biphenyl core.