Vinylene spacer effects of benzothiadiazole–quarterthiophene based conjugated polymers on transistor mobilities

Abstract

In this work we aim to investigate the relationships among the ratios of vinyl linker, crystallinity and charge carrier mobility in a series of benzothiadiazole–quarterthiophene based conjugated polymers. Four polymers, PB4TV0, PB4TV1, PB4TV2 and PB4TV3, containing 0 to 3 vinyl linkers in the repeating unit were synthesized, and their corresponding bottom gate/bottom contact organic field effect transistors were fabricated and examined. The results manifest escalating hole mobilities along the increasing ratio of vinyl linker, with PB4TV3 reaching a high hole mobility up to 0.36 cm² V⁻¹ s⁻¹. On the other hand, further investigations have revealed a gradual reduction in the crystallinity with rising vinyl ratio after a slight enhancement at first. The difference between the mobility and crystallinity variation tendency is caused by the combined influences of intra-chain charge transport enhancement and the conformational isomerization nature of the vinyl linker, which could provide new thoughts in designing high performance conjugated polymers for OFETs in future.