Pentafluorophenyl end-capped bithiophene imide (BTI) based n-type semiconductors for organic thin-film transistors

Abstract

Two novel small molecular organic semiconductors, DFP-BTI-b8 (1) and DFP-BTI-b16 (2), composed of bithiophene imide (BTI) end-capped with pentafluorophenyl (FP) bearing solubilizing alkyl side chains, were successfully synthesized, and their structural, optical, and electrical properties were characterized to evaluate their potential for organic thin-film transistor applications. The single crystal structures of compounds 1 and 2 were obtained and revealed the well-organized packing with strong π–π interactions. Both DFP-BTIs exhibit outstanding n-type OTFT performance with mobilities of up to 0.10 cm² V⁻¹ s⁻¹ and current on/off ratios over 10⁶, placing them among the high-performance BTI-based small molecular organic semiconductors reported to date. This efficient charge transport demonstrates that the molecular design effectively balances solubility and crystallinity. Atomic force microscopy (AFM) and X-ray diffraction (XRD) demonstrated that the planar nature of DFP-BTIs, driven by strong H⋯F interactions, promotes highly ordered polycrystalline thin-films, contributing to such excellent field-effect properties. Overall, these results demonstrate that fluorinated BTI-based materials are promising n-type semiconductors for stable and solution-processable OTFT devices.