The nature of the interface between the gate dielectric and organic semiconductor material in organic thin-film transistors has a significant impact on the resulting device characteristics, and therefore careful design and engineering is required to optimize device performance. In this study, we demonstrate organic modifiers based on space-filling paraffinic tripodal triptycenes, which form a self-assembled, completely oriented 2D (hexagonal triptycene array) + 1D (layer stacking) structure on polymers. When a thin layer of the species is deposited onto the gate dielectric material, it acts as a universal surface energy modifier, yielding surface energies of 22.2 mJ/m2 regardless of the gate dielectric species. Consequently, the thin layer triptycene film was also applied to the gate dielectric layers of low-operating voltage OTFTs with a DNTT channel layer, and to integrated circuits constructed from these devices. Device characteristics were enhanced by the triptycene layer, while modification was not found to change the operating voltage of either the OTFTs or the circuits: the organic CMOS ring oscillator circuits operated at low voltages of just 0.8 V, and exhibited single-stage signal delay values of 9 μs at 10 V. To our knowledge, this is the lowest delay value among low-voltage, organic CMOS ring oscillators based on devices using polymer gate dielectrics.
This work was supported by the Someya Bio-Harmonized ERATO grant.
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