Directional Carrier Polarity Tunability in Ambipolar Organic Transistors Based on Diketopyrrolopyrrole and Bithiophene Imide Dual-Acceptor Semiconducting Polymers

An organic ambipolar transistor allows the integration of p-type and n-type charge carrier transport in a single device. However, the tunability of carrier polarity to meet specific requirements for practical applications is challenging and thus rarely studied. In this work, two dual-acceptor-type polymers (FuI and SeI) based on diketopyrrolopyrrole (DPP) and bithiophene imide (BTI) are reported. By varying the flanking groups of DPP (furan for FuI and selenophene for SeI) and through an ionic additive strategy, the charge carrier polarity of both polymers in organic field-effect transistors (OFETs) can be directionally tuned. Specifically, pristine polymers exhibited an ambipolar property with the μ_e/μ_h values of 2.79 for FuI and 4.9 for SeI. Notably, the average electron mobility of SeI reaches as high as 0.122 cm² V^–1 s^–1. More encouragingly, with 11.76% tetrabutylammonium iodide (TBAI, mole percentage) as an additive to the FuI polymer, the μ_e/μ_h of resultant OFETs varied from 2.79 to 0.71, showing the conversion from n-type dominant to p-type dominant transport. With the same mole percentage of the TBAI to SeI polymer, a dramatic increment of μ_e/μ_h from 4.9 to 264 was observed, demonstrating the significant conversion from n-type dominant ambipolar to unipolar n-type transport. Overall, this study demonstrates the possibility of directional tunability of carrier polarity in organic ambipolar transistors with DPP- and BTI-based dual-acceptor polymers through molecular modification and the ionic additive strategy, being significantly beneficial for complementary circuits.