High-mobility amorphous PTB7 organic transistors enabled by high-capacitance electrolyte dielectric

Applied Physics Letters, Volume 119, Issue 4, July 2021. Molecular engineering of organic semiconductors through different synthetic routes has remarkably improved the understanding of the structure–property relationship and charge transport physics, particularly in organic field-effect transistors (OFETs). Emerging OFETs with reliable charge-carrier mobilities exceeding >1 cm2 V−1 s−1 have been demonstrated. However, the field-effect mobilities of amorphous conjugated polymer semiconductors have still showed the values below 10−2 cm2 V−1 s−1 over the past two decades. Here, we report on highly reproducible amorphous organic PTB7 transistors with an exceptional mobility of 0.80 cm2 V−1 s−1 (μavg ≈ 0.51 ± 0.16 cm2 V−1 s−1) operating at 2 V comparable to that of inorganic amorphous silicon semiconductor devices (0.5–1 cm2 V−1 s−1). This remarkable performance is enabled by the use of high-capacitance electrolyte dielectric (Ci = 48.42 μF cm−2), allowing easily attainable lower contact resistance of < 400 Ω cm and improved charge carrier density in the transistor channel, compared to those fabricated using low-k poly(methyl methacrylate) (Ci = 6.2 nF cm−2) and high-k poly(vinylidene fluoride-co-hexafluoropropylene) (Ci = 49.8 nF cm−2) gate dielectrics. This work contributes an opportunity for understanding and improving device performances of amorphous conjugated polymer semiconductors.