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

Abstract

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.