Thin film transistors (TFTs) with ionic liquid gate dielectrics, [1-ethyl-3-methylimidazolium][bis(trifluoromethanesulfonyl)imide] (emim[TFSI]) and [1-butyl-3-methylimidazolium][hexafluorophosphate] (bmim[PF6]), are fabricated with thin films of one dimensional (1D) hydrocarbon, [7]phenacene. P-channel characteristics are observed for [7]phenacene TFTs with both ionic liquids by use of platinum electrode. The field-effect mobility μ for [7]phenacene TFT with bmim[PF6] was recorded to be 0.28 cm2 V−1 s−1. The value of absolute threshold voltage, |VTH|, was less than 2.5 V, showing low-voltage operation. The accumulation of hole in the [7]phenacene TFTs with ionic liquids was confirmed from the voltage or time dependence of capacitance in metal–insulator-semiconductor structure, which shows that these TFTs operate electrochemically and the carriers are accumulated in the whole of [7]phenacene thin films.Graphical abstractHighlights► We made aromatic hydrocarbon ([7]phenacene) electrochemical transistor with ionic liquids. ► Low voltage operation and high field-effect mobility was realized in [7]phenacene electrochemical transistor. ► Availability of bmim[PF6] gel for electrochemical transitor was shown. ► Future prospective is shown for application of aromatic hydrocarbon electrochemical transistor.

•Fabrication of field-effect transistors with single crystals of new phenacene molecules.•Achievement of high field-effect mobility and low voltage operation in single crystal field-effect transistors.•Interface modification with electron-acceptor molecules to improve the transistor performance.Single crystal field-effect transistors (FETs) using [6]phenacene and [7]phenacene show p-channel FET characteristics. Field-effect mobilities, μs, as high as 5.6 × 10−1 cm2 V−1 s−1 in a [6]phenacene single crystal FET with an SiO2 gate dielectric and 2.3 cm2 V−1 s−1 in a [7]phenacene single crystal FET were recorded. In these FETs, 7,7,8,8-tetracyanoquinodimethane (TCNQ) was inserted between the Au source/drain electrodes and the single crystal to reduce hole-injection barrier heights. The μ reached 3.2 cm2 V−1 s−1 in the [7]phenacene single crystal FET with a Ta2O5 gate dielectric, and a low absolute threshold voltage |VTH| (6.3 V) was observed. Insertion of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) in the interface produced very a high μ value (4.7–6.7 cm2 V−1 s−1) in the [7]phenacene single crystal FET, indicating that F4TCNQ was better for interface modification than TCNQ. A single crystal electric double-layer FET provided μ as high as 3.8 × 10−1 cm2 V−1 s−1 and |VTH| as low as 2.3 V. These results indicate that [6]phenacene and [7]phenacene are promising materials for future practical FET devices, and in addition we suggest that such devices might also provide a research tool to investigate a material’s potential as a superconductor and a possible new way to produce the superconducting state.Graphical abstract