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Benjamin Nketia-Yawson1 Yong-Young Noh1

1, Dongguk University, Seoul, SE, Korea (the Republic of)

Polymer electrolytes (e.g. ion gel) have been extensively researched for achieving high charge carrier mobility, low operation voltage and operational stability in unconventional field-effect transistors (FETs) and organic electronic devices. However, it is challenging to fabricate evaporated thin metal top gated device geometry because of the gel-like nature. Ion diffusion into the semiconducting film also interferes fundamental charge transport during operation. Here we develop a new high-capacitance polymeric solid-state ionic gate dielectrics prepared by a controlled blend consisting of the high-k and low-k polymers (e.g. P(VDF-TrFE), P(VDF-HFP), PMMA etc.) and the ion gel based on poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP) with 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [EMIM][TFSI] ionic liquid. Our engineered solid polymer electrolytes show huge capacitance values > 4 μF/cm2, which allows high drive current at low driving voltages and also allow the direct deposition of a conductive top-gate electrode by any methods such as thermal evaporation and printing. Vacuum-metalized top gate FETs with the solid-state ionic dielectrics showed excellent carrier mobilities in a range of 3-20 cm2V-1s-1 for an ample set of common p-type conjugated polymers, and 2-10 cm2V-1s-1 for Indium gallium zinc oxide (IGZO) FET devices operating at ≤ 2 V. We also observed ambipolar charge transport in n-type conjugated polymers with electron mobility in the order of 10-2~10-3cm2V-1s-1 and a remarkable hole mobility of 0.14±0.02 cm2V-1s-1 in naphthalene diimide (NDI)-based conjugated polymer owing to the large hole accumulation compared to ~0.03cm2V-1s-1 using neat PMMA gate dielectric. These remarkable FET performances review the dependency on the ionic content, semiconductor, device dimensions, top metal gate electrode, and bulk polymer dielectric among others. Our solid-state ionic gate dielectrics allow us to achieve high charge-carrier mobility at low driving voltages and demonstrate a good candidate for realizing low-power, flexible and wearable electronics.

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