title: High capacitance, photo-patternable ion gel gate insulators compatible with vapor deposition of metal gate electrodes.
abstract: A facile fabrication route to pattern high-capacitance electrolyte thin films in electrolyte-gated transistors (EGTs) was demonstrated using a photoinitiated cross-linkable ABA-triblock copolymer ion gel. The azide groups of poly(styrene-r-vinylbenzylazide) (PS-N3) end-blocks can be chemically cross-linked via UV irradiation (λ = 254 nm) in the self-assembly of poly[(styrene-r-vinylbenzylazide)-b-ethylene oxide-b-(styrene-r-vinylbenzylazide)] (SOS-N3) triblock copolymer in the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMI][TFSI]). Impedance spectroscopy and small-angle X-ray scattering revealed that ion transport and microstructure of the ion gel are not affected by UV cross-linking. Using a photoinduced cross-linking strategy, photopatterning of ion gels through a patterned mask was achieved. Employing a photopatterned ion gel as the high-capacitance gate insulator in thin film transistors (TFTs), arrays of TFTs exhibited uniform and high device performance. Specifically, both p-type (poly(3-hexylthiophene)) (P3HT) and n-type (ZnO) transistors displayed high carrier mobility (hole mobility of ∼ 1.4 cm(2)/ (V s) and electron mobility of ∼ 0.7 cm(2)/ (V s) and ON/OFF current ratio (∼ 10(5)) at supply voltages below 2 V. This study suggests that photopatterning is a promising candidate to conveniently incorporate high-capacitance ion gels into TFTs in the fabrication of printed electronics.
authors.affiliation: Department of Chemistry, University of Minnesota , 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States.
authors.forename: Jae-Hong
authors.initials: JH
authors.lastname: Choi
authors.forename: Yuanyan
authors.initials: Y
authors.lastname: Gu
authors.forename: Kihyon
authors.initials: K
authors.lastname: Hong
authors.forename: Wei
authors.initials: W
authors.lastname: Xie
authors.forename: C Daniel
authors.initials: CD
authors.lastname: Frisbie
authors.forename: Timothy P
authors.initials: TP
authors.lastname: Lodge
keywords: chemical cross-linking; ion gel; metal gate electrode; photopatterning; thin-film transistor