title: Solution-processed barium salts as charge injection layers for high performance N-channel organic field-effect transistors.
abstract: N-channel organic field-effect transistors (OFETs) have generally shown lower field-effect mobilities (μFET) than their p-type counterparts. One of the reasons is the energetic misalignment between the work function (WF) of commonly used charge injection electrode, i.e. gold (Au), and the lowest unoccupied molecular orbital (LUMO) of n-channel electron-transporting organic semiconductors. Here, we report barium salts as solution-processed interlayers, to improve the electron-injection and/or hole-blocking in top-gate/bottom-contact n-channel OFETs, based on poly{[N,N'-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-dithiophene)} (P(NDI2OD-T2)) and phenyl-C61-butyric acid methyl ester (PC61BM). Two different barium salts, barium hydroxide (Ba(OH)2) and barium chloride (Ba(Cl)2), are employed as the ultrathin interlayer (∼2 nm); and they effectively tune the WF of Au from 4.9 eV, to as low as 3.5 eV. The resulting n-channel OFETs exhibit significantly improved μFET, approaching 2.6 cm(2)/(V s) and 0.1 cm(2)/(V s) for the best P(NDI2OD-T2) and PC61BM devices, respectively, with Ba(OH)2 as interlayer.
authors.affiliation: Department of Nanobio Materials and Electronics, School of Material Science and Engineering, Heeger Center for Advanced Materials, Gwangju Institute of Science and Technology (GIST) , 261 Cheomdan-gwagiro (Oryong-dong), Buk-gu, Gwangju 500-712, Republic of Korea.
authors.forename: Nam-Koo
authors.initials: NK
authors.lastname: Kim
authors.forename: Dongyoon
authors.initials: D
authors.lastname: Khim
authors.forename: Yong
authors.initials: Y
authors.lastname: Xu
authors.forename: Seung-Hoon
authors.initials: SH
authors.lastname: Lee
authors.forename: Minji
authors.initials: M
authors.lastname: Kang
authors.forename: Jihong
authors.initials: J
authors.lastname: Kim
authors.forename: Antonio
authors.initials: A
authors.lastname: Facchetti
authors.forename: Yong-Young
authors.initials: YY
authors.lastname: Noh
authors.forename: Dong-Yu
authors.initials: DY
authors.lastname: Kim