title: Tristable electrical conductivity switching in a polyfluorene-diphenylpyridine copolymer with pendant carbazole groups.
abstract: Tristable electrical conductivity switching and non-volatile memory effects are demonstrated in a conjugated copolymer of poly(2,6-diphenyl-4-((9-ethyl)-9H-carbazole)-pyridinyl-alt-2,7-(9,9-didodecyl)-9H-fluorenyl) (PPCzPF). The indium-tin oxide (ITO)/PPCzPF/Al device can be switched from the low-conductivity (off) state to the first high-conductivity (on-1) state at 1.8 V, with an on/off current ratio of approximately 100. The device can be further switched from the on-1 state to the next higher conductivity (on-2) state at 2.4 V, with an on-2/on-1 current ratio of approximately 20. All the three conductivity states are accessible, stable and non-erasable. The tri-level conductance switching can be explained in terms of field-induced conformational ordering of the polymer chains and enhanced charge-transfer interaction at the PPCzPF/ITO interface.
authors.affiliation: Department of Chemical and Biomolecular Engineering, National University of Singapore, Kent Ridge, Singapore 119260, Republic of Singapore.
authors.forename: Gang
authors.initials: G
authors.lastname: Liu
authors.forename: Der-Jang
authors.initials: DJ
authors.lastname: Liaw
authors.forename: Wei-Yi
authors.initials: WY
authors.lastname: Lee
authors.forename: Qi-Dan
authors.initials: QD
authors.lastname: Ling
authors.forename: Chun-Xiang
authors.initials: CX
authors.lastname: Zhu
authors.forename: D Siu-Hung
authors.initials: DS
authors.lastname: Chan
authors.forename: En-Tang
authors.initials: ET
authors.lastname: Kang
authors.forename: Koon-Gee
authors.initials: KG
authors.lastname: Neoh