title: Freezing-in orientational disorder induces crossover from thermally-activated to temperature-independent transport in organic semiconductors.
abstract: The crystalline structure of organic materials dictates their physical properties, but while significant research effort is geared towards understanding structure-property relationships in such materials, the details remain unclear. Many organic crystals exhibit transitions in their electrical properties as a function of temperature. One example is the 1:1 charge-transfer complex trans--stilbene-2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane. Here we show that the mobility and resistivity of this material undergo a transition from being thermally activated at temperatures above 235 K to being temperature independent at low temperatures. On the basis of our experimental and theoretical results, we attribute this behaviour to the presence of a glass-like transition and the accompanied freezing-in of orientational disorder of the stilbene molecule.
authors.affiliation: Department of Physics, Wake Forest University, Winston-Salem, North Carolina 27109, USA.
authors.forename: K P
authors.initials: KP
authors.lastname: Goetz
authors.affiliation: School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
authors.forename: A
authors.initials: A
authors.lastname: Fonari
authors.affiliation: Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA.
authors.forename: D
authors.initials: D
authors.lastname: Vermeulen
authors.affiliation: School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore.
authors.forename: P
authors.initials: P
authors.lastname: Hu
authors.affiliation: School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore.
authors.forename: H
authors.initials: H
authors.lastname: Jiang
authors.affiliation: Department of Physics, Wake Forest University, Winston-Salem, North Carolina 27109, USA.
authors.forename: P J
authors.initials: PJ
authors.lastname: Diemer
authors.affiliation: Department of Physics, Wake Forest University, Winston-Salem, North Carolina 27109, USA.
authors.forename: J W
authors.initials: JW
authors.lastname: Ward
authors.affiliation: Department of Physics, Wake Forest University, Winston-Salem, North Carolina 27109, USA.
authors.forename: M E
authors.initials: ME
authors.lastname: Payne
authors.affiliation: Department of Chemistry, Wake Forest University, Winston-Salem, North Carolina 27109, USA.
authors.forename: C S
authors.initials: CS
authors.lastname: Day
authors.affiliation: School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore.
authors.forename: C
authors.initials: C
authors.lastname: Kloc
authors.affiliation: School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
authors.forename: V
authors.initials: V
authors.lastname: Coropceanu
authors.affiliation: Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA.
authors.forename: L E
authors.initials: LE
authors.lastname: McNeil
authors.affiliation: Department of Physics, Wake Forest University, Winston-Salem, North Carolina 27109, USA.
authors.forename: O D
authors.initials: OD
authors.lastname: Jurchescu