title: Oriented Liquid Crystalline Polymer Semiconductor Films with Large Ordered Domains.
abstract: Large strains are applied to liquid crystalline poly(2,5-bis(3-tetradecylthiophen-2yl)thieno(3,2-b)thiophene) (pBTTT) films when held at elevated temperatures resulting in in-plane polymer alignment. We find that the polymer backbone aligns significantly in the direction of strain, and that the films maintain large quasi-domains similar to that found in spun-cast films on hydrophobic surfaces, highlighted by dark-field transmission electron microscopy imaging. The highly strained films also have nanoscale holes consistent with dewetting. Charge transport in the films is then characterized in a transistor configuration, where the field effect mobility is shown to increase in the direction of polymer backbone alignment, and decrease in the transverse direction. The highest saturated field-effect mobility was found to be 1.67 cm(2) V(-1) s(-1), representing one of the highest reported mobilities for this material system. The morphology of the oriented films demonstrated here contrast significantly with previous demonstrations of oriented pBTTT films that form a ribbon-like morphology, opening up opportunities to explore how differences in molecular packing features of oriented films impact charge transport. Results highlight the role of grain boundaries, differences in charge transport along the polymer backbone and π-stacking direction, and structural features that impact the field dependence of charge transport.
authors.affiliation: Department of Mechanical and Aerospace Engineering, North Carolina State University , Raleigh, North Carolina 27695, United States.
authors.forename: Xiao
authors.initials: X
authors.lastname: Xue
authors.affiliation: Department of Mechanical and Aerospace Engineering, North Carolina State University , Raleigh, North Carolina 27695, United States.
authors.forename: George
authors.initials: G
authors.lastname: Chandler
authors.affiliation: Institute for Soft Matter Synthesis & Metrology, Department of Physics, Georgetown University , Washington, DC 20057, United States.
authors.forename: Xinran
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Material Measurement Laboratory, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States.
authors.forename: R Joseph
authors.initials: RJ
authors.lastname: Kline
authors.affiliation: Department of Chemistry and Centre for Plastic Electronics, Imperial College London , London Sw7 2AZ, United Kingdom.
authors.forename: Zhuping
authors.initials: Z
authors.lastname: Fei
authors.affiliation: Department of Chemistry and Centre for Plastic Electronics, Imperial College London , London Sw7 2AZ, United Kingdom.
authors.forename: Martin
authors.initials: M
authors.lastname: Heeney
authors.affiliation: Department of Physics, Wake Forest University , Salem, North Carolina 27109, United States.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Diemer
authors.affiliation: Department of Physics, Wake Forest University , Salem, North Carolina 27109, United States.
authors.forename: Oana D
authors.initials: OD
authors.lastname: Jurchescu
authors.affiliation: Department of Mechanical and Aerospace Engineering, North Carolina State University , Raleigh, North Carolina 27695, United States.
authors.forename: Brendan T
authors.initials: BT
authors.lastname: O'Connor
keywords: charge transport; oriented film; pBTTT; polymer semiconductors