title: Influence of Semiconductor Thickness and Molecular Weight on the Charge Transport of a Naphthalenediimide-Based Copolymer in Thin-Film Transistors.
abstract: The N-type semiconducting polymer, P(NDI2OD-T2), with different molecular weights (MW=23, 72, and 250 kg/mol) was used for the fabrication of field-effect transistors (FETs) with different semiconductor layer thicknesses. FETs with semiconductor layer thicknesses from ∼15 to 50 nm exhibit similar electron mobilities (μ's) of 0.2-0.45 cm2 V(-1) s(-1). Reduction of the active film thickness led to decreased μ values; however, FETs with ∼2 and ∼5 nm thick P(NDI2OD-T2) films still exhibit substantial μ's of 0.01-0.02 and ∼10(-4) cm2 V(-1) s(-1), respectively. Interestingly, the lowest molecular weight sample (P-23, MW≈23 kg/mol, polydispersity index (PDI)=1.9) exhibited higher μ than the highest molecular weight sample (P-250, MW≈250 kg/mol, PDI=2.3) measured for thicker devices (15-50 nm). This is rather unusual behavior because typically charge carrier mobility increases with MW where improved grain-to-grain connectivity usually enhances transport events. We attribute this result to the high crystallinity of the lowest MW sample, as confirmed by differential scanning calorimetry and X-ray diffraction studies, which may (over)compensate for other effects.
authors.affiliation: †Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, 01069 Dresden, Germany.
authors.forename: Yevhen
authors.initials: Y
authors.lastname: Karpov
authors.affiliation: ‡Polyera Corporation, Skokie, Illinois 60077, United States.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhao
authors.affiliation: †Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, 01069 Dresden, Germany.
authors.forename: Ivan
authors.initials: I
authors.lastname: Raguzin
authors.affiliation: §Ural Federal University, Mira Street 28, 620002, Yekaterinburg, Russia.
authors.forename: Tetyana
authors.initials: T
authors.lastname: Beryozkina
authors.affiliation: §Ural Federal University, Mira Street 28, 620002, Yekaterinburg, Russia.
authors.forename: Vasiliy
authors.initials: V
authors.lastname: Bakulev
authors.affiliation: ⊥Physics Department, The University of Jordan, Amman 11942, Jordan.
authors.forename: Mahmoud
authors.initials: M
authors.lastname: Al-Hussein
authors.affiliation: †Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, 01069 Dresden, Germany.
authors.forename: Liane
authors.initials: L
authors.lastname: Häußler
authors.affiliation: †Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, 01069 Dresden, Germany.|∥Center for Advancing Electronics Dresden (CFAED), Technische Universität Dresden, 01062 Dresden, Germany.
authors.forename: Manfred
authors.initials: M
authors.lastname: Stamm
authors.affiliation: †Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, 01069 Dresden, Germany.|∥Center for Advancing Electronics Dresden (CFAED), Technische Universität Dresden, 01062 Dresden, Germany.
authors.forename: Brigitte
authors.initials: B
authors.lastname: Voit
authors.affiliation: ‡Polyera Corporation, Skokie, Illinois 60077, United States.|#Center of Excellence for Advanced Materials Research (CEAMR), King Abdulaziz University, P.O. Box 80203, Jeddah, Saudi Arabia 21589.
authors.forename: Antonio
authors.initials: A
authors.lastname: Facchetti
authors.affiliation: †Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, 01069 Dresden, Germany.
authors.forename: Roman
authors.initials: R
authors.lastname: Tkachov
authors.affiliation: †Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, 01069 Dresden, Germany.
authors.forename: Anton
authors.initials: A
authors.lastname: Kiriy
keywords: crystallinity; electron mobility; morphology; semiconducting polymer; thin-film transistor