Authors Karpov, Y. ; Zhao, W. ; Raguzin, I. ; Beryozkina, T. ; Bakulev, V. ; Al-Hussein, M. ; Häußler, L. ; Stamm, M. ; Voit, B. ; Facchetti, A. ; Tkachov, R. ; Kiriy, A.
Title Influence of semiconductor thickness and molecular weight on the charge transport of a naphthalenediimide-based copolymer in thin-film transistors
Date 03.07.2015
Number 46782
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.
Publisher ACS Applied Materials & Interfaces
Identifier 17
Citation ACS Applied Materials & Interfaces 7 (2015) 12478-12487
Tags semiconducting polymer thin-film transistor electron mobility morphology crystallinity field-effect transistors chain-growth polymerization heterojunction solar-cells one-pot synthesis high-mobility conjugated polymer organic transistors printed transisto

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