Structural stability of naphthyl end-capped oligothiophenes in organic field-effect transistors measured by grazing-incidence X-ray diffraction in operando

Mathias Huss-Hansen, Andreas E. Lauritzen, Oier Bikondoa, Mika Torkkeli, Luciana Tavares, Matti Knaapila, Jakob Kjelstrup-Hansen

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Abstract

We report on microstructural durability of 5,5′-bis(naphth-2-yl)-2,2′-bithiophene (NaT2) in organic field-effect transistors (OFETs) in operando monitored by grazing-incidence X-ray diffraction (GIXRD). NaT2 maintains its monoclinic bulk motif in operating OFETs with a=20.31±0.06 Å, b=6.00±0.01 Å, c=8.17±0.04 Å and β=96.64±0.74°. Crystallites appear as a mosaic of single crystals reaching through the whole 50 nm thick active layer. The lattice parameters variation (<1%) falls within the statistical error of structure refinement when the OFET gate voltage is varied from 0 V to −40 V; or when the OFET is continuously cycled within this voltage interval over more than 10 h period. Within the first few cycles, both the hole mobility and threshold voltage are changing but then reach stable levels with an average mobility of (3.25±0.04)×10 −4cm 2/Vs and an average threshold voltage of −13.6±0.2 V, both varying less than 4% for the remainder of the 10 h period. This demonstrates crystalline stability of NaT2 in operating OFETs.

Original languageEnglish
JournalOrganic Electronics
Volume49
Pages (from-to)375-381
ISSN1566-1199
DOIs
Publication statusPublished - Oct 2017

Keywords

  • Grazing-incidence X-ray diffraction
  • In operando
  • Oligothiophene
  • Organic TFT

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