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

• DOI: 10.1016/j.orgel.2017.07.012
• Publication Date: 2017-07-08T20:48:33Z
• Authors: Mathias K. Huss-H...; Andreas E. Lauritzen; Oier Bikondoa; Mika Torkkeli; Luciana Tavares; Matti Knaapila; Jakob Kjelstrup-H...
• Keywords: Organic TFT; Grazing-incidence X-ray diffraction; TK; 02 engineering and technology; In operando; 0210 nano-technology; Oligothiophene

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 View the MathML source 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.\ud \ud