Changes of the Molecular Structure in Organic Thin Film Transistors during Operation

Liscio, Fabiola; Ferlauto, Laura; Matta, Micaela; Pfattner, Raphael; Murgia, Mauro; Rovira, Concepció; Mas‐Torrent, Marta; Zerbetto, Francesco; Milita, Silvia; Biscarini, Fabio

doi:10.1021/acs.jpcc.5b03901

Cited by 11 publications

(18 citation statements)

References 45 publications

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“…The flexible alkyl chains of DP2TN seem to lower the degree of order in plane and this is manifested in the GIXRD data by verti-cal streaks (Bragg rods) characteristic for a liquid crystalline like order. The Bragg rods are also observed in pentacene films [13]. Similar streaks are not observed for NaT2 but the peaks are equally resolved for all three directions.…”

Section: Resultssupporting

confidence: 68%

“…Our objectives are to study Na2T in the OFET environment; demonstrate the versatility of GIXRD when probing OFETs in operando; and seek for electric field induced effects like those reported by Liscio et al [13]. We find NaT2 forming a mosaic of essentially monoclinic single crystals through the whole active layer.…”

Section: Introductionmentioning

confidence: 66%

“…The location of the traps has for example been suggested to be at grain boundaries of the organic layer [8,9] or at the dielectric/semiconductor interface [10], and it has been determined that water plays a role [11,12], even though the bias-stress also occurs under vacuum conditions. Recently Liscio and co-workers [13] employed grazing-incidence X-ray diffraction (GIXRD) to study pentacene OFETs in operando, and proposed that an applied electric field could reorient a fraction of the pentacene molecules located at or near grain boundaries leading to energy lowering and the formation of a shallow trap for charge carriers that would influence bias-stress stability.…”

Section: Introductionmentioning

confidence: 99%

“…This structure is further modified by an additional molecular layer between electrodes and thiophene layer [19] or altered by external parameters such as externally induced uniaxial strain [20]. The structure of various oligothiophenes in OFETs has been resolved ex situ even in the monolayer level [16] but the effect of electric field in running OFETs, corresponding those observed for pentance [13], are not well reported.…”

Section: Introductionmentioning

confidence: 99%

“…However, apart from the GIXRD studies of Liscio and co-workers [13] the GIXRD literature of OFETs in operando is less comprehensive.…”

Section: Introductionmentioning

confidence: 99%

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

Huss-Hansen

Lauritzen

Bikondoa

et al. 2017

Organic Electronics

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. (2017) Structural stability of naphthyl end-capped oligothiophenes in organic field-effect transistors measured by grazingincidence X-ray diffraction in operando. Organic Electronics. Permanent WRAP URL:http://wrap.warwick.ac.uk/89989 Copyright and reuse:The Warwick Research Archive Portal (WRAP) makes this work by researchers of the University of Warwick available open access under the following conditions. Copyright © and all moral rights to the version of the paper presented here belong to the individual author(s) and/or other copyright owners. To the extent reasonable and practicable the material made available in WRAP has been checked for eligibility before being made available.Copies of full items can be used for personal research or study, educational, or not-for-profit purposes without prior permission or charge. Provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. A note on versions:The version presented here may differ from the published version or, version of record, if you wish to cite this item you are advised to consult the publisher's version. Please see the 'permanent WRAP URL' above for details on accessing the published version and note that access may require a subscription. AbstractWe 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 ± 0.06Å, b = 6.00 ± 0.01Å, c = 8.17 ± 0.04Å 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 −4 cm 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.

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Section: Resultssupporting

confidence: 68%

Section: Introductionmentioning

confidence: 66%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…However, apart from the GIXRD studies of Liscio and co-workers [13] the GIXRD literature of OFETs in operando is less comprehensive.…”

Section: Introductionmentioning

confidence: 99%

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

Huss-Hansen

Lauritzen

Bikondoa

et al. 2017

Organic Electronics

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Substrate‐Induced and Thin‐Film Phases: Polymorphism of Organic Materials on Surfaces

Jones

Chattopadhyay

Geerts

et al. 2016

Adv Funct Materials

231

280

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2233wileyonlinelibrary.com to that of the bulk liquid; [ 7 ] order typically exists over a few molecular layers before rapidly decaying to bulk behavior as the distance from the wall increases. [ 8 ] Similar ordering effects can also be observed in the quasiliquids which form on the surface of many solids due to surface melting (also known as premelting): [ 9,10 ] the existence of a liquid-like layer a few molecules thick on the surface of a solid below the melting point of the bulk material. [ 11 ] The structure within this layer is also found to be different to that of the bulk isotropic liquid, [ 12 ] highlighting the ordering occurring at the interface. A converse effect, surface freezing, is also observed in some liquids (primarily n -alkanes with 16 ≤ n ≤ 50), where a solid monolayer may exist at an interface up to ≈30 °C above the bulk melting point while the rest of the compound is molten. [13][14][15] Such phase behavior is strongly dependent on molecular shape and has only been observed for chain molecules, which then form layers similar to self-assembled monolayers (SAMs) at the interface with the liquid bulk. [ 16 ] Further examples of molecular ordering at interfaces can be seen in materials which display liquid crystal (LC) phases, a phase behavior also dependent on molecular shape and generally observed for molecules with a highly anisotropic shape (e.g., rod-like, disc-like or bowl-like molecules). [ 17 ] LCs have properties of both solids and liquids and display long range order which may be orientational and/or positional; various types of LC phases (mesophases) are possible and normally exist only over a certain temperature range (i.e., they are thermotropic); a further property of LCs is that they generally reach thermodynamic equilibrium in the bulk and at interfaces as a result of their short relaxation time. Nematic (N) phases of calamitic LCs (rod-like molecules with cylindrical symmetry) have no positional order but an orientational order which can be described by a unit vector, n , known as the director, which represents the preferred molecular orientation ( Figure 1 , left). A scalar order parameter can also be defi ned which is related to the average angle the long molecular axes make to the director, n .Increased order is seen in smetic phases (Sm) which have both orientational and positional order; for example in a smetic A phase (SmA) molecules form layers (positional ordering of the molecular mass centers) which are oriented normal to the plane of the layers (orientational order), while smetic C phases (SmC) form layers where molecules are oriented with the long molecular axes tilted at an angle to the molecular layer normal However, the factors that drive such a process are not clearly understood or studied in depth. In this feature article, we review the current state of understanding concerning SIPs, giving examples of systems where SIPs have been observed, discussing their origins, and which questions remain to be answered. The role of the substrate in controlling the growth a...

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Electrical and Structural Origin of Self‐Healing Phenomena in Pentacene Thin Films

et al. 2017

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Changes of the Molecular Structure in Organic Thin Film Transistors during Operation

Cited by 11 publications

References 45 publications

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

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

Substrate‐Induced and Thin‐Film Phases: Polymorphism of Organic Materials on Surfaces

Electrical and Structural Origin of Self‐Healing Phenomena in Pentacene Thin Films

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