Control of charge transport in a semiconducting copolymer by solvent-induced long-range order

Luzio, Alessandro; Criante, Luigino; D’Innocenzo, Valerio; Caironi, Mario

doi:10.1038/srep03425

Cited by 142 publications

(226 citation statements)

References 35 publications

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“…During printing, the inkjet nozzle was rastered from left-right, top-bottom, as looking at the optical micrographs in Figure 2. This is consistent with previous reports of the influence of long range order on charge transport, 20 and semicrystalline face-on p-stacking in P(NDI2OD-T2). 21,22 OFETs were biased in the transdiode regime (V DS ¼ V GS ) and a frequency modulated voltage v GS (f) superimposed on the DC gate bias.…”

supporting

confidence: 93%

Self-aligned organic field-effect transistors on plastic with picofarad overlap capacitances and megahertz operating frequencies

Higgins

Muir

Dell’Erba

et al. 2016

Applied Physics Letters

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Using a combination of nanoimprint lithography, gate-source/drain self-alignment, and gravure and inkjet printing, we fabricate organic field-effect transistors on flexible plastic substrates with gate-source and gate-drain electrode overlap capacitances of COL < 1 pF, equivalent to channel-width normalised capacitances of C*OL = 0.15–0.23 pF mm−1. We compare photopatterned and nanoimprint lithography patterned channels of L ≈ 3.8 μm and L ≈ 800 nm, respectively. The reduction in L was found on average to result in order of magnitude greater switching frequencies. Gravure printing the dielectric (versus photo-patterning) was found to yield an order of magnitude lower overlap capacitance C*OL = 0.03 pF mm−1, at the expense of greater processing variation. Inkjet printed p- and n-type polymeric organic semiconductors were used to fabricate organic-field effect transistors with a peak cutoff frequencies of fS = 9.0 ± 0.3 MHz at VGS = 30 V, and transition frequencies of fT = 3.3 ± 0.2 MHz at VGS = 30 V.

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supporting

confidence: 93%

Self-aligned organic field-effect transistors on plastic with picofarad overlap capacitances and megahertz operating frequencies

Higgins

Muir

Dell’Erba

et al. 2016

Applied Physics Letters

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“…[ 36 ] In this work we propose an easy and general method for the assessment of the injection length in staggered OTFTs and we apply it to poly{[ N , N ′-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′-bithiophene)} (P(NDI2OD-T2)), a printable, prototypical n-type polymer with a high mobility, exceeding 1 cm 2 V −1 s −1 when processed from suitable pre-aggregating solvents. [ 11,37 ] Interestingly enough we fi nd that in P(NDI2OD-T2) the injection length scales with the channel length when applied voltages are kept constant, resulting in a much more favorable downscaling than expected. Our methodology allows to rationalize and to generalize this result, which is valid for all staggered transistors where the electrode-semiconductor injection process is dominating over the semiconductor bulk contribution.…”

Section: Introductionmentioning

confidence: 70%

Injection Length in Staggered Organic Thin Film Transistors: Assessment and Implications for Device Downscaling

Natali

Chen

Maddalena

et al. 2016

Adv Elect Materials

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of organic semiconductors show carrier mobility in excess of 5 cm 2 V −1 s −1 when employed as active materials in long (>10 μm) channel organic thin fi lm transistors (OTFT). [2][3][4][5][6][7][8][9][10][11][12] Therefore by scaling the channel length down to 10-1 μm, in principle OTFTs should be able to operate at relatively high (1-10 MHz) frequencies at reasonable (<10 V) applied voltages. [ 13 ] In practice, apart from some reports, [13][14][15][16][17][18][19][20][21][22] this is often not easy to achieve because of injection issues: [ 23,24 ] contact resistances tend to become dominant over the channel resistance in short channel transistors reducing the expected improvement of device performances. [ 25 ] This situation is severely limiting the range of applications for OTFTs. [ 26 ] Indeed contact resistances arise from contact/semiconductor interface properties hence they are not expected to scale with the transistor channel length. To address this issue not only suitable modifi cations of the contact/semiconductor interface aimed at enhancing the contact injecting properties have to be implemented, [ 27 ] but also the device topology has to be considered. Staggered OTFTs, where the contacts and the transistor channel do not lie in the same plane, are usually characterized by lower contact resistances than coplanar ones: [ 28 ] while in these latter the injection area is limited by the accumulated channel depth (few nanometers), in the former the overlap between gate and source/drain contacts (many micrometers or even tens of micrometers) can be exploited, as shown in Figure 1 . The gate/contact overlapping length has to be suitably engineered: on the one hand it should be large enough to accommodate the injected current and to minimize contact resistances; but on the other hand it should not be too large because overlapping areas not effectively involved in injection solely result in additional parasitic capacitances that deteriorate the device speed. [ 13,29 ] It is therefore important to quantify the injection length, which is the length over which sizeable carrier injection occurs. [ 30,31 ] Despite the large number of studies on contact effects in OTFTs, [ 24,32 ] few of them discuss the effect of the gate to contact overlap: Xu et al. found a relationship between the optimal contact length and the semiconductor thickness in staggered OTFT. [ 33 ] Park et al. found that threshold voltage, fi eld effect mobility and contact resistances are affected by the contact length in staggered OTFT; [ 34 ] Wang et al. simulated the effect of contact length scaling. [ 35 ] Ante et al. studied the effect of contact In staggered thin fi lm transistors, the injection length is the fraction of the gate to contact overlap that is effectively involved in current injection. Its assessment is important to properly downscale device dimensions. In fact, in order to increase transistor operation speed, the whole device footprint should be downscaled, which means both the gate to contact overlap and the channel length, as ...

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“…[72] Moreover, charge transport in organic semiconductors not only depends on features like crystallinity, but, especially in films with a consistent amorphous-like phase, important factors are also film interconnectivity [1,78] and degree of noncrystalline orientational order, [79] as recently evidenced for example for PNDI2OD-T2. [3,80] Therefore, typical bulk average structural characterization of the ordered phase, as obtained by GIWAXS, has to be completed with more specific, channel sensitive investigations. For the PNDI-SVS copolymer investigated in this work, AFM surface analysis and surface-sensitive NEXAFS reveal that the packing motif at the surface of the film is prevalently edge-on, compared to the prevalently faceon packing of the bulk.…”

Section: Polarized Charge Modulation Microscopymentioning

confidence: 99%

High‐Mobility Naphthalene Diimide and Selenophene‐Vinylene‐Selenophene‐Based Conjugated Polymer: n‐Channel Organic Field‐Effect Transistors and Structure–Property Relationship

Sung

Luzio

Park

et al. 2016

Adv Funct Materials

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Interdependence of chemical structure, thin-film morphology, and transport properties is a key, yet often elusive aspect characterizing the design and development of high-mobility, solution-processed polymers for large-area and flexible electronics applications. There is a specific need to achieve >1 cm 2 V −1 s −1 field-effect mobilities (μ) at low processing temperatures in combination with environmental stability, especially in the case of electron-transporting polymers, which are still lagging behind hole transporting materials. Here, the synthesis of a naphthalene-diimide based donor-acceptor copolymer characterized by a selenophene vinylene selenophene donor moiety is reported. Optimized field-effect transistors show maximum μ of 2.4 cm 2 V −1 s −1 and promising ambient stability. A very marked film structural evolution is revealed with increasing annealing temperature, with evidence of a remarkable 3D crystallinity above 180 °C. Conversely, transport properties are found to be substantially optimized at 150 °C, with limited gain at higher temperature. This discrepancy is rationalized by the presence of a surface-segregated prevalently edge-on packed polymer phase, dominating the device accumulated channel. This study therefore serves the purpose of presenting a promising, high-electron-mobility copolymer that is processable at relatively low temperatures, and of clearly highlighting the necessity of specifically investigating channel morphology in assessing the structure-property nexus in semiconducting polymer thin films.

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Control of charge transport in a semiconducting copolymer by solvent-induced long-range order

Cited by 142 publications

References 35 publications

Self-aligned organic field-effect transistors on plastic with picofarad overlap capacitances and megahertz operating frequencies

Self-aligned organic field-effect transistors on plastic with picofarad overlap capacitances and megahertz operating frequencies

Injection Length in Staggered Organic Thin Film Transistors: Assessment and Implications for Device Downscaling

High‐Mobility Naphthalene Diimide and Selenophene‐Vinylene‐Selenophene‐Based Conjugated Polymer: n‐Channel Organic Field‐Effect Transistors and Structure–Property Relationship

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