Effect of poly (3-hexylthiophene) film thickness on organic thin film transistor properties

Jia, Haiying; Gowrisanker, Srinivas; Pant, G.; Wallace, Robert M.; Gnade, Bruce E.

doi:10.1116/1.2202858

Cited by 65 publications

(31 citation statements)

References 28 publications

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“…24 The latter is a result of the Poole-Frenkel effect, which is generated by an increase on the planar electric field from source to drain. Charge carrier mobility in these TFTs are comparable to previously reported results, 10,11,25 but the low operating voltage indicates a possibility to function in aqueous media for sensing applications such as medical diagnosis and beverage evaluation by electronic tongues. 8,9 Furthermore, TFTs with microimprinted electrodes may operate at higher frequencies, due to reduced L and higher l, which is necessary for producing potentially competitive low-cost polymeric devices.…”

Section: Thin-film Transistor Performance Analysissupporting

confidence: 77%

Molds and Resists Studies for Nanoimprint Lithography of Electrodes in Low-Voltage Polymer Thin-Film Transistors

Cavallari

Zanchin

Pojar

et al. 2014

Journal of Elec Materi

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A low-cost patterning of electrodes was investigated looking forward to replacing conventional photolithography for the processing of low-operating voltage polymeric thin-film transistors. Hard silicon, etched by sulfur hexafluoride and oxygen gas mixture, and flexible polydimethylsiloxane imprinting molds were studied through atomic force microscopy (AFM) and field emission gun scanning electron microscopy. The higher the concentration of oxygen in reactive ion etching, the lower the etch rate, sidewall angle, and surface roughness. A concentration around 30 % at 100 mTorr, 65 W and 70 sccm was demonstrated as adequate for submicrometric channels, presenting a reduced etch rate of 176 nm/min. Imprinting with positive photoresist AZ1518 was compared to negative SU-8 2002 by optical microscopy and AFM. Conformal results were obtained only with the last resist by hot embossing at 120°C and 1 kgf/cm 2 for 2 min, followed by a 10 min post-baking at 100°C. The patterning procedure was applied to define gold source and drain electrodes on oxide-covered substrates to produce bottom-gate bottom-contact transistors. Poly(3-hexylthiophene) (P3HT) devices were processed on high-j titanium oxynitride (TiO x N y ) deposited by radiofrequency magnetron sputtering over indium tin oxide-covered glass to achieve low-voltage operation. Hole mobility on micrometric imprinted channels may approach amorphous silicon ($0.01 cm 2 /V s) and, since these devices operated at less than 5 V, they are not only suitable for electronic applications but also as sensors in aqueous media.

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Section: Thin-film Transistor Performance Analysissupporting

confidence: 77%

Molds and Resists Studies for Nanoimprint Lithography of Electrodes in Low-Voltage Polymer Thin-Film Transistors

Cavallari

Zanchin

Pojar

et al. 2014

Journal of Elec Materi

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“…Figure 4d shows the field-effect mobilities of the films. The field-effect mobility of the P3HT FET with 0.14 mM HAuCl 4 (3.0 × 10 -2 cm 2 V -1 s -1 ) is about 100-fold greater than that of the pristine P3HT FET (2.8 × 10 -4 cm 2 V -1 s -1 ), which has low field-effect mobilities mainly due to the very low film thickness (∼35 nm), 45 the poor crystallinity and the unfavorable orientation of conjugated plane caused by the fast solvent evaporation rates (CHCl 3 ) of the spin coating method. This increase in the field-effect mobility is probably due to the increase in the molecular ordering of the P3HT chains and their perpendicular orientation with respect to the insulator surface.…”

Section: Resultsmentioning

confidence: 99%

Enhancement of Field-Effect Mobility and Stability of Poly(3-hexylthiophene) Field-Effect Transistors by Conformational Change

et al. 2008

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With the aim of enhancing the field-effect mobility and air stability of self-aligned regioregular poly(3-hexylthiophene), P3HT, by promoting two-dimensional molecular ordering, we transformed the chemical structure of the P3HT chain from a benzoid to a quinoid structure by doping the P3HT solution with HAuCl 4 prior to film formation. We found that, for the appropriate HAuCl 4 concentration, the P3HT nanocrystals adopt a highly ordered molecular structure with a field-effect mobility of 0.03 cm 2 V -1 s -1 , which is an improvement by a factor of more than 100. This increase in field-effect mobility is due to a significant enhancement of molecular ordering and the perpendicular orientation of the nanocrystals with respect to the insulator substrate. This resulted from the change in the P3HT chain conformation from a benzoid to a quinoid structure due to oxidation by HAuCl 4 . The quinoid structure favors a linear or expanded-coil conformation, so the thiophene inter-ring bonds have increased double-bond character, which improves the molecular ordering. Furthermore, the electrical properties of a doped P3HT device had highly improved stability to air without encapsulation. These results suggest that the effect of unintentional doping by oxygen on HAuCl 4 -doped P3HT film is insignificant because the p-type doping effect of HAuCl 4 is the major contributor.

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“…The field-effect mobility of the FET with 0.5 wt % P3HT prepared from a precursor solution with a very small amount of added acetonitrile, 0.8 vol %, (3.6 Â 10 À3 cm 2 V À1 s À1 ) is about 20-fold greater than that of the pristine 0.5 wt % P3HT FET (2.0 Â 10 À4 cm 2 V À1 s À1 ). The value of the field-effect mobility for www.afm-journal.de pristine P3HT is somewhat low, which is mainly due to the very low film thickness ($35 nm), [44] the poor crystallinity, and the unfavorable orientation of the conjugated plane caused by the fast solvent (CHCl 3 ) evaporation rate of the spin coating method. For a high concentration of P3HT (1 wt %), the field-effect mobility of the FET with P3HT prepared from a precursor solution with 3.3 vol % added acetonitrile reaches 1.5 Â 10 À2 cm 2 V À1 s À1 , which is about fivefold greater than that of the pristine 1.0 wt % P3HT FET (3.0 Â 10 À3 cm 2 V À1 s À1 ).…”

Section: Resultsmentioning

confidence: 99%

Solubility‐Induced Ordered Polythiophene Precursors for High‐Performance Organic Thin‐Film Transistors

Park

Lee

Choi

et al. 2009

Adv Funct Materials

220

231

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With the aim of enhancing the field‐effect mobility of self‐assembled regioregular poly(3‐hexylthiophene), P3HT, by promoting two‐dimensional molecular ordering, the organization of the P3HT in precursor solutions is transformed from random‐coil conformation to ordered aggregates by adding small amounts of the non‐solvent acetonitrile to the solutions prior to film formation. The ordering of the precursor in the solutions significantly increases the crystallinity of the P3HT thin films. It is found that with the appropriate acetonitrile concentration in the precursor solution, the resulting P3HT nanocrystals adopt a highly ordered molecular structure with a field‐effect mobility dramatically improved by a factor of approximately 20 depending on the P3HT concentration. This improvement is due to the change in the P3HT organization in the precursor solution from random‐coil conformation to an ordered aggregate structure as a result of the addition of acetonitrile. In the good solvent chloroform, the P3HT molecules are molecularly dissolved and adopt a random‐coil conformation, whereas upon the addition of acetonitrile, which is a non‐solvent for aromatic backbones and alkyl side chains, 1D or 2D aggregation of the P3HT molecules occurs depending on the P3HT concentration. This state minimizes the unfavorable interactions between the poorly soluble P3HT and the acetonitrile solvent, and maximizes the favorable π–π stacking interactions in the precursor solution, which improves the molecular ordering of the resulting P3HT thin film and enhances the field‐effect mobility without post‐treatment.

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Effect of poly (3-hexylthiophene) film thickness on organic thin film transistor properties

Cited by 65 publications

References 28 publications

Molds and Resists Studies for Nanoimprint Lithography of Electrodes in Low-Voltage Polymer Thin-Film Transistors

Molds and Resists Studies for Nanoimprint Lithography of Electrodes in Low-Voltage Polymer Thin-Film Transistors

Enhancement of Field-Effect Mobility and Stability of Poly(3-hexylthiophene) Field-Effect Transistors by Conformational Change

Solubility‐Induced Ordered Polythiophene Precursors for High‐Performance Organic Thin‐Film Transistors

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