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On the mode of operation in electrolyte-gated thin film transistors based on different substituted polythiophenes
Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
University of Paris Diderot, France .
University of Paris Diderot, France .
Ecole Polytechnique, Palaiseau, France.
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2014 (English)In: Organic electronics, ISSN 1566-1199, Vol. 15, no 10, 2420-2427 p.Article in journal (Refereed) Published
Abstract [en]

Organic Thin Film Transistors (OTFT), gated through an aqueous electrolyte, have extensively been studied as sensors in various applications. These water-gated devices are known to work both as electrochemical (Organic ElectroChemical Transistor - OECT) and field-effect (Organic Field-Effect Transistor - OFET) devices. To properly model and predict the response of water-gated OTFT sensors it is important to distinguish between the mechanism, field-effect or electrochemical, by which the transistor is modulated and thus how the gate signal can be affected by the analyte. In this present study we explore three organic polymer semiconductors, poly-(3-hexyl-thiophene) (P3HT), poly-(3-carboxypentyl-thiphene) (P3CPT) and a co-polymer P3HT-co-poly-(3-ethoxypentanoic acid-thiophene) (monomer ratio 1:6, P3HT-COOH15) in water-gated OTFT structures. We report a set of transistor characteristics, including standard output parameters, impedance spectroscopy and current transients, to investigate the origin of the mode of operation in these water-gated OTFTs. Impedance characteristics, including both frequency and voltage dependence, were recorded for capacitor stacks corresponding to the gate/electrolyte/semiconductor/source structure. It is shown that P3HT as well as P3HT-COOH15 both can function as semiconductors in water gated OTFT devices operating in field-effect mode. P3CPT on the other hand shows typical signs of electrochemical mode of operation. The -COOH side group has been suggested as a possible anchoring site for biorecognition elements in EGOFET sensors, rendering P3HT-COOH15 a possible candidate for such applications.

Place, publisher, year, edition, pages
Elsevier, 2014. Vol. 15, no 10, 2420-2427 p.
Keyword [en]
Sensor; OTFT; Transistor; Electrolyte; EGOFET
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
URN: urn:nbn:se:liu:diva-110957DOI: 10.1016/j.orgel.2014.06.017ISI: 000341290000035OAI: diva2:752285

Funding Agencies|European Union [248728]; Swedish Government (SFO-AFM); Onnersjo Foundation (Holmen); Knut and Alice Wallenberg Foundation (Power Papers); VINNOVA (PEA)

Available from: 2014-10-03 Created: 2014-10-01 Last updated: 2015-10-07Bibliographically approved
In thesis
1. Operating Organic Electronics via Aqueous Electric Double Layers
Open this publication in new window or tab >>Operating Organic Electronics via Aqueous Electric Double Layers
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The field of organic electronics emerged in the 1970s with the discovery of conducting polymers. With the introduction of plastics as conductors and semiconductors came many new possibilities both in production and function of electronic devices. Polymers can often be processed from solution and their softness provides both the possibility of working on flexible substrates, and various advantages in interfacing with other soft materials, e.g. biological samples and specimens. Conducting polymers readily partake in chemical and electrochemical reactions, providing an opportunity to develop new electrochemicallydriven devices, but also posing new problems for device engineers.

The work of this thesis has focused on organic electronic devices in which aqueous electrolytes are an active component, but still operating in conditions where it is desirable to avoid electrochemical reactions. Interfacing with aqueous electrolytes occurs in a wide variety of settings, but we have specifically had biological environments in mind as they necessarily involve the presence of water. The use of liquid electrolytes also provides the opportunity to deliver and change the device electrolyte continuously, e.g. through microfluidic systems, which could then be used as a dynamic feature and/or be used to introduce and change analytes for sensors. Of particular interest is the electric double layer at the interface between the electrolyte and other materials in the device,  specifically its sensitivity to charge reorganization and high capacitance.

The thesis first focuses on organic field effect transistors gated through aqueous electrolytes. These devices are proposed as biosensors with the transistor architecture providing a direct transduction and amplification so that it can be electrically read out. It is discussed both how to distinguish between the various operating mechanisms in electrolyte thin film transistors and how to choose a strategy to achieve the desired mechanism. Two different strategies to suppress ion penetration into, and thus electrochemical doping of, the organic semiconductor are presented.

The second focus of the thesis is on polarization of ferroelectric polymer films through electrolytes. A model for the interaction between the remnant ferroelectric charge in the polymer film and the mobile ionic charges of the electrolyte is presented, and verified experimentally. The reorientation of the ferroelectric polarization via the electric double layer is also demonstrated in a regenerative medicine application; the ferroelectric polarization is shown to affect cell binding, and is used as a gentle method to nondestructively detach cells from a culture substrate.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2015. 61 p.
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1704
National Category
Physical Sciences Electrical Engineering, Electronic Engineering, Information Engineering
urn:nbn:se:liu:diva-121805 (URN)10.3384/diss.diva-121805 (DOI)978-91-7685-944-5 (print) (ISBN)
Public defence
2015-11-09, K3, Kåkenhus, Campus Norrköping, Norrköping, 14:00
Available from: 2015-10-07 Created: 2015-10-07 Last updated: 2015-10-12Bibliographically approved

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