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Electrochemical and electronic devices based on low bandgap polymers
Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The research field of the organic electronics includes light emitting diodes (OLEDs), field-effect transistors (OFETs), polymer photovoltaic cells (PVCs), polymer lasers and electrochemical devices. Recently, organic materials are envisaged for spintronics. This dissertation covers a large research scope ranging from electrochemical devices, light emitting diodes, to field-effect transistors, in both processing techniques and device characterizations.

Printed all-organic electrochemical diodes and transistors on flexible plastic or paper substrates have been realized by simple and low-cost method of fabricating. Conducting polymer poly(3,4-ethylenedioxythiophene) poly(styrene sulfonate) (PEDOT:PSS), utilized as active component, is deposited by spin-coating or printing techniques. The devices are directly fabricated from design without the need for masks, patterns or dies. The output characteristics of both half-wave and full-wave rectifier circuits from two-terminal diodes show stable performances at frequencies of 5 Hz. Electrochemical transistors based on both three- and four-terminal configurations have good performances with IONlIoFF current ratios of 103 - 104 at operating voltages below 3 V. The new kind of devices reported are robust and could serve as components in microelectronics, and as redox sensors and detectors since the conductivity of conducting polymers depends on the redox states.

Both LEDs and FETs are realized from a low bandgap donor-acceptor-donor (D-A-D) polymer. The polymer consists of fluorene units and donor-acceptor-donor (D-A-D) units. The D-A-D segment includes two electron-donating thiophene rings combined with a thiadiazolo-quinoxaline unit, which is electron withdrawing to its nature. The resulting polymer is conjugated and has a band gap of 1.27 eV. The corresponding electro- and photoluminescence spectra both peak at approximately 1 Ilm, which is largest emission wavelength ever reported to date. The resulting FETs exhibit typical p-channel functions, and relatively high field-effect mobility of 0.03 cm2y-1s-1, near zero threshold voltage and a current on/off ratio of 5 x104 in ambient atmosphere. The mobility value is highest in low bandgap D-A-D polymers ever reported so far.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press , 2005. , 79 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 916
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-38775Local ID: 45585ISBN: 91-85297-09-7 (print)OAI: oai:DiVA.org:liu-38775DiVA: diva2:259624
Public defence
2005-05-12, K3, Kåkenhus, Campus Norrköping, Linköpings universitet, Norrköping, 10:00 (English)
Opponent
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2012-12-07Bibliographically approved
List of papers
1. Bi-stable and dynamic current modulation in electrochemical organic transistors
Open this publication in new window or tab >>Bi-stable and dynamic current modulation in electrochemical organic transistors
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2002 (English)In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 14, no 1, 51-54 p.Article in journal (Refereed) Published
Abstract [en]

Novel electrochemical transistors, based on the conductive polymer PEDOT, operating at driving voltages of only a few volts in bulk material, and with little demand on substrate planarity, are described by the authors. The underlying polymer ion pair PEDOT:PSS is conductive in both oxidized and reduced state. Two transistor architectures, a bi-stable and a dynamic transistor (the first electrochemical specimen of its kind) with an on/off ratio of 105 and 200 Hz modulation speed, were realized.

Keyword
Conductivity, Polymer films, Transistors
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-13560 (URN)10.1002/1521-4095(20020104)14:1<51::AID-ADMA51>3.0.CO;2-# (DOI)
Available from: 2008-11-12 Created: 2008-11-12 Last updated: 2017-02-03
2. Electric current rectification by an all-organic electrochemical device
Open this publication in new window or tab >>Electric current rectification by an all-organic electrochemical device
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2002 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 81, 2011-2013 p.Article in journal (Refereed) Published
Abstract [en]

An all-organic printed electrochemical rectifier is reported. The device is based on a patterned layer of poly(3,4-ethylenedioxythiophene) poly(styrene sulfonate) (PEDOT:PSS) that interfaces a patterned electrolyte top layer. Overlap between the electrolyte layer and the conducting polymer pattern results in the formation of two electrochemically active areas within the conducting polymer pattern. When bias voltage is applied across the conducting polymer pattern, the PEDOT in the negatively biased areas is reduced electrochemically, while the PEDOT in the positively biased area is further oxidized. Reducing PEDOT from its p-doped, pristine state to the neutral state results in a marked loss of electrical conductivity. Due to the unsymmetrical device geometry, the current through the device may be shut off for one polarity of applied bias voltage with an electrical current rectification ratio of 100 compared to the opposite polarity. The output characteristics of a corresponding half wave rectifier as well as those from a full wave bridge rectifier show stable performance at frequencies below 15 Hz.

Keyword
rectification; conducting polymers; electrolytes; electrochemical devices; oxidation; organic semiconductors; semiconductor-electrolyte boundaries
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-32681 (URN)10.1063/1.1506785 (DOI)18601 (Local ID)18601 (Archive number)18601 (OAI)
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2017-12-13
3. 1 micron wavelength photo- and electroluminescence from a conjugated polymer
Open this publication in new window or tab >>1 micron wavelength photo- and electroluminescence from a conjugated polymer
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2004 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 84, no 18, 3570-3572 p.Article in journal (Refereed) Published
Abstract [en]

We report photo- and electroluminescence from an alternating conjugated polymer consisting of fluorene units and low-band gap donor-acceptor-donor (D–A–D) units. The D–A–D segment includes two electron-donating thiophene rings combined with a thiadiazolo-quinoxaline unit, which is electron withdrawing to its nature. The resulting polymer is conjugated and has a band gap of 1.27 eV. The corresponding electro- and photoluminescence spectra both peak at approximately 1 μm. Light-emitting diodes, based on a single layer of the polymer, demonstrated external quantum efficiencies from 0.03% to 0.05%.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-22529 (URN)10.1063/1.1737064 (DOI)1790 (Local ID)1790 (Archive number)1790 (OAI)
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2017-02-03
4. Low band gap donor–acceptor–donor polymers for infra-red electroluminescence and transistors
Open this publication in new window or tab >>Low band gap donor–acceptor–donor polymers for infra-red electroluminescence and transistors
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2004 (English)In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 146, no 3, 233-236 p.Article in journal (Refereed) Published
Abstract [en]

We report on transistors and light-emitting diodes using a conjugated polymer consisting of alternated segments of fluorene units and low-band gap donor–acceptor–donor (D–A–D) units. The D–A–D segment includes two electron-donating thiophene rings combined with a thiadiazolo-quinoxaline unit, which is electron withdrawing to its nature. The resulting polymer is conjugated and has a band gap of around 1.27 eV. Here we present the corresponding electro- and photoluminescence spectra, which both peak at approximately 1 μm. Single layer light-emitting diodes demonstrated external quantum efficiencies from 0.03% to 0.05%. The polymer was employed as active material in thin film transistors, a field-effect mobility of 3 × 10−3 cm2/V s and current on/off ratio of 104 were achieved at ambient atmosphere.

Keyword
polymers, infra-red electroluminescence, band gap
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-46161 (URN)10.1016/j.synthmet.2004.08.002 (DOI)
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-13
5. High carrier mobility in low band gap polymer-based field-effect transistors
Open this publication in new window or tab >>High carrier mobility in low band gap polymer-based field-effect transistors
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2005 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 87, no 25, 252105-1-252105-3 p.Article in journal (Refereed) Published
Abstract [en]

A conjugated polymer with a low band gap of 1.21 eV, i.e., absorbing infrared light, is demonstrated as active material in field-effect transistors (FETs). The material consists of alternating fluorene units and low band gap segments with electron donor-acceptor-donor units composed of two electron-donating thiophene rings attached on both sides of a thiadiazolo-quinoxaline electron-acceptor group. The polymer is solution-processable and air-stable; the resulting FETs exhibit typical p-channel characteristics and field-effect mobility of 0.03 cm2 V−1 s−1.

National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-34581 (URN)10.1063/1.2142289 (DOI)22029 (Local ID)22029 (Archive number)22029 (OAI)
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-12-13

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