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Light-Emitting Electrochemical Transistors
Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Since the discovery of conductive polymers in 1977, the implementation of organic conjugated materials in electronic applications has been of great interest in both industry and academia. The goal of organic electronics is to realize large-area, inexpensive and mechanically-flexible electronic applications.

Organic light emitting diodes (OLEDs), as the first commercial product made from organic conjugated polymers, have successfully demonstrated that organic electronics can make possible a new generation of modern electronics. However, OLEDs are highly sensitive to materials selection and requires a complicated fabrication process. As a result, OLEDs are expensive to fabricate and are not suitable for low-cost printing or roll-to-roll process.

This thesis studies an alternative to OLEDs: light-emitting electrochemical cells (LECs). The active materials in an LEC consist of a conjugated light-emitting polymer (LEP) and an electrolyte. Taking advantage of electrochemical doping of the LEP, an LEC features an in-situ formed emissive organic p-n junction which is easy to fabricate. We aim to control the electrochemical doping profile by employing a “gate” terminal on top of a conventional LEC, forming a lightemitting electrochemical transistor (LECT). We developed three generations of LECTs, in which the position of the light-emitting profile can be modified by the voltage applied at the gate electrode, as well as the geometry of the gate materials. Thus, one can use this structure to achieve a centered light-emitting zone to maximize the power-conversion efficiency. Alternatively, LECTs can be used for information display in a highly integrated system, as it combines the simultaneous modulation of photons and electrons.

In addition, we use multiple LECs to construct reconfigurable circuits, based on the reversible electrochemical doping. We demonstrate an LEC-array where several different circuits can be created by forming diodes with different polarity at different locations. The thereby formed circuitry can be erased and turned into circuitry with other functionality. For example, the diodes of a digital AND gate can be re-programmed to form an analogue voltage limiter. These reprogrammable circuits are promising for fully-printed and large-area reconfigurable circuits with facile fabrication.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2014. , 57 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1582
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:liu:diva-104925DOI: 10.3384/diss.diva-104925ISBN: 978-91-7519-382-3 (print)OAI: oai:DiVA.org:liu-104925DiVA: diva2:700134
Public defence
2014-03-21, K2, Kåkenhus, Campus Norrköping, Linköpings universitet, Norrköping, 10:15 (English)
Opponent
Supervisors
Available from: 2014-03-03 Created: 2014-03-03 Last updated: 2017-02-03Bibliographically approved
List of papers
1. Vertical polyelectrolyte-gated organic field-effect transistors
Open this publication in new window or tab >>Vertical polyelectrolyte-gated organic field-effect transistors
Show others...
2010 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 97, 103303- p.Article in journal (Refereed) Published
Abstract [en]

Short-channel, vertically structured organic transistors with a polyelectrolyte as gate insulator are demonstrated. The devices are fabricated using low-resolution, self-aligned, and mask-free photolithography. Owing to the use of a polyelectrolyte, our vertical electrolyte-gated organic field-effect transistors (VEGOFETs), with channel lengths of 2.2 and 0.7 μm, operate at voltages below one volt. The VEGOFETs show clear saturation and switch on and off in 200 μs. A vertical geometry to achieve short-transistor channels and the use of an electrolyte makes these transistors promising candidates for printed logics and drivers with low operating voltage.

Place, publisher, year, edition, pages
American Institute of Physics, 2010
Keyword
organic field effect transistors, organic semiconductors, photolithography, polymer electrolytes
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-59578 (URN)10.1063/1.3488000 (DOI)000282478800049 ()
Note
Original Publication: Jiang Liu, Lars Herlogsson, A Sawadtee, P Favia, M Sandberg, Xavier Crispin, Isak Engquist and Magnus Berggren, Vertical polyelectrolyte-gated organic field-effect transistors, 2010, Applied Physics Letters, (97), , 103303. http://dx.doi.org/10.1063/1.3488000 Copyright: American Institute of Physics http://www.aip.org/ Available from: 2010-09-21 Created: 2010-09-21 Last updated: 2017-12-12
2. Organic Reprogrammable Circuits Based on Electrochemically-Formed Diodes
Open this publication in new window or tab >>Organic Reprogrammable Circuits Based on Electrochemically-Formed Diodes
2014 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 6, no 15, 13266-13270 p.Article in journal (Refereed) Published
Abstract [en]

To simplify the integration of organic electronics, we demonstrate a method for constructing reprogrammable circuits based on organic diodes. The organic p‐n junction diodes consisting of an organic polymers poly[2‐methoxy‐5‐(2‐ethylhexyloxy)‐1,4‐phenylenevinylene and an electrolyte were formed by electrochemical doping at 70 °C, and stabilized at ‐30 °C. The reversible electrochemical reaction allows for the in‐situ change of the polarity of the organic p‐n junction. By forming diodes with different polarity at different locations, several circuits can be created, such as, logic gates, voltage limiter and AC/DC converter. The as‐made circuitry can be erased and turned into circuitry with other functionality. For example, the diodes of an AND gate can be re‐programmed to form an OR gate. The reprogrammable circuits contain merely two core layers, electrodes and active material, which is promising for large‐area and fully‐printed reconfigurable circuits with facile fabrication.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2014
Keyword
organic reprogrammable circuit; light-emitting electrochemical cell; electrochemistry; organic diode; MEH-PPV; polymer electrolyte
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:liu:diva-104923 (URN)10.1021/am503129b (DOI)000340446300170 ()
Available from: 2014-03-03 Created: 2014-03-03 Last updated: 2017-12-05
3. Spatial Control of p-n Junction in an Organic Light-Emitting Electrochemical Transistor
Open this publication in new window or tab >>Spatial Control of p-n Junction in an Organic Light-Emitting Electrochemical Transistor
2012 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 134, no 2, 901-904 p.Article in journal (Refereed) Published
Abstract [en]

Low-voltage-operating organic electrochemical light-emitting cells (LECs) and transistors (OECTs) can be realized in robust device architectures, thus enabling easy manufacturing of light sources using printing tools. In an LEC, the p-n junction, located within the organic semiconductor channel, constitutes the active light-emitting element. It is established and fixated through electrochemical p- and n-doping, which are governed by charge injection from the anode and cathode, respectively. In an OECT, the electrochemical doping level along the organic semiconducting channel is controlled via the gate electrode. Here we report the merger of these two devices: the light-emitting electrochemical transistor, in which the location of the emitting p-n junction and the current level between the anode and cathode are modulated via a gate electrode. Light emission occurs at 4 V, and the emission zone can be repeatedly moved back and forth within an interelectrode gap of 500 mu m by application of a 4 V gate bias. In transistor operation, the estimated on/off ratio ranges from 10 to 100 with a gate threshold voltage of -2.3 V and transconductance value between 1.4 and 3 mu S. This device structure opens for new experiments tunable light sources and LECs with added electronic functionality.

Place, publisher, year, edition, pages
American Chemical Society, 2012
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-76542 (URN)10.1021/ja210936n (DOI)000301084300041 ()
Note
Funding Agencies|Swedish Government||Swedish Foundation for Strategic Research (OPEN)||VINNOVA (PEA-PPP)||Tillvaxtverket||Knut and Alice Wallenberg Foundation||Onnesjo Foundation||Available from: 2012-04-12 Created: 2012-04-11 Last updated: 2017-12-07
4. Double-Gate Light-Emitting Electrochemical Transistor: Confining the Organic p-n Junction
Open this publication in new window or tab >>Double-Gate Light-Emitting Electrochemical Transistor: Confining the Organic p-n Junction
2013 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 135, no 33, 12224-12227 p.Article in journal (Refereed) Published
Abstract [en]

In conventional light-emitting electrochemical cells (LECs), an off-centered p-n junction is one of the major drawbacks, as it leads to exciton quenching at one of the charge-injecting electrodes and results in performance instability. To combat this problem, we have developed a new device configuration, the double-gate light-emitting electrochemical transistor (DG-LECT), in which the location of the light-emitting p-n junction can be precisely defined via the position of the two gate terminals. Based on a planar LEC structure, two gate electrodes made from an electrochemically active conducting polymer are employed to predefine the p- and n-doped area of the light-emitting polymer. Thus, a p-n junction is formed in between the p-doped and n-doped regions. We demonstrate a homogeneous and centered p-n junction as well as other predefined junction patterns in these DG-LECT devices. Additionally, we report an electrical model that explains the operation of the DG-LECTs. The DG-LECT device provides a new tool to study the fundamental physics of LECs, as it dissects the key working process of LEC into decoupled p-doping, n-doping, and electroluminescence.

Place, publisher, year, edition, pages
American Chemical Society, 2013
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-97661 (URN)10.1021/ja407049b (DOI)000323536100019 ()
Note

Funding Agencies|Swedish Foundation for Strategic Research (OPEN)||European Regional Development Fund through Tillvaxtverket (PEA-PPP)||VINNOVA|2012-01607|Knut and Alice Wallenberg Foundation||Onnesjo Foundation||

Available from: 2013-09-19 Created: 2013-09-19 Last updated: 2017-12-06
5. Half‐Gate Light‐Emitting Electrochemical Transistor to Achieve Centered Emissive Organic p‐n Junction
Open this publication in new window or tab >>Half‐Gate Light‐Emitting Electrochemical Transistor to Achieve Centered Emissive Organic p‐n Junction
2014 (English)In: Organic electronics, ISSN 1566-1199, E-ISSN 1878-5530, Vol. 18, 32-36 p.Article in journal (Refereed) Published
Abstract [en]

Conventional organic light-emitting electrochemical cells show promise for lighting applications but in many cases suffer from unbalanced electrochemical doping. A predominant p-doping over n-doping causes an off-centered emissive p-n junction, which leads to poor power-conversion efficiency. Here, we report a half-gate lightemitting electrochemical transistor (HGLECT), in which a ion-conductive gate made from poly(3,4-ethylenedioxythiophene)-poly-(styrenesulfonate) is employed to combat this problem. The gate material, covering half the channel, is used to enhance the ndoping in this part by employing an appropriate operation protocol. We demonstrate a centered light emission zone, closely following the geometry of the gate material. The HGLECT with centered emission profile is shown to be more efficient than the corresponding LEC without gate electrode, and its n-doping level is measured to be 15%.

Place, publisher, year, edition, pages
Elsevier, 2014
Keyword
Light-emitting electrochemical transistor; Light-emitting electrochemical cell; PEDOT:PSS; MEH-PPV; Polymer electrolyte
National Category
Physical Sciences Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:liu:diva-104924 (URN)10.1016/j.orgel.2014.12.027 (DOI)000349548400005 ()
Note

On the day of the defence date the status of this article was Manuscript.

Available from: 2014-03-03 Created: 2014-03-03 Last updated: 2017-12-05Bibliographically approved

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