liu.seSearch for publications in DiVA
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Optimization of the thermoelectric figure of merit in the conducting polymer poly(3,4-ethylenedioxythiophene)
Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
Show others and affiliations
2011 (English)In: NATURE MATERIALS, ISSN 1476-1122, Vol. 10, no 6, 429-433 p.Article in journal (Refereed) Published
Abstract [en]

Thermoelectric generators (TEGs) transform a heat flow into electricity. Thermoelectric materials are being investigated for electricity production from waste heat (co-generation) and natural heat sources. For temperatures below 200 degrees C, the best commercially available inorganic semiconductors are bismuth telluride (Bi2Te3)-based alloys, which possess a figure of merit ZT close to one(1). Most of the recently discovered thermoelectric materials with ZT andgt; 2 exhibit one common property, namely their low lattice thermal conductivities(2,3). Nevertheless, a high ZT value is not enough to create a viable technology platform for energy harvesting. To generate electricity from large volumes of warm fluids, heat exchangers must be functionalized with TEGs. This requires thermoelectric materials that are readily synthesized, air stable, environmentally friendly and solution processable to create patterns on large areas. Here we show that conducting polymers might be capable of meeting these demands. The accurate control of the oxidation level in poly(3,4-ethylenedioxythiophene) (PEDOT) combined with its low intrinsic thermal conductivity (lambda = D 0.37W m(-1) K-1) yields a ZT = 0.25 at room temperature that approaches the values required for efficient devices.

Place, publisher, year, edition, pages
Nature Publishing Group , 2011. Vol. 10, no 6, 429-433 p.
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-68783DOI: 10.1038/nmat3012ISI: 000290855100016OAI: oai:DiVA.org:liu-68783DiVA: diva2:421193
Available from: 2011-06-08 Created: 2011-06-07 Last updated: 2017-02-03
In thesis
1. Thermoelectric properties of conducting polymers
Open this publication in new window or tab >>Thermoelectric properties of conducting polymers
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

According to different sources, from forty to sixty percent of the overall energy generated in the world today is squandered in waste heat. The existing energy conversion technologies are either close to their efficiency limits or too costly to justify their implementation. Therefore, the development of new technological approaches for waste heat recovery is highly demanded. The field of thermoelectrics can potentially provide an inexpensive, clean and efficient solution to waste heat underutilization, given that a new type of thermoelectric materials capable of meeting those requirements are available.

This thesis reports on strategies to optimize a thermoelectric efficiency (ZT) of conducting polymers, more specifically poly(3,4-ethylenedioxythiophene) (Pedot). Conducting polymers constitute a special class of semiconductors characterized by low thermal conductivity as well as electrical conductivity and thermopower that can be readily modified by doping in order to achieve the best combination of thermoelectric parameters. Conducting polymers that have never previously been regarded as hypothetically compatible for thermoelectric energy conversion, can exhibit promising thermoelectric performance at moderate temperatures, which is a sought-after quality for waste heat recovery. A rather substandard thermoelectric efficiency of Pedot-Pss can be markedly improved by various secondary dopants whose addition usually improves polymer’s morphology accompanied by a drastic increase in electrical conductivity and, consequently, in ZT. In order to enable further enhancement in thermoelectric properties, the optimization of the charge carrier concentration is commonly used. The oxidation level of Pedot-Pss can be precisely controlled by electrochemical doping resulting in a tenfold increase of ZT. In contrast to Pedot-Pss, another conducting polymer Pedot-Tos exhibits superior thermoelectric performance even without secondary doping owning to its partially crystalline nature that allows for an improved electronic conduction. With the aid of a strong electron donor, positively doped Pedot-Tos gets partially reduced reaching the optimum oxidation state at which its thermoelectric efficiency is just four times smaller than that of Be2Te3 and the highest among all stable conducting polymers. The downsides associated with chemical doping of Pedot-Tos such as doping inhomogeneity or chemical dopants air sensitivity can be surmounted if the doping level of Pedot-Tos is controlled by acidity/basicity of the polymer. This approach yields similar maximum thermoelectric efficiency but does not necessitate inert conditions for sample preparation. Optimized Pedot-Tos/Pedot-Pss can be functionalized as a p-type material in organic thermogenerators (OTEG) to power low energy electronic devices. If printed on large areas, OTEGs could be used as an alternative technique for capturing heat discarded by industrial processes, households, transportation sector or any natural heat sources for electricity production.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2013. 53 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1491
Keyword
Thermoelectric generation, Seebeck coefficient, conducting polymers, thermoelectric efficiency.
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-87476 (URN)978-91-7519-741-8 (ISBN)
Public defence
2013-01-25, K3, Kåkenhus, Campus Norrköping, Linköpings universitet, Norrköping, 10:15 (English)
Opponent
Supervisors
Available from: 2013-01-18 Created: 2013-01-18 Last updated: 2017-02-03Bibliographically approved
2. Thermoelectric Devices with Electronic and Ionic Conducting Polymers
Open this publication in new window or tab >>Thermoelectric Devices with Electronic and Ionic Conducting Polymers
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The energy consumption in the world is continuously growing and the sources of energy are largely dominated by fossil fuels. However, the resources of oil, gas and coal are diminishing in capacity. Moreover the CO2 emissions arising from their combustion is a great concern because it induces climate changes that threaten our habitat. There is a dire need to look for alternative sources of energies and to minimize losses of energy in our surroundings. Heat engines and turbines typically running with fossil energy have efficiencies of about 35%, i.e. 65% of the energy is lost in the form of heat. Low temperature heat (<200 C) is almost always wasted in power plants, industries, automobiles and household appliances. This is a huge resource that can be directly converted to electricity through the concept of thermoelectricity. Major challenges for heat to electricity conversion include finding the abundant materials with efficient thermoelectric (TE) conversion that can be mass produced at low cost.

This thesis presents an investigation of the TE properties of electronic and ionic conducting polymers, as well as their implementation in thermoelectric devices. This is a journey from thin solid films on a substrate to wet and liquid media and towards bulk structures utilizing the same core concept of thermoelectricity. The TE device concepts introduced here are suitable for various heat sources i.e. continuous, intermittent and instantaneous. The thesis has three major parts as follows:

Conducting polymers (CPs) have been studied mainly as thin films. They have been synthesized in different ways and their properties have been compared to propose the most efficient amongst them for thermoelectricity. Simple methods of exposure to certain gases or liquids have been used to tune their TE properties and demonstrated its applications in thermoelectric generator (TEGs).

Ionic materials have also been studied as potential candidates for thermoelectricity. Polyelectrolytes constitute a special class of electrolytes with dissimilar sizes of ions; a polymeric ion and a small counter ion. The movement of the small sodium (Na+) cation under heat gradient was explored in wet films and in solution. Because the ions could not cross the electrolyte-electrode junction, we propose the idea of ionic thermoelectric supercapacitor (ITESC), suitable for intermittent heat source.

Nanofibrillated cellulose (NFC) has been used along with conducting polymers to realize the three dimensional conducting bulks as a TEG leg. NFC bulks were coated with conducting polymers as a first approach and later the mixture of (NFC & CP) was freeze-dried. The later approach resulted in mechanically flexible structures that were used as dual sensors for pressure and temperature based on the TE properties of the CP which can be utilized for electronic skin applications.

The thesis shows new ways of utilizing waste heat using polymeric materials and points to a sensory application area, broadening the horizons of thermoelectricity.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2015. 50 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1709
Keyword
Thermoelectricity, conducting polymers, thermoelectric devices
National Category
Physical Sciences Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:liu:diva-121982 (URN)978-91-7685-931-5 (ISBN)
Public defence
2015-11-12, Resuren (Pronova), Campus Norrköping, Norrköping, 10:00 (English)
Opponent
Supervisors
Available from: 2015-10-14 Created: 2015-10-14 Last updated: 2017-02-03Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text

Authority records BETA

Bubnova, OlgaUllah Khan, ZiaMalti, AbdellahBraun, SlawomirFahlman, MatsBerggren, MagnusCrispin, Xavier

Search in DiVA

By author/editor
Bubnova, OlgaUllah Khan, ZiaMalti, AbdellahBraun, SlawomirFahlman, MatsBerggren, MagnusCrispin, Xavier
By organisation
Department of Science and TechnologyThe Institute of TechnologySurface Physics and ChemistryPhysics and Electronics
Engineering and Technology

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 2777 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf