PEDOT:PSS

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PEDOT-PSS

PEDOT:PSS or poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (see figure) is a polymer mixture of two ionomers. One component in this mixture is made up of sodium polystyrene sulfonate which is a sulfonated polystyrene. Part of the sulfonyl groups are deprotonated and carry a negative charge. The other component poly(3,4-ethylenedioxythiophene) or PEDOT is a conjugated polymer and carries positive charges and is based on polythiophene. Together the charged macromolecules form a macromolecular salt.[1]

It is used as a transparent, conductive polymer with high ductility in different applications. For example, AGFA coats 200 million photographic films per year with a thin, extensively-stretched layer of virtually transparent and colorless PEDOT:PSS as an antistatic agent to prevent electrostatic discharges during production and normal film use, independent of humidity conditions.

If organic compounds, including high boiling solvents like methylpyrrolidone, dimethyl sulfoxide, sorbitol, ionic liquids and surfactants, are added conductivity increases by many orders of magnitude.[2][3][4] [5]This makes it also suitable as a transparent electrode, for example in touchscreens, organic light-emitting diodes and electronic paper to replace the traditionally used indium tin oxide. Due to the high conductivity (up to 1000 S/cm are possible), it can be used as a cathode material in capacitors replacing manganese dioxide or liquid electrolytes.

The conductivity of PEDOT:PSS can also be significantly improved by a post-treatment with various compounds, such as ethylene glycol, dimethyl sulfoxide (DMSO), salts, zwitterions, cosolvents, acids, geminal diols and amphiphilic fluoro- compounds.[6][7][8][9][10][11] [12][13] Recently, conductivity of more than 3000 S was observed on PEDOT:PSS treated with sulfuric acid. [14] This conductivity is comparable to that of indium tin oxide, the popular transparent electrode material.

This compound is generally applied as a dispersion of gelled particles in water. A conductive layer on glass is obtained by spreading a layer of the dispersion on the surface usually by spin coating and driving out the water by heat. Special PEDOT:PSS inks and formulations were developed for different coating and printing processes. Water based PEDOT:PSS inks are mainly used in slot die coating, flexography, rotogravure and inkjet printing. If a high viscous paste and slow drying is required like in screen-printing processes PEDOT:PSS can also be supplied in high boiling solvents like propanediol. Dry PEDOT:PSS pellets can be produced with a freeze drying method which are redispersable in water and different solvents, for example ethanol to increase drying speed during printing. Finally, to overcome degradation to ultraviolet light and high temperature / humidity conditions PEDOT:PSS UV-stabilizers are available.

Commercially available PEDOT:PSS products are produced by Heraeus with the trade name Clevios and by AGFA with the trade name Orgacon.

See also

References

  1. ↑ L. Groenendaal, F. Jonas, D. Freitag, H. Pielartzik, J. R. Reynolds, Poly(3,4-ethylenedioxythiophene) and Its Derivatives: Past, Present, and Future, Adv. Mater. 12 (2000) 481-494.
  2. ↑ J. Y. Kim, J. H. Jung, D. E. Lee, J. Joo, Enhancement of electrical conductivity of poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) by a change of solvents, Synth. Met. 2002, 126, 311-316.
  3. ↑ Jianyong Ouyang, Qianfei Xu, Chil-Wei Chu, Yang Yang, Gang Li and Joseph Shinar, On the mechanism of conductivity enhancement in poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) film through solvent treatment, Polymer 45 (2004) 8443-8450
  4. ↑ Markus Döbbelin, Rebeca Marcilla, Maitane Salsamendi, Cristina Pozo-Gonzalo, Pedro M. Carrasco, Jose A. Pomposo, and David Mecerreyes, Influence of Ionic Liquids on the Electrical Conductivity and Morphology of PEDOT:PSS Films, Chem. Mater. 19 (2007) 2147 – 2149.
  5. ↑ Benhu Fan, Xiaoguang Mei and Jianyong Ouyang, Significant conductivity enhancement of conductive poly(3,4-ethylenedioxythiophene):Poly(styrene sulfonate) (PEDOT:PSS) films by adding anionic surfactants into polymer solution, Macromolecules 41 (2008) 5971-5973.
  6. ↑ Jianyong Ouyang, Chil-Wei Chu, Fangchun Chen, Qianfei Xu and Yang Yang, Highly conductive PEDOT:PSS film and its applications in optoelectronic devices, Advanced Functional Materials, 15 (2005) 203-208
  7. ↑ Yijie Xia and Jianyong Ouyang, Salt-Induced Conductivity Enhancement of Conducting Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) Films, Macromolecules 42 (2009) 4141-4147.
  8. ↑ Yijie Xia and Jianyong Ouyang, Anion effect on salt-induced conductivity enhancement of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) films, Organic Electronics 11 (2010) 1129-1135.
  9. ↑ Yijie Xia, Hongmei Zhang and Jianyong Ouyang, Highly conductive PEDOT:PSS films prepared through a treatment with zwitterions and their application in polymer photovoltaic cells, Journal of Materials Chemistry, 20 (2010) 9740-9747.
  10. ↑ Yijie Xia and Jianyong Ouyang, Significant conductivity enhancement of conductive poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) films through a treatment with organic carboxylic acids and inorganic acids, ACS Applied Materials & Interfaces, 2 (2010) 474–483.
  11. ↑ Yijie Xia and Jianyong Ouyang, PEDOT:PSS films with significantly enhanced conductivities induced by preferential solvation with cosolvents and their application in polymer photovoltaic cells, Journal of Materials Chemistry, 21 (2011) 4927-4936.
  12. ↑ Yijie Xia, Kuan Sun and Jianyong Ouyang, Highly Conductive Poly(3,4-ethylenedioxythiophene):Poly(styrene sulfonate) Films Treated with an Amphiphilic Fluoro Compound as the Transparent Electrode of Polymer Solar Cells, Energy & Environmental Science, 5 (2010) 5325-5332.
  13. ↑ Yijie Xia, Jianyong Ouyang, Highly conductive PEDOT:PSS films prepared through a treatment with geminal diols or amphiphilic fluoro compounds, Organic Electronics, 13 (2012) 1785-1792.
  14. ↑ Yijie Xia, Kuan Sun, Jianyong Ouyang, Solution-Processed Metallic Conducting Polymer Films as Transparent Electrode of Optoelectronic Devices, Advanced Materials, 24 (2012) 2436-2440.
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