PEDOT:PSS

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.

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 high boiling solvents like methylpyrrolidone, dimethyl sulfoxide, sorbitol are added conductivity increases many orders of magnitude which 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.

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

• Conductive polymer
• Polythiophene