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1 Introduction
Low-cost solution processable manufacturing techniques have started to be an alternative to the traditional photolithographical manufacture of electronic devices, which requires long and expensive production steps. Microcontact printing ([7] Huck, 2007), screen printing ([12] McGarry and Tarr, 2008), ink-jet printing ([17] Tekin et al. , 2008) and line patterning ([6] Hohnholz et al. , 2005) are among the most commonly used solution-based manufacturing techniques. These methods not only reduce the number of fabrication steps but also eliminate the need for high-vacuum processing, such as chemical vapour deposition and plasma etching. The possibility of using different substrates, e.g. flexible polymers, is another important advantage of these new techniques.
Poly-3-4-ethyleneoxythiophene/poly-4-sytrensulfonate (PEDOT/PSS), which is one of the intrinsically conductive polymers, is used in this study as active material to form conductive patterns onto mechanically flexible substrates. In late 1980s, the precursor of PEDOT/PSS, which is ethylenedioxithiophene (PEDOT), was chemically polymerized at Bayer AG research laboratories ([3] Bayer AG, 1988). This polymer has a high conductivity (∼300 S/cm) and high stability in the oxidized state ([4] Dietrich et al. , 1994). However, the insolubility of PEDOT limits its application. In the early 1990s, Bayer developed a new polymer by adding the water soluble electrolyte, which is poly(styrene sulfonic acid), during the polymerization of PEDOT. This process results in a water soluble conducting polymer with high stability and good film-forming properties. The physical properties of PEDOT/PSS dispersion used in this study can be seen in Table I [Figure omitted. See Article Image.]. For simplicity, PEDOT/PSSa and PEDOT/PSSb will be used in this chapter for the aqueous dispersions of Baytron P and Baytron PHC V2, respectively.
It is possible to selectively deposit this material onto flexible substrates via different methods. In this paper, line patterning, which is a relatively new patterning technique and ink jet printing have been used to transfer controlled patterns of PEDOT/PSS onto flexible substrates including polyethylene terephthalate (PET), polyimide and paper. The effects of the number of multi layers and post treatments on electrical resistivity of the patterned layers have also been investigated here.
2 Line-patterning of poly-3-4-ethyleneoxythiophene/poly-4-sytrensulfonate
Among other printing methods, line patterning, introduced by MacDiarmid and coworkers ([5] Hohnholz and MacDiarmid, 2001), is the simplest and the cheapest method. This method...