Conducting polymers can have a number of different applications in photovoltaics, i.e. as the light harvester and charge transporter in bulk heterojunction cells, or as the hole transporter in dye sensitized solar cells. In these applications, properties such as the conductivity and morphology are paramount.
Ionic liquids - liquids composed entirely of ions – are of increasing interest to the photovoltaic community as they are excellent electrolytes, with negligible vapor pressures and stabilities that can significantly increase the lifetimes of photoelectrochemical cells.
However, ionic liquids are also ideal media for both chemical and electrochemical synthesis. We have utilized ionic liquids for the chemical and electrochemical synthesis of conducting polymers poly(pyrrole), poly(terthiophene) and PEDOT.[1] Electrochemical synthesis of these polymers in ionic liquids can yield smoother surface morphologies and improved electrochemical activities, which is predicted to be greatly beneficial for the performance of these materials as hole transporters.
The use of ionic liquids for the chemical synthesis of conducting polymers can also be extremely advantageous, used either in one phase or as part of a biphasic system. Conducting polymer-noble metal nanocomposites can be synthesised using a one-phase ionic liquid system, while using a biphasic ionic liquid/water system can yield conducting polymers with unusual fibrillar morphologies (Figure 1).[2] The testing of such fibrillar conducting polymers in bulk heterojunction systems will be reported.

Figure 1; TEM of PEDOT fibrils synthesized in a biphasic ionic liquid/water system.

[1] Pringle et al. Polymer, 2005, 46, 2047-2058.
[2] Pringle et al. Macromolecules, 2007, 40, 2702-2711.