In situ Photopolymerization of a Gel Ionic Liquid Electrolyte in the Presence of Iodine and Its Use in Dye Sensitized Solar Cells a Orawan Winther-Jensen,* Vanessa Armel, Maria Forsyth, Douglas R. MacFarlane Introduction Several studies have been published in the search for a stable solid state electrolyte for dye sensitized solar cells (DSSCs). The quasi-solid or gelled electrolyte [1–11] is one of the approaches used to aid in manufacturability and to avoid problems associated with electrolyte loss through leakage via seals. Various methods have been used to prepare polymer or gel electrolytes; most researchers have used either heat or solvent or a combination of both to prepare a physical gel electrolyte, [1–11] i.e., a gel based on colloidal particle interactions or polymer entanglement. An important characteristic of such gels is that they usually have a ‘‘melt’’ temperature at which they will flow. The polymer or gel electrolyte can be produced either by mixing the polymer or co-polymer with a solvent at room temperature, casting over the dyed film and allowing the solvent to evaporate [1] or by mixing a preformed polymer at room temperature with solvent [2] or ionic liquid (IL) [3] to create the gel and then filling this into the DSSC at elevated temperature. Other researchers have soaked a preformed gel in a solvent-based electrolyte and then sandwiched it between the working and counter electrodes. [4] Organoge- lators, [5] SiO 2 compounds, [6] and inorganic nanoparticles (NPs) and nanocomposites [7–11] have also been used to support gelation. Some reports have also shown improve- ment of solar cell efficiency by incorporation of TiO 2 [7,11] or clay nanocomposites (e.g., MMT) [10] into the electrolyte. The ideal gel electrolyte would be one based on non- volatile components, e.g., an IL, gelled by in situ polymer- ization of a cross-linked network. [12] Such gels are Communication O. Winther-Jensen, V. Armel, D. R. MacFarlane School of Chemistry, Monash University, Clayton, VIC 3800, Australia E-mail: orawan.winther-jensen@sci.monash.edu.au M. Forsyth Department of Material Engineering, Monash University, Clayton, VIC 3800, Australia a : Supporting information for this article is available at the bottom of the article’s abstract page, which can be accessed from the journal’s homepage at http://www.mrc-journal.de, or from the author. We report for the first time an in situ photopolymerization of model co-monomers, 2- hydroxyethyl methacrylate (HEMA) and tetra (ethylene glycol) diacrylate (TEGDA), in an IL electrolyte containing I 2 for DSSCs. TiO 2 nanoparticles were used as the photo-initiator and co- gelator in a charge transfer polymerization reac- tion. The gel-IL polymer obtained was character- ized in terms of the diffusion properties of the electrolyte. Preliminary results from DSSCs assembled using the gel-IL electrolyte showed energy conversion efficiency of 3.9% at 1 sun (AM1.5) and 5.0% at 0.39 sun illumination. Macromol. Rapid Commun. 2010, 31, 479–483 ß 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim DOI: 10.1002/marc.200900701 479