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 Volume 80, Number 51 CENEAR 80 51 p. 6 ISSN 0009-2347 |
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SCIENCE
Ionic liquid polymer gel employed as electrolyte for photovoltaic cell A gel consisting of a room-temperature ionic liquid and a stable polymer serves as an electrolyte in a high-efficiency dye-sensitized solar cell. The cell, which has a light-to-energy conversion efficiency of 5.3%, was fabricated by chemists Shaik M. Zakeeruddin and Michael Grätzel at the Swiss Federal Institute of Technology in Lausanne and coworkers [Chem. Commun., 2002, 2972].
The new gel is mechanically stable and flexible. It also offers the benefits of ionic liquids, such as negligible vapor pressure, nonflammability, and high ionic conductivity, Zakeeruddin says. "We can form a rubberlike sheet from the gel that can be cut into pieces for use in solar cells," Zakeeruddin tells C&EN. "The electrolyte is also free of organic solvents and therefore does not destroy the plastic substrate." The cell consists of a solid thin film of the electrolyte sandwiched between a counterelectrode and a nanocrystalline TiO2 electrode coated with a light-harvesting dye. The electrolyte contains an iodide/ triiodide redox couple, which allows electrical charge to be transported between the electrodes. The polymer is poly(vinylidenefluoride-co-hexafluoropropylene). The ionic liquid, 1-methyl-3-propylimidazolium iodide, is used as a source of iodide ions. "The fact that room-temperature ionic liquids work efficiently as mediators in these cells is in itself fundamentally interesting," comments C. Michael Elliott, chemistry professor at Colorado State University, "and the fact that they also function efficiently in gelled form might potentially be of practical importance." He adds, however, that problems such as the corrosiveness of the iodide/triiodide system to metals need to be overcome before such cells become commercially viable. |
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