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Electrolytes for Dye-Sensitized Solar Cells Based on Interhalogen Ionic Salts and Liquids

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journal contribution
posted on 30.04.2007, 00:00 by Mikhail Gorlov, Henrik Pettersson, Anders Hagfeldt, Lars Kloo
In this paper, we report on the preparation of interhalogen ionic liquids of the general formula [K+]XY2-, where K+ = 1,3-dialkylimidazolium, 1,2,3-trialkylimidazolium, or N-alkylpyridinium; XY2- = IBr2- or I2Br-. These compounds were characterized in solution and the solid state by NMR, IR, Raman, and mass spectroscopy. The crystal structure of the compound [Me2BuIm]IBr2 (7) shows that the IBr2- anion has a linear Br−I−Br structure. Indications of an equilibrium between different forms of XY2- anions in solution are observed. Interhalogen ionic salts and liquids were used as electrolyte components for encapsulated monolithic dye-sensitized solar cells. Overall light-to-electricity conversion efficiencies up to 6.4%, 5.0%, and 2.4% at 1000 W/m2 were achieved by using electrolytes based on interhalogen ionic salts and γ-butyrolactone, glutaronitrile, or native ionic liquids as solvents, respectively. Moreover, in terms of stability, the cell performance lost 9−14% of the initial performance after 1000 h illumination at 350 W/m2.