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Temperature dependent impedance analysis of binary ionic liquid electrolytes for dye-sensitized solar cells

: Zistler, M.; Wachter, P.; Schreiner, C.; Fleischmann, M.; Gerhard, D.; Wasserscheid, P.; Hinsch, A.; Gores, H.J.


Journal of the Electrochemical Society 154 (2007), Nr.9, S.B925-B930
ISSN: 0013-4651
Fraunhofer ISE ()

At platinum electrodes kinetics of the I-/I-3(-) electrode reaction were studied at two potential electrolyte systems for dye-sensitized solar cells (DSSCs) based on binary ionic liquid (IL) blends, i.e., 1-ethyl-3-methylimidazolium dicyanamide ([EMIM] [N(CN)(2)])/1-methyl-3-propylimidazolium iodide ([PMIM]I) and 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM] [BF4])/[PMIM]I, respectively. The charge transfer resistances of the electrode reaction were determined via impedance spectroscopy for electrolyte blends at a mixing ratio of ILs of 9 mol % [PMIM]I (for [EMIM][N(CN)(2)]/[PMIM]I) and 10 mol % [PMIM]I (for[EMIM][BF4]/[PMIM]I) up to 100 mol % [PMIM]I. In addition, the influence of iodine concentration on the electrode reaction was investigated for both electrolyte systems. The measurements were taken in a temperature range of 25 to 60 degrees C to analyze the electrolyte properties in view of thermal stress of the DSSC for later practical application. Furthermore, exchange current densities were determined: the expected Arrhenius behavior was observed. Activation energies were obtained by fitting linearized Arrhenius plots.