Temperature Dependent Impedance Analysis of Binary Ionic Liquid Electrolytes for Dye-Sensitized Solar Cells

Publisher Website
Google Scholar
Abstract
At platinum electrodes kinetics of the I−∕I3−I−∕I3− 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][N(CN)2] )/1-methyl-3-propylimidazolium iodide ([PMIM]I) and 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM] [BF4][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 9mol%9mol% [PMIM]I (for [EMIM] [N(CN)2][N(CN)2] /[PMIM]I) and 10mol%10mol% [PMIM]I (for [EMIM] [BF4][BF4] /[PMIM]I) up to 100mol%100mol% [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°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.