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The trailing vortex system near impeller blades has been identified as the major flow mechanism responsible for mixing and dispersion in stirred vessels

At platinum electrodes kinetics of the I − /I 3 − electrode reaction were studied at two potential electrolyte systems for dye-sensitized solar cells ͑DSSCs͒ based on binary ionic liquid ͑IL͒ blends, i.e., 1-ethyl-3-methylimidazolium dicyanamide ͓͑EMIM͔ ͓N͑CN͒ 2 ͔͒/1-methyl-3-propylimidazolium iodide ͓͑PMIM͔I͒ and 1-ethyl-3-methylimidazolium tetrafluoroborate ͓͑EMIM͔ ͓BF 4 ͔͒/͓PMIM͔I, 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 % ͓PMIM͔I ͑for ͓EMIM͔͓N͑CN͒ 2 ͔/͓PMIM͔I͒ and 10 mol % ͓PMIM͔I ͑for ͓EMIM͔͓BF 4 ͔/͓PMIM͔I͒ up to 100 mol % ͓PMIM͔I. 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.

In this paper, we report on the outcome of a German network project conducted with 12 partners from universities and research institutes on the material development of dye solar cells (DSC). We give an overview in the field and evaluate the concept of monolithic DSC further with respect to upscaling and producibility on glass substrates. We have developed a manufacturing process for monolithic DSC modules which is entirely based on screen printing. Similar to our previous experience gained in the sealing of standard DSC, the encapsulation of the modules is achieved in a fusing step by soldering of glass frit layers. For use in monolithic DSC, a platinum free, conductive counter electrode layer, showing a charge transfer resistance of R CT < 1Á5 V cm 2 , has been realized by firing a graphite/carbon black composite under an inert atmosphere. Glass frit sealed monolithic test cells have been prepared using this platinum-free material. A solar efficiency of 6% on a 2Á0 cm 2 active cell area has been achieved in this case. Various types of non-volatile imidazolium-based binary ionic liquid electrolytes have been synthesized and optimized with respect to diffusion-limited currents and charge transfer resistances in DSC. In addition, quasi-solid-state electrolytes have been successfully tested by applying inorganic (SiO 2 ) physical gelators. For the use in semi-transparent DSC modules, a polyol process has been developed which resulted in the preparation of screen printed, transparent catalytic platinum layers showing an extremely low charge transfer resistance (0Á25 V cm 2 ).

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