In this study the effect of the purification of electrolyte material on the performance and long-term stability of dye-sensitized solar cells is investigated. The combined effect of purifying all the electrolyte materials has been examined, as has the effect of purifying each compound to identify those compounds worth purifying and to eliminate unnecessary production steps on an industrial scale. Statistical methods were employed to draw statistically significant conclusions from the experimental results. No effect on the initial cell performance is found in this study. The purity of the electrolyte solvent (here methoxypropionitrile) is shown to have a remarkable effect on the cell lifetime: it could even double when the cell is properly purified. It is shown that exposing the cell to even relatively small amounts of UV light resulted in cell degradation through electrolyte bleaching during a 1000 hour aging test. Here the impurities in the electrolyte solvent lead to an almost doubled rate of electrolyte bleaching under UV light. Dye-sensitized solar cells (DSSC) have the potential to become a low-cost alternative to silicon solar cells in the future. They can be made out of sustainable materials, they have a wide application area, and they are on the threshold of large-scale production.1 They are also efficient: an 11.9% efficiency record for DSSCs has been achieved.2 At the moment one of the main challenges is the cell stability. DSSC stability for approximately 20 years in outdoor conditions is an essential prerequisite for the introduction of DSSCs into the wide commercial market, e.g., in the form of building-integrated panels. The structure of DSSCs is quite complicated and unfortunately the components tend to age when the DSSC is exposed long-term to light, humidity, and extreme temperatures. 3,1,4,5,6,7,8 Material purification has been proposed to increase the stability of the cells.9-12 The use of highly pure materials is also regarded as an essential step in the preparation of most efficient cells. 13,10,14 The reported data do not, however, include direct comparisons of purified and unpurified materials, which would be essential for assessing the importance of material purification in cell fabrication. From the industrial point of view, material purification increases the production costs of the cells. Thus the necessity of material purification should be studied carefully, 1,15 just like any step that increases the complexity of the production. The objective of this study is to investigate if cell efficiency and stability increase as a result of the purification of the electrolyte material. The effect of the purification of all the electrolyte materials has been studied and the effect of each compound has been statistically compared and analyzed. The research continues in, 16 where the effect of dye purification on cell efficiency and lifetime is studied.It is still quite common in the field to utilize only a few tests, mainly IV curve measurements in aging studies, or to test the cells only at the...

Numerous oxidative transformations of lignan structures have been reported in the literature. In this paper we present an overview on the current findings in the field. The focus is put on transformations targeting a specific structure, a specific reaction, or an interconversion of the lignan skeleton. Oxidative transformations related to biosynthesis, antioxidant measurements, and total syntheses are mostly excluded. Non-metal mediated as well as metal mediated oxidations are reported, and mechanisms based on hydrogen abstractions, epoxidations, hydroxylations, and radical reactions are discussed for the transformation and interconversion of lignan structures. Enzymatic oxidations, photooxidation, and electrochemical oxidations are also briefly reported.

From identification of electrolyte degradation rates to lifetime estimations in dye solar cells with iodine and cobalt redox couples Degradation of dye solar cells is a major obstacle in their commercialization. Here we look into how much information on the degradation routes and rates one can extract from accessible measurements. Specifically we focus on tracking the color of the cell since all the main components of a dye solar cell have a specific color, and their color changes with degradation. Furthermore we look into extracting the degradation coefficients based on the specific color changes. One of the most vulnerable components of a dye solar cell is the electrolyte. Here we investigate the effect of two most interesting electrolyte compositions: 1) conventional iodine based electrolyte, which to date dominates the stability records of dye solar cells, and 2) cobalt complex electrolyte, which enables record high efficiencies. UV light is known to be highly detrimental as it destroys charge carriers-typically, a UV filter is recommended, but is it enough to prevent the loss of charge carriers? Here expectedly applying a UV filter improved the performance as the cells without a filter had only 4 ± 1 % of the initial efficiency left after a 1,000 hour light soaking test, whereas those with a filter maintained 90 ± 20 % of their initial efficiency. Applying a UV filter only hindered the loss of the charge carriers, but did not eliminate their degradation. From the color changes of the electrolyte, we could identify the degradation coefficient for these electrolytes. This analysis resulted in a highly relevant discovery: the loss rate of the charge carriers in iodine electrolyte was approximately double compared to cobalt electrolyte. Furthermore we could provide indicative estimates of future lifetimes of cells, which could be highly important in improving the lifetime of dye solar cells.

LC/MS in combination with NMR spectroscopy was shown to provide useful information on dye structure, purity, and on the efficiency of the purification methods. These methods allow for further studies of solar cell dyes, which may provide the detailed information needed for the improvement and eventual commercialization of the solar cell technology.

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