Photoluminescence and electroluminescence imaging of perovskite solar cells

Fast camera‐based luminescence‐imaging measurements on perovskite solar cells are presented. The fundamental correlation between the luminescence intensity and the open circuit voltage predicted by the generalised Planck law is confirmed, enabling various quantitative methods for the detection of efficiency‐limiting defects to be applied to this new cell structure. Interstinegly, it is found that this fundamental correlation is valid only for light‐soaked devices. Copyright © 2015 John Wiley & Sons, Ltd.     

Correlation of the loss in photovoltaic module performance with the ageing behaviour of the backsheets used

The influence of the type of backsheet on the electrical performance of test modules was evaluated before and after increasing time of accelerated ageing (damp heat [DH] exposure). Besides the measurement of the electrical power of the modules and the performance of the cells by electroluminescence, the ageing‐induced changes within the polymeric encapsulate and backsheets were investigated by means of vibrational spectroscopy and by thermo analytical methods. In addition, the permeability of the backsheets in the original and aged state was determined. This wide set of test parameters and methods allowed for the detection of correlations between (i) physical and chemical properties as well as their ageing‐induced changes of the materials and (ii) the module performance. A clear dependence of the relative loss in power output upon exposure under DH conditions for 2000 h could be observed for a set of identical test modules varied in composition only in the type of back cover used. While the modules containing gas‐tight backsheets and glass experienced only little loss in the relative power output, some modules with permeable backsheets showed a significant relative decrease in the power output and fill factor in dependence of the backsheet type used. Cell degradation could be visualised by recording electroluminescence images before and after the accelerated ageing test. The permeation properties of the backsheet used and their ageing‐induced changes seem to have an influence on the module performance. However, the absolute values neither of the water vapour transmission rate (WVTR) nor of the oxygen transmission rate (OTR) are directly linked to the loss in power output upon accelerated ageing under DH conditions. It could be shown that the ageing‐induced changes (relative transmission rates) between WVTR and OTR can be correlated with the module performance. These ageing‐induced changes in the permeation behaviour of the backsheets can be explained by (i) physical changes (e.g. post‐crystallisation, changes in the crystal structure or the crystalline microstructure) and (ii) chemical ageing effects such as a decrease in the molecular mass of the polyester (PET) polymer chains because of hydrolytic polymer degradation leading to a change in the crystallisation behaviour of PET. Hydrolytic degradation (= chemical ageing) of the PET core layer was observed (with varying extent) for all PET‐based backsheets and can, thus, not be directly correlated with the loss in performance of the corresponding test modules. The physical ageing effects, however, were detected only for those backsheets showing (i) strong deviating changes in the relative permeation rates for oxygen and water vapour upon accelerated ageing and (ii) a clear loss in electrical performance. Copyright © 2015 John Wiley & Sons, Ltd.     

Starch-Derived Products for Detergents

Recent developments in the formulation of detergents have been driven by a strong consumer demand for natural and biodegradable products. Detergent manufacturers responded to this demand with corresponding products and advertising slogans such as “fully biodegradable”, “natural” or even “double natural” to oust their competitors. In a detergent formulation, starch- derived products can in principle be used for the following purposes: as the hydrophilic head group in surfactants, as the starting material for (poly)carboxylate co-builders and as the backbone of bleaching activators. Non-ionic classical surfactants can be replaced by alkylpolyglucosides (APGs), a class of products completely based on renewable resources such as glucose and fatty alcohols derived from natural fatty acids. Sodium tripolyphosphate (STPP), the product responsible for the eutrophication of surface waters, can be substituted by a combination of an inorganic zeolite and highly oxidised starch (dicarboxylic starch) or by citrate. Acetylated polyols derived from hydrogenated carbohydrates such as sorbitol can take over the function of the petrochemically-based tetraacetyl ethylene diamine (TAED) used as activator to allow perborate bleaching at lower washing temperatures.     

Identification of chemical markers for the sensory shelf-life of saveloy

The aroma composition, the microbial composition and the sensory profile were measured in sliced saveloy samples packed in modified atmosphere (MA). The main objective was to identify aroma compounds with potential as chemical markers to identify the sensory changes of saveloy. The 60 aroma compounds isolated from the saveloy samples by dynamic headspace extraction and measured by Gas Chromatography Mass Spectrometry (GC-MS) were used to model the sensory attributes sour&old odour and meaty odour using partial least squares regression (PLS). 2- and 3-methylbutanal, 2- and 3-methylbutanol, acetoin and diacetyl were found to have the highest impact on both sour&old odour and meaty odour of the samples. The results show that these four aroma compounds have high potential as chemical markers for the sensory shelf-life of sliced and MA-packed saveloy.     

Adaptation of the ToxRTool to Assess the Reliability of Toxicology Studies Conducted with Genetically Modified Crops and Implications for Future Safety Testing

To determine the reliability of food safety studies carried out in rodents with genetically modified (GM) crops, a Food Safety Study Reliability Tool (FSSRTool) was adapted from the European Centre for the Validation of Alternative Methods’ (ECVAM) ToxRTool. Reliability was defined as the inherent quality of the study with regard to use of standardized testing methodology, full documentation of experimental procedures and results, and the plausibility of the findings. Codex guidelines for GM crop safety evaluations indicate toxicology studies are not needed when comparability of the GM crop to its conventional counterpart has been demonstrated. This guidance notwithstanding, animal feeding studies have routinely been conducted with GM crops, but their conclusions on safety are not always consistent. To accurately evaluate potential risks from GM crops, risk assessors need clearly interpretable results from reliable studies. The development of the FSSRTool, which provides the user with a means of assessing the reliability of a toxicology study to inform risk assessment, is discussed. Its application to the body of literature on GM crop food safety studies demonstrates that reliable studies report no toxicologically relevant differences between rodents fed GM crops or their non-GM comparators.     

Determining profits for solar energy with remote sensing data

The objects of the article are to determine the profits for solar energy integrating remote sensing data: the optimal locations of photovoltaic and the base price of electricity resulting from solar energy. An illustrated experiment with five European countries data sets is taken. Results indicate that Germany is the only optimal region to set up photovoltaic so as to satisfy the electricity demand of the five considered. Results also show that solar energy is a promising energy source since the highest base price of electricity resulting from solar energy is only 0.35 $/kWh. The base electricity price for Germany is the lowest whereas the base electricity price for Italy is the highest. Moreover, the results further indicate that the photovoltaic module price plays a key role in determining the best appropriate region(s) to install photovoltaic and the base electricity price.     

New Carbohydrate Derivatives from Biotechnical and Chemical Processes

Starch, its derivatives and hydrolysis products are well established as industrial products for the food and technical industries. More advanced products, based on starch, are available today, manufactured by biotechnical and chemical processes. They comprise a variety of monomeric compounds like polyols, hydroxycarboxylic acids, glycosides and their derivatives obtained by esterification, etherification and amination. In addition, interesting oligomeric and polymeric products are accessible, based on starch and its derivatives. Selected examples of these products are described as well as their respective production methods. For some products the chemicals synthesis will be compared with the fermentation route, analysing the relative advantages and disadvantages of both. The wide application potential of these “new” products is illustrated with reference to their use in different industries, e. g. in the manufacturing and processing of resins, polymers, detergents, cosmetics, pharmaceuticals and processed foods. Special emphasis will be given to the structural peculiarities of these carbohydrate derivatives, for example chirality, which enables them to act as unique intermediates in the production of biologically active products.     

New Industrial Products from Starch

The industrial (non-food) use of starch and starch-based products as renewable raw materials is discussed together with examples, in the following application areas:

• –Starch as auxiliary raw material: binder, adhesive, thickener, protective colloid.
• –Starch as raw material for new products in chemical or biotechnical processes: polyols, acids, polysaccharides, enzymes.
• –Starch as filler with specific functionality for synthetic polymers to improve application properties in e. g. polyethylene, polypropylene, polystyrene, polyurethane-foams, styrene/butadiene copolymers, polyvinylchloride.
• –Starch as reactive component to be incorporated during production of synthetic polymers leading to synergistic effects: urea/formaldehyde resins, phenolic resins, alkyd- and melamine resins.
• –Starch-based active materials which either exhibit direct functionality themselves, (e. g. as surfactants, sequestrants and bleaching boosters) or which represent building blocks for the synthesis of chiral compounds for the pharmaceutical or the agro-industries.