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Various types of next-generation encapsulation films based on polyolefins have recently been introduced and could attract market attention. These material innovations can be classified as polyolefin elastomer (POE) and thermoplastic polyolefin (TPO) encapsulants, both of which consist of a polyethylene backbone with different side groups. The main advantage of these materials is the replacement of the vinyl acetate side groups of state-of-the-art encapsulant ethylene vinyl acetate (EVA) so that acetic acid cannot be formed. The main objective of this paper is to investigate the material properties of next-generation encapsulant films and compare them to an EVA reference. Two commercially available EVA alternatives (POE and TPO) have been selected. The material properties of single films as well as the electrical performance of test modules using these different encapsulants were investigated. The different films show comparable optical, thermal and thermo-mechanical properties, with slight differences in UV transparency and melting temperatures. Only shear viscosity values are higher for TPO than for POE and EVA, which requires adaption of the photovoltaic (PV) module lamination parameters. The test modules comprising the different encapsulation films show minor differences in the electrical performance after manufacturing; upon accelerated aging, no significant power loss is observed. But compared to TPO or POE, after 3000 h of damp heat exposure, test modules with EVA show the beginning of corrosion effects at the silver grid and above the ribbons. Based on the results, it can be stated that the new polyolefin encapsulation materials show great potential to be a valid replacement for EVA.

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The effects of therapeutically relevant concentrations of the human immunodeficiency virus (HIV) proteinase inhibitors saquinavir and indinavir on the in vitro proteinase activity of Candida albicans were investigated with isolates from HIV-infected and uninfected patients with oral candidiasis. After exposure to the HIV proteinase inhibitors, proteinase activity was significantly reduced in a dose-dependent manner. These inhibitory effects, which were similar to that of pepstatin A, and the reduced virulence phenotype in experimental candidiasis after application of saquinavir indicate the usefulness of these HIV proteinase inhibitors as potential anticandidal agents.

Since 2010, the ultraviolet fluorescence (UVF) method is used to identify defects in wafer-based crystalline silicon photovoltaic (PV) modules. We summarize all known applications of fluorescence imaging methods on PV modules to identify defects and characteristics. The aim of this review is to present the basic principles for the interpretation of UVF images. The method allows for detection of cell cracks in a chronological order of occurrence, visualizing hot parts in a PV module, and identifying deviating bill of materials of PV modules. The effects of various material combinations on the UVF are reproduced in the lab and explained for the first time. Seasonal effects on the UVF are presented for the first time. In addition, some not yet understood features in the images are shown and discussed. Furthermore, the application of UVF imaging for manual, hood-based, and drone-based inspection is presented. The analysis speed of the three methods has been measured under real conditions. For the manual inspection, we found an evaluation speed of 250 modules/h, for a hood-based system 200 modules/h and the drone-based method allows an imaging speed of up to 720 modules/h.

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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.

In reliability testing of components for PV modules an always remaining question is about material (in)compatibilities and synergistic effects and thus, how results of singly tested materials correlate with materials aged within PV modules. Testing of single materials would simplify sample preparation, reduce costs and offer more testing options. Therefore the main objective of this study was to compare the aging behavior of single backsheets with that of backsheets incorporated within PV modules. Four different types of backsheets were chosen, all of them comprising of polyethylene terephthalate (PET) core layers, but differing outer protection layers. Test modules using identical components, varying only in the type of backsheet used were produced and damp heat aged (85 C/85% RH 2000 h). The results revealed no influence of the PV module lamination on the thermal characteristics of the polymeric backsheets. Even after DH aging, differences between single and module laminated backsheets were negligible. Degradation effects of PET could be detected for all aged sheets by thermal analysis and were confirmed by tensile tests and rheological measurements. Thus, it can be stated that testing of single PET based backsheets under DH aging conditions is a practicable way to investigate the applicability of a new backsheet.