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| 2. |
- Adamczyk, Krzysztof, et al.
(author)
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Recombination activity of grain boundaries in high-performance multicrystalline Si during solar cell processing
- 2018
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In: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 123:5, s. 1-6
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Journal article (peer-reviewed)abstract
- In this work, we applied internal quantum efficiency mapping to study the recombination activity of grain boundaries in High Performance Multicrystalline Silicon under different processing conditions. Wafers were divided into groups and underwent different thermal processing, consisting of phosphorus diffusion gettering and surface passivation with hydrogen rich layers. After these thermal treatments, wafers were processed into heterojunction with intrinsic thin layer solar cells. Light Beam Induced Current and Electron Backscatter Diffraction were applied to analyse the influence of thermal treatment during standard solar cell processing on different types of grain boundaries. The results show that after cell processing, most random-angle grain boundaries in the material are well passivated, but small-angle grain boundaries are not well passivated. Special cases of coincidence site lattice grain boundaries with high recombination activity are also found. Based on micro-X-ray fluorescence measurements, a change in the contamination level is suggested as the reason behind their increased activity.
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| 3. |
- Castellanos, Sergio, et al.
(author)
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Inferring Dislocation Recombination Strength in Multicrystalline Silicon via Etch Pit Geometry Analysis
- 2014
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In: 2014 IEEE 40TH Photovoltaic Specialists Conference (PVSC). - : IEEE. - 9781479943982 ; , s. 2957-2959
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Conference paper (peer-reviewed)abstract
- Dislocations limit solar cell performance by decreasing minority carrier diffusion length, leading to inefficient charge collection at the device contacts [1]. However, studies have shown that the recombination strength of dislocation clusters within millimeters away from each other can vary by orders of magnitude [2]. In this contribution, we present correlations between dislocation microstructure and recombination activity levels which span close to two orders of magnitude. We discuss a general trend observed: higher dislocation recombination activity appears to be correlated with a higher degree of impurity decoration, and a higher degree of disorder in the spatial distribution of etch pits. We present an approach to quantify the degree of disorder of dislocation clusters. Based on our observations, we hypothesize that the recombination activity of different dislocation clusters can be predicted by visual inspection of the etch pit distribution and geometry.
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| 4. |
- Castellanos, Sergio, et al.
(author)
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Variation of dislocation etch-pit geometry : An indicator of bulk microstructure and recombination activity in multicrystalline silicon
- 2014
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In: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 115:18, s. 1-7
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Journal article (peer-reviewed)abstract
- Dislocation clusters in multicrystalline silicon limit solar cell performance by decreasing minoritycarrier diffusion length. Studies have shown that the recombination strength of dislocation clusterscan vary by up to two orders of magnitude, even within the same wafer. In this contribution, wecombine a surface-analysis approach with bulk characterization techniques to explore theunderlying root cause of variations in recombination strength among different clusters. We observethat dislocation clusters with higher recombination strength consist of dislocations with a largervariation of line vector, correlated with a higher degree of variation in dislocation etch-pit shapes(ellipticities). Conversely, dislocation clusters exhibiting the lowest recombination strength containmostly dislocations with identical line vectors, resulting in very similar etch-pit shapes. Thedisorder of dislocation line vector in high-recombination clusters appears to be correlated withimpurity decoration, possibly the cause of the enhanced recombination activity. Based on ourobservations, we conclude that the relative recombination activity of different dislocation clustersin the device may be predicted via an optical inspection of the distribution and shape variation ofdislocation etch pits in the as-grown wafer.
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| 5. |
- Klionsky, Daniel J., et al.
(author)
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Guidelines for the use and interpretation of assays for monitoring autophagy
- 2012
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In: Autophagy. - : Informa UK Limited. - 1554-8635 .- 1554-8627. ; 8:4, s. 445-544
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Research review (peer-reviewed)abstract
- In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field.
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| 6. |
- Norlin, Börje, associate professor, 1967-, et al.
(author)
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Visualisation of sulphur on single fibre level for pulping industry
- 2023
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In: Journal of Instrumentation. - : Institute of Physics (IOP). - 1748-0221. ; 18:01, s. C01012-C01012
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Journal article (peer-reviewed)abstract
- In the pulp and paper industry, about 5 Mt/y chemithermomechanical pulp (CTMP) are produced globally from softwood chips for production of carton board grades. For tailor making CTMP for this purpose, wood chips are impregnated with aqueous sodium sulphite for sulphonation of the wood lignin. When lignin is sulphonated, the defibration of wood into pulp becomes more selective, resulting in enhanced pulp properties. On a microscopic fibre scale, however, one could strongly assume that the sulphonation of the wood structure is very uneven due to its macroscale size of wood chips. If this is the case and the sulphonation could be done significantly more evenly, the CTMP process could be more efficient and produce pulp even better suited for carton boards. Therefore, the present study aimed to develop a technique based on X-ray fluorescence microscopy imaging (µXRF) for quantifying the sulphur distribution on CTMP wood fibres. Firstly, the feasibility of µXRF imaging for sulphur homogeneity measurements in wood fibres needs investigation. Therefore, clarification of which spatial and spectral resolution that allows visualization of sulphur impregnation into single wood fibres is needed. Measurements of single fibre imaging were carried out at the Argonne National Laboratory’s Advanced Photon Source (APS) synchrotron facility. With a synchrotron beam using one micrometre scanning step, images of elemental mapping are acquired from CTMP samples diluted with non-sulphonated pulp under specified conditions. Since the measurements show significant differences between sulphonated and non-sulphonated fibres, and a significant peak concentration in the shell of the sulphonated fibres, the proposed technique is found to be feasible. The required spatial resolution of the µXRF imaging for an on-site CTMP sulphur homogeneity measurement setup is about 15 µm, and the homogeneity measured along the fibre shells is suggested to be used as the CTMP sulphonation measurement parameter.
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| 7. |
- Åstrand, Mattias, et al.
(author)
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Multi-beam ptychography with coded in-line Fresnel zone plates
- 2023
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In: X-Ray Nanoimaging : Instruments and Methods VI - Instruments and Methods VI. - : SPIE-Intl Soc Optical Eng. - 0277-786X .- 1996-756X. - 9781510666108 ; 12698
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Conference paper (peer-reviewed)abstract
- X-ray ptychography is often implemented for nanoimaging at synchrotron radiation sources and extensions are being developed to make experiments faster. This work is on multi-beam ptychography with Fresnel zone plates that have a small lateral separation, enabling the imaging of an extended field of view without increasing exposure time. Sectional zone inversion is implemented for coding respective probes and up to three Fresnel zone plates are successfully used in parallel. The speed-up achieved, compared to single beam ptychography, is linear with the number of probes. The combination of versatility of the fabrication process for the Fresnel zone plates and performance enhancement by scanning in multi-beam mode makes this an optimal solution for studying samples fast and obtaining enlarged fields of view.
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| 8. |
- Thomas, HS, et al.
(author)
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- 2019
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swepub:Mat__t
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| 9. |
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- 2019
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Journal article (peer-reviewed)
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