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- McHugo, S. A., et al.
(författare)
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Nanometer–scale metal precipitates in multicrystalline silicon solar cells
- 2001
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 89:8, s. 4282-4288
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we have utilized characterization methods to identify the nature of metal impurityprecipitates in low performance regions of multicrystalline silicon solar cells. Specifically, we haveutilized synchrotron-based x-ray fluorescence and x-ray absorption spectromicroscopy to study theelemental and chemical nature of these impurity precipitates, respectively. We have detectednanometer-scale precipitates of Fe, Cr, Ni, Cu, and Au in multicrystalline silicon materials from avariety of solar cell manufacturers. Additionally, we have obtained a direct correlation between theimpurity precipitates and regions of low light-induced current, providing direct proof that metalimpurities play a significant role in the performance of multicrystalline silicon solar cells.Furthermore, we have identified the chemical state of iron precipitates in the low-performanceregions. These results indicate that the iron precipitates are in the form of oxide or silicatecompound. These compounds are highly stable and cannot be removed with standard siliconprocessing, indicating remediation efforts via impurity removal need to be improved. Futureimprovements to multicrystalline silicon solar cell performance can be best obtained by inhibitingoxygen and metal impurity introduction as well as modifying thermal treatments during crystalgrowth to avoid oxide or silicate formation.
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| 3. |
- Hermann, G, et al.
(författare)
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Platform-to-platform sample transfer, distribution, dilution, and dosing via electrothermal vaporization and electrostatic deposition
- 2004
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Ingår i: Spectrochimica Acta Part B: Atomic Spectroscopy. - : Elsevier BV. - 0584-8547. ; 59:5, s. 737-48
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Tidskriftsartikel (refereegranskat)abstract
- A novel system for solid sample pretreatment, handling and dosing for analytical atomic spectrometry is described. A primary solid or liquid sample is vaporized in a graphite furnace and then condensed in a specially designed condensation zone. On the further transport path, the analyte aerosol can be diluted and distributed in pre-set ratios in the laboratory made flow control system. Applying a corona discharge, aerosol particulates are then quantitatively re-collected by means of intra-furnace electrostatic precipitation on the platform of another graphite furnace or by external precipitation on one or a set of platforms. This makes possible to produce a set of secondary platforms with equal analyte compositions from one individual primary sample. Such multitudes allow sequential multi-element determinations with single-element instrumentation or comparative measurements with different techniques. Furthermore, the described procedure allows external thermal sample pretreatment with preceding pyrolysis and additional vaporization, condensation, and re-precipitation that significantly reduces or removes the sample matrix. Owing to different losses, transport efficiencies of electrothermal vaporization (ETV) instrumentation depend on analyte element, matrix, vaporization temperature, ramp rate, and tube history. In order to reduce the losses and therewith such dependencies of the losses, new laboratory constructed ETV unit with analyte condensation in an axially focusing upstream convection zone has been constructed. Analytical performance of the new setup is compared with the performance of a commercial end-on flow-through ETV unit when analyzing both liquid dosed samples and certified solid reference materials. The new system shows much higher transport efficiencies that are, in addition, more uniform for elements of different volatility. The effects of chemical sample modifiers and elements supporting analyte condensation are studied. Most of the analytical measurements were carried out with a continuum source coherent forward scattering multi-element spectrometer. Comparative measurements were also carried out independently in the co-authors’ laboratories with atomic absorption and inductively coupled plasma mass spectrometry techniques.
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| 4. |
- Iregren, A, et al.
(författare)
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Effects on the nervous system in different groups of workers exposed to aluminium
- 2001
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Ingår i: Occupational and Environmental Medicine. ; 58, s. 453-60
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE - To investigate possible neurotoxic effects in groups of aluminium pot room and foundry workers, aluminium welders, and a small group of workers exposed to aluminium in the production of flake powder.METHODS - Exposure to aluminium was evaluated with aluminium concentrations in blood and urine as well as a questionnaire. The groups exposed to aluminium were compared with a group of mild steel welders. Neurotoxic effects were studied with mood and symptom questionnaires and several psychological and neurophysiological tests.RESULTS - The pot room and foundry workers showed very low aluminium uptake as their aluminium concentrations in blood and urine were close to normal, and no effects on the nervous system were detected. The group of workers exposed to flake powder had high concentrations of aluminium in blood and urine, even higher than those of the aluminium welders. However, aluminium could not be shown to affect the functioning of the nervous system in flake powder producers. Although significant effects could not be shown in the present analysis of the data on welders, the performance of the welders exposed to high concentrations of aluminium was affected according to the analyses in the original paper from this group.CONCLUSIONS - For the pot room and foundry workers no effects related to the exposure to aluminium could be found. For the group of flake powder producers exposed for a short term no effects on the nervous systems were evident despite high levels of exposure. Due to the high concentrations of aluminium in the biological samples of this group, measures to reduce the exposure to aluminium are recommended, as effects on the central nervous system might develop after protracted exposures. However, this assumption needs to be verified in further studies.
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