| 1. |
- Hudson, Lawrence N, et al.
(författare)
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The database of the PREDICTS (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems) project
- 2017
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Ingår i: Ecology and Evolution. - : John Wiley & Sons. - 2045-7758. ; 7:1, s. 145-188
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Tidskriftsartikel (refereegranskat)abstract
- The PREDICTS project-Projecting Responses of Ecological Diversity In Changing Terrestrial Systems (www.predicts.org.uk)-has collated from published studies a large, reasonably representative database of comparable samples of biodiversity from multiple sites that differ in the nature or intensity of human impacts relating to land use. We have used this evidence base to develop global and regional statistical models of how local biodiversity responds to these measures. We describe and make freely available this 2016 release of the database, containing more than 3.2 million records sampled at over 26,000 locations and representing over 47,000 species. We outline how the database can help in answering a range of questions in ecology and conservation biology. To our knowledge, this is the largest and most geographically and taxonomically representative database of spatial comparisons of biodiversity that has been collated to date; it will be useful to researchers and international efforts wishing to model and understand the global status of biodiversity.
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| 2. |
- Barrigón, Enrique, et al.
(författare)
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Degradation of Ge subcells by thermal load during the growth of multijunction solar cells
- 2018
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Ingår i: Progress in Photovoltaics: Research and Applications. - : Wiley. - 1062-7995. ; 26:2, s. 102-111
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Tidskriftsartikel (refereegranskat)abstract
- Germanium solar cells are used as bottom subcells in many multijunction solar cell designs. The question remains whether the thermal load originated by the growth of the upper layers of the multijunction solar cell structure affects the Ge subcell performance. Here, we report and analyze the performance degradation of the Ge subcell due to such thermal load in lattice-matched GaInP/Ga(In)As/Ge triple-junction solar cells. Specifically, we have detected a quantum efficiency loss in the wavelength region corresponding to the emitter layer (which accounts for up to 20% loss in equivalent JSC) and up to 55 mV loss in VOC of the Ge subcell as compared with analogous devices grown as single-junction Ge solar cells on the same type of substrates. We prove experimentally that there is no direct correlation between the loss in VOC and the doping level of the base. Our simulations show that both the JSC and VOC losses are consistent with a degradation of the minority carrier properties at the emitter, in particular at the initial nanometers of the emitter next to the emitter/window heterointerface. In addition, we also rule out the gradual emitter profile shape as the origin of the degradation observed. Our findings underscore the potential to obtain higher efficiencies in Ge-based multijunction solar cells if strategies to mitigate the impact of the thermal load are taken into consideration.
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| 3. |
- Barrutia, Laura, et al.
(författare)
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Effect of Ge autodoping during III-V MOVPE growth on Ge substrates
- 2017
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248. ; 475, s. 378-383
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Tidskriftsartikel (refereegranskat)abstract
- During the MOVPE growth of III-V layers on Ge substrates, Ge atoms can be evaporated or etched from the back of the wafer and reach the growth surface, becoming incorporated into the epilayers. This is the so-called Ge autodoping effect, which we have studied through a set of growth experiments of GaInP and Ga(In)As layers lattice matched to Ge substrates, which have been characterized by Secondary Ion Mass Spectroscopy. The role of V/III ratio and growth rate on Ge autodoping has been studied and a MOVPE reactor pre-conditioning prior to the epitaxial growth of III-V semiconductor layers that mitigates this Ge autodoping has been identified. In addition, the use of 2-in. versus 4-in. Ge substrates has been compared and the use of a Si3N4 backside coating for the Ge substrates has been evaluated.
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| 4. |
- Barrutia, Laura, et al.
(författare)
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Impact of the III-V/Ge nucleation routine on the performance of high efficiency multijunction solar cells
- 2020
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Ingår i: Solar Energy Materials and Solar Cells. - : Elsevier BV. - 0927-0248. ; 207
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Tidskriftsartikel (refereegranskat)abstract
- This paper addresses the influence of III-V nucleation routines on Ge substrates for the growth of high efficiency multijunction solar cells. Three exemplary nucleation routines with differences in thickness and temperature were evaluated. The resulting open circuit voltage of triple-junction solar cells with these designs is significantly affected (up to 50 mV for the best optimization routine), whereas minimal differences in short circuit current are observed. Electroluminescence measurements show that both the Ge bottom cell and the Ga(In)As middle cell present a VOC gain of 25 mV each. This result indicates that the first stages of the growth not only affect the Ge subcell itself but also to subsequent subcells. This study highlights the impact of the nucleation routine design in the performance of high efficiency multijunction solar cell based on Ge substrates.
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| 8. |
- Rey-Stolle, Ignacio, et al.
(författare)
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On the thermal degradation of tunnel diodes in multijunction solar cells
- 2017
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Ingår i: 13th International Conference on Concentrator Photovoltaic Systems, CPV 2017. - : Author(s). - 9780735415614 ; 1881
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Konferensbidrag (refereegranskat)abstract
- Tunnel junctions are essential components of multijunction solar cells. These highly doped p/n junctions provide the electrical interconnect between the subcells that constitute a multijunction solar cell device. The conductivity and the peak tunneling current of tunnel diodes are known to be severely affected by thermal load. This is a general phenomenon observed in tunnel junctions despite the materials used, the dopants employed or the growth technique applied. Despite this generality, the explanations for this thermal degradation tend to be quite material/dopant specific. On the contrary, in this work we apply the amphoteric native defect model to explain this issue. In this context, the degradation can be explained as a consequence of the net loss of free carrier concentration produced by the creation of native compensating defects in the highly doped layers of the tunnel junction. Experiments carried out on n++ GaAs agree well with the model.
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| 9. |
- Volz, Erik, et al.
(författare)
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Evaluating the Effects of SARS-CoV-2 Spike Mutation D614G on Transmissibility and Pathogenicity
- 2021
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Ingår i: Cell. - : Elsevier BV. - 1097-4172 .- 0092-8674. ; 184:1, s. 11-75
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Tidskriftsartikel (refereegranskat)abstract
- Global dispersal and increasing frequency of the SARS-CoV-2 spike protein variant D614G are suggestive of a selective advantage but may also be due to a random founder effect. We investigate the hypothesis for positive selection of spike D614G in the United Kingdom using more than 25,000 whole genome SARS-CoV-2 sequences. Despite the availability of a large dataset, well represented by both spike 614 variants, not all approaches showed a conclusive signal of positive selection. Population genetic analysis indicates that 614G increases in frequency relative to 614D in a manner consistent with a selective advantage. We do not find any indication that patients infected with the spike 614G variant have higher COVID-19 mortality or clinical severity, but 614G is associated with higher viral load and younger age of patients. Significant differences in growth and size of 614G phylogenetic clusters indicate a need for continued study of this variant.
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