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排序方式: 共有53条查询结果,搜索用时 15 毫秒
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Wolfram Witte Daniel Abou‐Ras Karsten Albe Gottfried H. Bauer Frank Bertram Christian Boit Rudolf Brüggemann Jürgen Christen Jens Dietrich Axel Eicke Dimitrios Hariskos Matthias Maiberg Roland Mainz Max Meessen Mathias Müller Oliver Neumann Thomas Orgis Stefan Paetel Johan Pohl Humberto Rodriguez‐Alvarez Roland Scheer Hans‐Werner Schock Thomas Unold Alfons Weber Michael Powalla 《Progress in Photovoltaics: Research and Applications》2015,23(6):717-733
The gallium gradient in Cu(In,Ga)Se2 (CIGS) layers, which forms during the two industrially relevant deposition routes, the sequential and co‐evaporation processes, plays a key role in the device performance of CIGS thin‐film modules. In this contribution, we present a comprehensive study on the formation, nature, and consequences of gallium gradients in CIGS solar cells. The formation of gallium gradients is analyzed in real time during a rapid selenization process by in situ X‐ray measurements. In addition, the gallium grading of a CIGS layer grown with an in‐line co‐evaporation process is analyzed by means of depth profiling with mass spectrometry. This gallium gradient of a real solar cell served as input data for device simulations. Depth‐dependent occurrence of lateral inhomogeneities on the µm scale in CIGS deposited by the co‐evaporation process was investigated by highly spatially resolved luminescence measurements on etched CIGS samples, which revealed a dependence of the optical bandgap, the quasi‐Fermi level splitting, transition levels, and the vertical gallium gradient. Transmission electron microscopy analyses of CIGS cross‐sections point to a difference in gallium content in the near surface region of neighboring grains. Migration barriers for a copper‐vacancy‐mediated indium and gallium diffusion in CuInSe2 and CuGaSe2 were calculated using density functional theory. The migration barrier for the InCu antisite in CuGaSe2 is significantly lower compared with the GaCu antisite in CuInSe2, which is in accordance with the experimentally observed Ga gradients in CIGS layers grown by co‐evaporation and selenization processes. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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Engineering metal-impurity nanodefects for low-cost solar cells 总被引:1,自引:0,他引:1
Buonassisi T Istratov AA Marcus MA Lai B Cai Z Heald SM Weber ER 《Nature materials》2005,4(9):676-679
As the demand for high-quality solar-cell feedstock exceeds supply and drives prices upwards, cheaper but dirtier alternative feedstock materials are being developed. Successful use of these alternative feedstocks requires that one rigorously control the deleterious effects of the more abundant metallic impurities. In this study, we demonstrate how metal nanodefect engineering can be used to reduce the electrical activity of metallic impurities, resulting in dramatic enhancements of performance even in heavily contaminated solar-cell material. Highly sensitive synchrotron-based measurements directly confirm that the spatial and size distributions of metal nanodefects regulate the minority-carrier diffusion length, a key parameter for determining the actual performance of solar-cell devices. By engineering the distributions of metal-impurity nanodefects in a controlled fashion, the minority-carrier diffusion length can be increased by up to a factor of four, indicating that the use of lower-quality feedstocks with proper controls may be a viable alternative to producing cost-effective solar cells. 相似文献
5.
Zusammenfassung Die Sichtbarmachung von Luftstr?mungen h?ngt von Gewicht, Schwebef?higkeit und Leuchkraft des beigemengten Stoffes ab. Als
solcher hat sich in neuerer Zeit durch Erhitzen in Flockenform überführtes Metaldehyd recht brauchbar erwiesen. Nachstehend
wird über von Str?mungen um K?rper berichtet; die hierbei gewonnenen photographischen Aufanhamen werden gezeigt.
VDI
VDI 相似文献
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Ashish K. Verma Jay Tu J. S. Smith Hiroshi Fujioka Eicke R. Weber 《Journal of Electronic Materials》1993,22(12):1417-1420
In this work, we present electrical characterizations of n+ GaAs/low temperature (LT)-Al0.3Ga0.7As/n+ GaAs resistor structures in which the LT layers are grown at nominal substrate temperatures of 250 and 300°C. The resistivity
and Vtfl parameters of these LT-Al0.3Ga0.7As layers are compared with those of LT-GaAs and Al0.3Ga0.7As grown at a normal growth temperature of 720°C. Low-temperature Al0.3Ga0.7As layers exhibit resistivities as high as 1012 ohm-cm, nearly four orders of magnitude higher than that of LT-GaAs, and Vtfl values as high as 45 V, over twice that of LT-GaAs. We also find that the LT-Al0.3Ga0.7As materials grown at 250 and 300°C appear to show opposite and contradictory trends with respect to resistivity and Vtfl. We propose that this result can be explained by residual hopping conduction in the 250°C material. Temperature dependent
conductivity measurements confirm the presence of a hopping mechanism in LT-Al0.3Ga0.7As grown at 250°C and yield activation energies of 0.77 and 0.95 eV for LT-GaAs and LT-Al0.3Ga0.7As, respectively. 相似文献
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Vezatin, a ubiquitous protein of adherens cell-cell junctions, is exclusively expressed in germ cells in mouse testis 总被引:1,自引:0,他引:1
Hyenne V Harf JC Latz M Maro B Wolfrum U Simmler MC 《Reproduction (Cambridge, England)》2007,133(3):563-574
In the male reproductive organs of mammals, the formation of spermatozoa takes place during two successive phases: differentiation (in the testis) and maturation (in the epididymis). The first phase, spermiogenesis, relies on a unique adherens junction, the apical ectoplasmic specialization linking the epithelial Sertoli cells to immature differentiating spermatids. Vezatin is a transmembrane protein associated with adherens junctions and the actin cytoskeleton in most epithelial cells. We report here the expression profile of vezatin during spermatogenesis. Vezatin is exclusively expressed in haploid germ cells. Immunocytochemical and ultrastructural analyses showed that vezatin intimately coincides, temporally and spatially, with acrosome formation. While vezatin is a transmembrane protein associated with adherens junctions in many epithelial cells, it is not seen at the ectoplasmic specializations, neither at the basal nor at the apical sites, in the seminiferous epithelium. In particular, vezatin does not colocalize with espin and myosin VIIa, two molecular markers of the ectoplasmic specialization. In differentiating spermatids, ultrastructural data indicate that vezatin localizes in the acrosome. In epididymal sperm, vezatin localizes also to the outer acrosomal membrane. Considering its developmental and molecular characteristics, vezatin may be involved in the assembly/stability of this spermatic membrane. 相似文献
10.
M.Sc. Branca Delmonte Dr.-Ing. Sebastian Latz M.Sc. Jules Youmbi Prof. Dr.-Ing. Stefan Maas 《Bauphysik》2024,46(1):1-10
For decades efforts have been made to reduce the greenhouse gases emissions of buildings by reducing their energy demand with governmental regulations in Europe, pushing towards very low thermal transmittances (U-values) with ever thicker insulation layers for new buildings. However, there is no linear relationship between the insulation thickness and the heat losses. Therefore, above a certain thickness the consumption of buildings does not decrease significantly. Hereafter a life cycle analysis, including emissions before the building becomes operational is applied to evaluate the impact of the increasing thickness of components on the overall emissions. Publicly available product data sheets are used to compare four insulation materials under three scenarios. These analyses yield interesting results showing that energy-intensive insulation materials lead to a negative impact in the overall energy balance after a certain thickness. Even though there is not always a pronounced optimum insulation thickness, it is logical that further reductions in U-value for new buildings should hence be carefully evaluated. The results show that the optimal thickness is around 20 cm for most materials, while the important major savings come from the first 10 cm. 相似文献