2,013 research outputs found
Interdigitated back contact silicon heterojunction solar cells Towards an industrially applicable structuring method
We report on the investigation and comparison of two different processing approaches for interdigitated back contacted silicon heterojunction solar cells our photolithography based reference procedure and our newly developed shadow mask process. To this end, we analyse fill factor losses in different stages of the fabrication process. We find that although comparably high minority carrier lifetimes of about 4 ms can be observed for both concepts, the shadow masked solar cells suffer yet from poorly passivated emitter regions and significantly higher series resistance. Approaches for addressing the observed issues are outlined and first solar cell results with efficiencies of about 17 and 23 for shadow masked and photolithographically structured solar cells, respectively, are presente
Kinetics of coherent order-disorder transition in
Within a phase field approach which takes the strain-induced elasticity into
account, the kinetics of the coherent order-disorder transition is investigated
for the specific case of alloy. It is shown that a microstructure
with cubic precipitates appears as a transient state during the
decomposition of a homogeneous disordered solid solution into a microstructure
with tetragonal precipitates embedded into a disordered matrix. At
low enough temperature, favored by a weak internal stress, only
precipitates grow in the transient microstructure preceding nucleation of the
precipitates that occurs exclusively at the interface of the solid
solution with the precipitates. Analysis of microstructures at
nanoscopic scale shows a characteristic rod shape for the
precipitates due to the combination of their tetragonal symmetry and their
large internal stress.Comment: 2 postscript figures and 1 JPG pag
Design and User Satisfaction of Interactive Maps for Visually Impaired People
Multimodal interactive maps are a solution for presenting spatial information
to visually impaired people. In this paper, we present an interactive
multimodal map prototype that is based on a tactile paper map, a multi-touch
screen and audio output. We first describe the different steps for designing an
interactive map: drawing and printing the tactile paper map, choice of
multi-touch technology, interaction technologies and the software architecture.
Then we describe the method used to assess user satisfaction. We provide data
showing that an interactive map - although based on a unique, elementary,
double tap interaction - has been met with a high level of user satisfaction.
Interestingly, satisfaction is independent of a user's age, previous visual
experience or Braille experience. This prototype will be used as a platform to
design advanced interactions for spatial learning
Amplitude measurements of Faraday waves
A light reflection technique is used to measure quantitatively the surface
elevation of Faraday waves. The performed measurements cover a wide parameter
range of driving frequencies and sample viscosities. In the capillary wave
regime the bifurcation diagrams exhibit a frequency independent scaling
proportional to the wavelength. We also provide numerical simulations of the
full Navier-Stokes equations, which are in quantitative agreement up to
supercritical drive amplitudes of 20%. The validity of an existing perturbation
analysis is found to be limited to 2.5% overcriticaly.Comment: 7 figure
Current limiting and negative differential resistance in indium oxide based ceramics
Indium oxide based ceramics with bismuth oxide addition were sintered in air in the temperature range 800-1300 ÂșC. Current-voltage characteristics of In2O3-Bi2O3 ceramics sintered at different temperatures are weakly nonlinear. After an additional heat treatment in air at about 200 ÂșC samples sintered at a temperature within the narrow range of about 1050-1100 ÂșC exhibit a current-limiting effect accompanied by low-frequency current oscillations. It is shown that the observed electrical properties are controlled by the grain-boundary barriers and the heat treatment in air at 200 ÂșC leads to the decrease in the barrier height. Electrical measurements, scanning electron microscopy and X-ray photoelectron spectroscopy results suggest that the current-limiting effect observed in In2O3-Bi2O3 may be explained in terms of a modified barrier model; the observed current-limiting effect is the result of an increase of barrier height with increasing electric field, due to additional oxygen absorption. It is found that In2O3-Bi2O3-Co3O4-Cr2O3 ceramic exhibits current-voltage characteristics with negative differential resistance due to Joule micro heating.This study was performed in part in the frames of the project SEP-2003-C02-42821, CONACYT, MĂ©xico. Funding from the Royal Society, United Kingdom (2007R1/R26999) is gratefully acknowledged
Acid-induced aggregation and gelation of heat-treated chia proteins
This work studied for the first time the acid-induced aggregation and gelation of heat-treated chia protein isolates obtained by extraction at pH 10 or 12 (CPI10 and CPI12, respectively). The aggregation state of proteins was modified during acidification. The size of the aggregates was reduced for both samples when the pH decreased but below pH 4.5 further protein aggregation took place for CPI12. Gelation of CPI12 was completed after about 30 min of acidification with glucone-ÎŽ-lactone. By contrast, this period was not enough to reach a constant value in GâČ for CPI10. When gelation was ensured, confocal laser scanning micrographs from those gels revealed a coarse and irregular structure with large pores (median size of diameters: 30 Όm). Instead, micrographs from CPI12 cold gels showed a more regular and interconnected network, with smaller pores (median size of diameters: 9 Όm). These differences are consistent with a higher elastic behaviour ((Formula presented.) = 13.6 ± 0.1 Pa).Fil: LĂłpez, DĂ©bora Natalia. Universidad Nacional de Rosario. Facultad de Ciencias BioquĂmicas y FarmacĂ©uticas. Departamento de QuĂmica y FĂsica. Ărea FisicoquĂmica; Argentina. Pontificia Universidad CatĂłlica Argentina "Santa MarĂa de los Buenos Aires". Facultad de QuĂmica e IngenierĂa-Rosario; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Rosario; ArgentinaFil: Ingrassia, Romina. Universidad Nacional de Rosario. Facultad de Ciencias BioquĂmicas y FarmacĂ©uticas. Departamento de QuĂmica y FĂsica. Ărea FisicoquĂmica; Argentina. Universidad Nacional de Rosario. Facultad de Ciencias Veterinarias; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Rosario; ArgentinaFil: Busti, Pablo Andres. Universidad Nacional de Rosario. Facultad de Ciencias BioquĂmicas y FarmacĂ©uticas. Departamento de QuĂmica y FĂsica. Ărea FisicoquĂmica; ArgentinaFil: Wagner, Jorge Ricardo. Universidad Nacional de Quilmes. Departamento de Ciencia y TecnologĂa; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; ArgentinaFil: Boeris, Valeria. Universidad Nacional de Rosario. Facultad de Ciencias BioquĂmicas y FarmacĂ©uticas. Departamento de QuĂmica y FĂsica. Ărea FisicoquĂmica; Argentina. Pontificia Universidad CatĂłlica Argentina "Santa MarĂa de los Buenos Aires". Facultad de QuĂmica e IngenierĂa-Rosario; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Rosario; ArgentinaFil: Spelzini, DarĂo. Universidad Nacional de Rosario. Facultad de Ciencias BioquĂmicas y FarmacĂ©uticas. Departamento de QuĂmica y FĂsica. Ărea FisicoquĂmica; Argentina. Pontificia Universidad CatĂłlica Argentina "Santa MarĂa de los Buenos Aires". Facultad de QuĂmica e IngenierĂa-Rosario; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Rosario; Argentin
Geospatial analysis and living urban geometry
This essay outlines how to incorporate morphological rules within the exigencies of our technological age. We propose using the current evolution of GIS (Geographical Information Systems) technologies beyond their original representational domain, towards predictive and dynamic spatial models that help in constructing the new discipline of "urban seeding". We condemn the high-rise tower block as an unsuitable typology for a living city, and propose to re-establish human-scale urban fabric that resembles the traditional city. Pedestrian presence, density, and movement all reveal that open space between modernist buildings is not urban at all, but neither is the open space found in today's sprawling suburbs. True urban space contains and encourages pedestrian interactions, and has to be designed and built according to specific rules. The opposition between traditional self-organized versus modernist planned cities challenges the very core of the urban planning discipline. Planning has to be re-framed from being a tool creating a fixed future to become a visionary adaptive tool of dynamic states in evolution
Optoelectrical analysis of TCO Silicon oxide double layers at the front and rear side of silicon heterojunction solar cells
Silicon Heterojunction has become a promising technology to substitute passivated emitter and rear contact PERC solar cells in pursuance of lower levelized cost of electricity through high efficiency devices. While high open circuit voltages and fill factors are reached, current loss related to the front and rear contacts, such as the transparent conductive oxide TCO layers is still a limiting factor to come closer to the efficiency limit of silicon based solar cells. Furthermore, reducing indium consumption for the TCO has become mandatory to push silicon heterojunction technology towards a terawatt scale production due to material scarcity and costs. To address these issues dielectric layers, such as silicon dioxide or nitride cappings are implemented to reduce TCO thicknesses both diminishing parasitic absorption and material consumption. However, reducing the TCO thickness comes in cost of resistive losses. Furthermore, the TCO properties do vary with thickness and neighboring layer configuration altering the optimization frame of the device. In this paper we present a detailed analysis to quantify the optoelectrical losses trade off associated to the TCO thickness reduction in such layer stacks. Through the analysis we show and explain why experimental bifacial cells with 20 nm front and rear TCO perform at a similar level to reference cells with 75 nm under front and rear illumination reaching efficiency close to 24 at 92 bifaciality. We present as well a simple interconnection method via screen printing metallization to implement a thin TCO silicon dioxide silver reflector enhancing current density from 39.6 to 40.4 mA cm2 without compromising resistive losses resulting in a 0.2 absolute solar cell efficiency increase from a bifacial design 23.5 23.7 . Finally, following this approach we present a certified champion cell with an efficiency of 24.
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