Modélisation de la ségrégation solutale et application à la purification du silicium photovoltaïque

La purification du silicium joue un rôle essentiel pour la production de cellules photovoltaïques. Dans le but de diminuer le coût et l'impact environnemental associés à cette étape, un procédé de purification alternatif est en développement à l'INES (Institut National de l'Energie Solaire). L'une des étapes de ce procédé consiste à éliminer les impuretés métalliques par ségrégation lors d'un processus de solidification dirigée. L'efficacité de ce procédé est directement liée au transport convectif des impuretés dans la phase liquide. Notre étude porte donc sur la modélisation du phénomène de ségrégation et sur l'optimisation du procédé par un système de brassage mécanique. Une étude numérique basée sur des simulations en régime transitoire a été réalisée. Dans un premier temps, des simulations de ségrégation en 2D ont permis de confirmer le domaine de validité d'un modèle analytique de ségrégation. Puis, dans un second temps, l'écoulement généré par le système de brassage a été caractérisé à l'aide de simulations numériques en 3D. Ces résultats numériques ont pu être comparés à des mesures de champ de vitesse réalisées par PIV sur un dispositif expérimental en eau

Process optimization for edge passivation and high efficiency shingle heterojunction cells compatible with industry

International audienceThe aim of this work is to provide optimization solutions for silicon heterojunction shingle solar (SHJ) cell edge passivation and make them more efficient, reliable and compatible with industry. From the ALD AlOx edge passivation solution successfully developed at CEA, the approach consist in investigating three ways of improvements: (i) the time spent between the separation process and the edge passivation treatment, (ii) the lower acceptable AlOx layer thickness and (iii) the capability of doing the AlOx edge passivation at the string level before PV module integration. This work is an update of the edge passivation solution developed at CEA

Device for characterising a liquid material

A device for characterising at least one liquid material includes an analysis head and a rotating mechanical mixer. The mixer includes a central part having an internal cavity which forms an analysis chamber, a first end connected to the analysis head, and a plurality of stirring blades which are connected to a second end that is hollow so as to ensure fluid communication between the internal cavity and the liquid bath. The mechanical stirring blades are intended to be totally submerged, the central part comprises one or more openings intended to be partially submerged, and each mechanical stirring blade comprises at least one stirring flange oriented at a non-zero angle of orientation

Device for characterising a liquid material

A device for characterising at least one liquid material includes an analysis head and a rotating mechanical mixer. The mixer includes a central part having an internal cavity which forms an analysis chamber, a first end connected to the analysis head, and a plurality of stirring blades which are connected to a second end that is hollow so as to ensure fluid communication between the internal cavity and the liquid bath. The mechanical stirring blades are intended to be totally submerged, the central part comprises one or more openings intended to be partially submerged, and each mechanical stirring blade comprises at least one stirring flange oriented at a non-zero angle of orientation

Process optimization for edge passivation and high efficiency shingle heterojunction cells compatible with industry

International audienceThe aim of this work is to provide optimization solutions for silicon heterojunction shingle solar (SHJ) cell edge passivation and make them more efficient, reliable and compatible with industry. From the ALD AlOx edge passivation solution successfully developed at CEA, the approach consist in investigating three ways of improvements: (i) the time spent between the separation process and the edge passivation treatment, (ii) the lower acceptable AlOx layer thickness and (iii) the capability of doing the AlOx edge passivation at the string level before PV module integration. This work is an update of the edge passivation solution developed at CEA

Attempt to correlate dislocations network and distribution to macroscale plane rotations in <001> cast-mono ingots

International audienceThis work aims to contribute to the understanding of the mechanisms behind electricallyactive crystalline defect formation in cast-mono (cm) ingots grown along the axis. Boththe spatial distributions of background dislocations in the cellular dislocation array and the drivingforce for dislocation multiplication in the sub-grains are not perfectly understood. Macroscalelength crystal rotations are here characterized by the ($\theta$/2θ) X-ray diffraction (XRD) method atdifferent ingot heights and along two perpendicular sample axes. XRD measurements show thepresence of crystal rotations in the large single grain domain. Two orthogonal misorientationscomponents are found to evolve linearly along each sample axis forming plane orientationgradients up to (0.05±0.02) degree/cm extending over 12 cm inside the cast-mono grain. (001)crystal structure deformation are also analysed by rocking curve imaging (RCI) using synchrotronradiation on wafers of a neighboring brick. First, results confirm the presence of the planeorientation gradient measured by XRD and its order of magnitude. Second, RCI resultsdemonstrate that the plane orientation gradient is associated to the cellular dislocation network.Therefore, these results strongly suggest that background dislocations network of a cellular formcan create an organized orientation gradient at large distance within the ingot. The involvementof the characterized orientation gradients in the formation and extension of electrically activeSGBs in cast-mono ingots is discussed

Mechanical stirring: novel engineering approach for in situ spectroscopic analysis of melt at high temperature

International audienceThis paper proposes a novel engineering approach to control molten metals at high temperatures considering the industrial environment of such materials. To reduce analysis time and cost, in-line analysis techniques are more advantageous as they provide real-time information about melt composition. For this reason, recent research works focus on the development of new devices based on LIBS (Laser Induced Breakdown Spectroscopy). These devices allowed for analyzing impurities inside molten metals with great performance. However, improvements related to the immersion probe conception are still required. Indeed, the previous design used bubbling inside the melt, leading to spatial instabilities of the surface analyzed by LIBS. The solution presented here is mechanical stirring by innovative rotary blades which will be a part of an immersion LIBS probe. Their rotation will generate a representative, renewed, and stable surface that will be targeted by spectroscopic techniques in general and particularly by LIBS laser for molten metal monitoring at high temperatures. This solution was validated using experimental tests based on particle imaging velocimetry (PIV) in water at room temperature and then applied to silicon melt at high temperatures. To do so, it was necessary to design a system that allows the introduction of the blade in the melt and controls its rotation

On the defect responsible for the carrier injection-induced degradation of uncompensated n-type Czochralski silicon

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Present‐day deformations of the Jura arc inferred by GPS surveying and earthquake focal mechanisms

International audienceThis study presents a compilation of more than 40 years of seismotectonic data, including 54 computed focal mechanisms, combined with 15 years of GPS data coming from a dense network of 35 permanent GPS stations within the Jura arc and its vicinity. These data are compared to previous available geomorphological, geophysical, and structural studies in order to discuss the 3D distribution of the deformation within the Jura arc. GPS data show coherent schemes in terms of velocities and allowed to discriminate between two provinces (NE of the belt and in its front/foreland). They also constrain a low but significant overall strain tensor with a NNW-SSE shortening of 2.16 nanostrain/year associated with an ENE-WSW extension of 0.44 nanostrain/year. The seismotectonic approach is based on a data set of 2,400 events and 54 focal mechanisms. Inversions of the focal mechanisms both globally and in homogeneous sectors highlight a general strike-slip deformation regime, with sigma1 oriented NW-SE and sigma3 oriented NE-SW. We discriminate two different sectors in terms of basement/cover (un)coupling: (1) potentially decoupled deformation between the basement and the sedimentary cover in the NE part; and (2) coupled deformation in the sedimentary cover and its basement in the Jura foreland