Caractérisation et élaboration de couches minces d'alliages ternaires amorphes silicium-carbone-germanium par décomposition thermique de molécules organogermanosiliciées PDF Download
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Author: Sai͏̈d Sefiani
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ISBN:
Category :
Languages : fr
Pages : 246
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Book Description
DES COUCHES MINCES DE SILICIUM-CARBONE-GERMANIUM ET DE SILICIUM-GERMANIUM SONT OBTENUES PAR DECOMPOSITION THERMIQUE DE MOLECULES ORGANOGERMANOSILICIEES DANS UN REACTEUR DE DEPOT CHIMIQUE EN PHASE VAPEUR. L'ETUDE DE LA STABILITE THERMIQUE DES PRECURSEURS ORGANOMETALLIQUES EN FONCTION DE LEUR STRUCTURE CHIMIQUE, EST MENEE PAR FRAGMENTATION EN SPECTROMETRIE DE MASSE ET PAR ANALYSE DES GAZ DE PYROLYSE. LES CARACTERISATIONS CHIMIQUES ET STRUCTURALES DE LA PHASE SOLIDE MONTRENT QUE SUIVANT LA STRUCTURE CHIMIQUE DES PRECURSEURS ET LA TEMPERATURE DE DEPOT, DES ALLIAGES AMORPHES OU POLYCRISTALLINS DE SILICIUM-CARBONE-GERMANIUM ET SILICIUM-GERMANIUM SONT OBTENUS
Author: Sai͏̈d Sefiani
Publisher:
ISBN:
Category :
Languages : fr
Pages : 246
Get Book Here
Book Description
DES COUCHES MINCES DE SILICIUM-CARBONE-GERMANIUM ET DE SILICIUM-GERMANIUM SONT OBTENUES PAR DECOMPOSITION THERMIQUE DE MOLECULES ORGANOGERMANOSILICIEES DANS UN REACTEUR DE DEPOT CHIMIQUE EN PHASE VAPEUR. L'ETUDE DE LA STABILITE THERMIQUE DES PRECURSEURS ORGANOMETALLIQUES EN FONCTION DE LEUR STRUCTURE CHIMIQUE, EST MENEE PAR FRAGMENTATION EN SPECTROMETRIE DE MASSE ET PAR ANALYSE DES GAZ DE PYROLYSE. LES CARACTERISATIONS CHIMIQUES ET STRUCTURALES DE LA PHASE SOLIDE MONTRENT QUE SUIVANT LA STRUCTURE CHIMIQUE DES PRECURSEURS ET LA TEMPERATURE DE DEPOT, DES ALLIAGES AMORPHES OU POLYCRISTALLINS DE SILICIUM-CARBONE-GERMANIUM ET SILICIUM-GERMANIUM SONT OBTENUS
Author: Sofia Gaiaschi
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ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Despite continuous effort, thin-film silicon multi-junction solar cells are still limited by the light-induced degradation of amorphous materials that they employ - hydrogenated amorphous silicon layers (a-Si:H) or amorphous silicon-germanium (a-SiGe:H) layers. To survive, this technology must fully benefit from the ease with which it allows multi-band gap photovoltaic (PV) devices to be assembled. To this end, materials that are stable under light soaking and have an electronic band gap between that of hydrogenated microcrystalline silicon (μc-Si:H, 1.1 eV) and that of a-Si:H (1.7 eV) are needed. The goal of this PhD thesis was to develop a new class of materials satisfying all these requirements by alloying carbon and silicon. Indeed, hydrogenated microcrystalline silicon-carbon alloys (μc-Si1-xCx:H) are a promising candidate for expanding the toolbox of useful materials for thin-film photovoltaics. The interest in these alloys lies in the possibility of easily varying their effective band gap by changing the amount of carbon in their composition. In this thesis, the usefulness of such materials in thin-film PV devices was probed using a broad range of deposition and characterization techniques. Using thin-film growth techniques at low temperatures (175-300° C), the range in which such electronically useful materials can be grown has been explored. It was confirmed that even in the condition of small crystallites, no stable sub-stoichiometric Si-C crystalline phase exists (i.e. no parallel for silicon-rich c-SiGe has been observed). Under all deposition techniques utilized, these materials were composed of submicron-size silicon crystallites embedded in an amorphous silicon-carbon (a-Si1-xCx:H) matrix. However, while the presence of the crystallites assures a higher conductivity compared to a-Si1-xCx:H, the carbon incorporation leads to an effective energy gap larger than that of microcrystalline silicon, supporting our investigation of these materials as promising optoelectronic layers. In the first part of this work, different Plasma Enhanced Chemical Vapor Deposition strategies have been investigated to achieve the widest range of processing conditions and to learn the most about the growth conditions required to produce a high quality μc-Si1-xCx:H material. Material properties were extensively characterized both on the structural side and also from an electrical point of view, in order to establish a correlation between the deposition parameters and the microstructural, transport and defect-related properties. The extensive set of results has allowed the proposal of a coherent growth model for such μc-Si1-xCx:H thin films. Exploiting these results, PV devices using these alloys as active layers were made. Although the absolute levels of efficiency (around 3.5 %) are not as high as state-of-the-art microcrystalline silicon, this work showed that it is possible to obtain variations in the open circuit voltage by varying the amount of carbon incorporated in such μc-Si1-xCx:H alloys. This important result shows that a process parameter other than silane dilution can be used to control this aspect of device performance. PV performances are modest so far, which is expected as these are the first ever results concerning the application of such a new class of materials as the active layer in thin-film solar cells. However, with further advancements in such materials, their replacement of the less stable a-SiGe:H is not unforeseeable.
