Cette thèse porte sur l’étude des effets de la lumière sur une jonction tunnel magnétique (JTM). Une JTM est constituée d’une couche isolante d’épaisseur nanométrique située entre deux couches magnétiques. Lorsqu’un courant électrique est injecté dans une telle structure, une tension apparaît. Cette tension dépend de l’orientation relative des aimantations des 2 couches magnétiques : c’est l’effet de magnétorésistance tunnel. Nous avons pu montrer dans ce travail de thèse qu’une observation similaire est obtenue lorsque la jonction est irradiée avec de la lumière. En étudiant l’influence du substrat, de la position du faisceau lumineux, de la longueur d’onde de la lumière ainsi que de la réponse du système a un pulse laser, nous avons pu mettre en évidence la présence d’effets photovoltaïque et Seebeck. Ces résultats montrent qu’il est possible, grâce à la lumière solaire, de lire l’information de mémoires magnétiques (type M-RAM) constituées d’une JTM / This thesis is devoted to the study of the effects of light on a magnetic tunnel junction (MTJ). A MTJ is made of a nanometer thick insulating layer sandwiched between the two magnetic layers. When an electric current is injected into such a structure, a voltage can be measured across the insulating layer. This voltage depends on the relative orientation of the magnetizations of the two magnetic layers. This is known as the tunnel magneto-resistance effect. We have shown in this thesis that voltage depending on the orientation of the magnetic layers can be measured when the junction is illuminated with light. By studying the influence of the substrate, the position of the light beam, the wave length of light and the response of the system to a laser pulse, we have been able to demonstrate the presence of photovoltaic and Seebeck effects. These results show that it is possible, thanks to the sunlight, to read the information from magnetic memory (MRAM) made of a MTJ

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This work studies various electrical properties of polymer layers of polyaniline, polythiophenes and poly(((benzothiadiazol)4,7-di(thien-2-yl)-5,6-difluoro-2,1,3-benzothiadiazol). Goal of this work is to determine electrical and photoelectrical properties as are electric conductivity, mobility of the free charge carriers, work function of the electrons and diffusion length of excitons. Conductivity was obtained through current and voltage contacts, mobility was measured by CELIV method (charge extraction by linearly increasing voltage). To determine work function a Kelvin probe was built and utilized. Diffusion length of excitons was determined from photovoltage spectrum formed by illuminating space charge region of the polymer.Space charge region on surface of the polymer can arise spontaneously or by laying suitable contact electrode. Powered by TCPDF (www.tcpdf.org)

Orientador: Ernesto Ruppert Filho / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-17T05:47:06Z (GMT). No. of bitstreams: 1 Villalva_MarceloGradella_D.pdf: 10773240 bytes, checksum: aeccba84d675a257bed00100b3d011cb (MD5) Previous issue date: 2010 / Resumo: Este trabalho é uma contribuição ao estudo de conversores eletrônicos para sistemas fotovoltaicos de geração distribuída de energia elétrica. O objetivo principal é apresentar o desenvolvimento e os resultados de um conversor eletrônico trifásico para a conexão de um conjunto de painéis solares fotovoltaicos à rede elétrica de baixa tensão. São apresentados resultados experimentais e estudos teóricos sobre a modelagem e a simulação de dispositivos fotovoltaicos, a regulação da tensão fotovoltaica, o rastreamento da máxima potência e a modelagem e o controle de um conversor eletrônico de dois estágios / Abstract: This work is a contribution to the study of power converters for photovoltaic distributed generation systems. The main objective is to present the development and results of a threephase power converter for a grid-connected photovoltaic plant. The work presents experimental results and theoretical studies on the modeling and simulation of photovoltaic devices, regulation of the photovoltaic voltage, maximum power point tracking, and the modeling and control of a two-stage grid-connected power converter / Doutorado / Energia Eletrica / Doutor em Engenharia Elétrica

Ce travail porte sur l'étude d'hétérostructures de semiconducteurs II-VI à alignements de bande de type II, en particulier sous forme de superréseaux. Il s'agit d'un système qui peut être prometteur pour une application photovoltaïque, et c'est dans cette optique qu'est orienté ce travail. Une première partie traite ainsi d'une réflexion conceptuelle sur l'apport des interfaces de type II au photovoltaïque.Nous présentons ensuite une étude sur la croissance de CdSe et ZnTe par épitaxie par jets moléculaires, sur différents substrats. Ces matériaux sont particulièrement intéressants et adaptés pour cette application car ils ont un gap direct, quasiment le même paramètre de maille, un alignement de bandes de type II, et le CdSe une bande interdite compatible avec le spectre solaire. Mais en contrepartie il s'agit de semiconducteurs binaires qui n'ont aucun atome en commun, de sorte que la croissance d'échantillons avec des épaisseurs précises à la monocouche près constitue un vrai défi. Pour cette raison nous avons procédé à une étude fine des interfaces grâce à des analyses de diffraction de rayons X et de microscopie en transmission, qui nous permet de conclure sur la nature chimique des atomes à proximité des interfaces.Vient ensuite une étude poussée de spectroscopie sur les effets des interfaces de type II sur les porteurs de charges, à travers leur énergie et cinétique de recombinaison. Nous avons développé un modèle analytique qui permet d'ajuster précisément toutes les caractéristiques observées en relation avec ces interfaces, et qui témoigne d'un mécanisme de séparation des charges très efficace. Nous montrons par la suite que ces effets observés sont des caractéristiques intrinsèques de toutes les interfaces de type II, indépendamment des matériaux et des structures, et que ceux-ci nous permettent d'extraire avec précision les valeurs des décalages de bandes entre différents matériaux à alignement de type II. / This work focuses on the study of II-VI semiconductor heterostructures with type II band alignments, especially in the form of superlattices. This is a system that can be promising for photovoltaic applications, and my work is presented in this perspective. Thus the first part deals with a conceptual reflection on the contribution of type II interfaces for photovoltaics.In a second step I present a study on the growth of CdSe and ZnTe by molecular beam epitaxy on various substrates. These materials are particularly interesting and suitable for this application because they have a direct bandgap, are almost lattice-matched, present a type II band alignment, and CdSe shows a bandgap compatible with the solar spectrum. But in return these are binary semiconductors which have no atoms in common, so that the growth of samples with specific thicknesses close to the monolayer is challenging. For this reason we conducted a detailed study at the interfaces through analysis of X-ray diffraction and transmission electron microscopy, which allows us to conclude on the chemical nature of the atoms near the interfaces.This is followed by a detailed spectroscopy study on the effects of type II interfaces on the charge carriers through their energy and kinetics of recombination. We have developed an analytical model that allows to precisely adjust all the features observed in relation to these interfaces, and shows a very efficient charge separation mechanism. We show later that these effects are inherent characteristics of all interfaces of type II, regardless of materials and structures, and that they allow us to accurately extract the values of band offsets between different materials with type II band alignments.

The master thesis focuses primarily on issues of photovoltaic cells in terms of their defects. The introductory part deals with the history of photovoltaics, their introduction into practice and finally an explanation of the photoelectric effect itself. The thesis also describes photovoltaic cells themselves. It explains their principle, advantages, disadvantages and the creation of photovoltaic systems. A substantial part of the work is focused on the topic of detection of defects using luminescent methods. Subsequently, it describes procedural defects arising from the improper handling of already manufactured products. The final part deals with the main topic of the work, which is a detection using luminescence methods and it also mentions the non-luminescence method LBIC. The practical part of the master thesis contains the analysis of the current solution and of the subsequent proposal of solution using a low cost camera. It describes how to modify the camera, verify its spectral sensitivity using a spectrometer and measure the sensitivity of the CMOS sensor. The conclusion is focused on verifying the functionality of the proposed solution on different sources of infrared radiation and photovoltaic panels themselves.

The Master’s Thesis prospects the suitability of installing a photovoltaic system and a cogeneration unit in the LIPOELASTIC manufacturing facility and proposes their actual realization. Theoretical part describes said facility, its current energy supply situation and presents the proposed realizations' principle of operation. Practical part contains concrete calculations needed for realizations' proposal and their economic evaluation both independently and jointly.

The aim of this diploma thesis is an innovation of photoluminescence measure research workplace for measurement of cells structure defects by method of transmissive illumination while employing the current methods of measurement of defect in the solar cells structure. The first part deals with explanation of historical development of solar energy, of how we can reach production of electric power with contribution of solar radiation and defines usability of solar cells in practice. The thesis further analyses a practical application of measurement via laboratory diagnostic methods used by Department of Electrotechnology Brno University of Technology. The second part is focused on mechanical design of experimental photoluminescence measure workspace used for quick diagnostic defects employing the rear arousing source for detection of defects with assistance of transmissive system of illumination. Finally, with co-operation of SOLARTEC s.r.o. three types of solar cells are measured by this new method and compared with results of measurement via diagnostic methods of LBIV (Light Beam Induced Current), LBIC (Light Beam Induced Voltage), Electroluminescence, Photoluminescence, and detection defects by radiation of Microplasma.

The Master´s thesis deals with issues of operational performance of two photovoltaic power plants. In the thesis is stated the history of photovoltaics, description of photovoltaic effect, used materials and production technology of the most used material in PV industry – Silicon. The basic parts and parameters of photovoltaic power plant are described. Thesis also solves, how could be done the first and periodically control due to relevant directives. The ways of diagnostics potentional failures, methods of measuring and the exam of monitoring system are stated. Practice part is focused on measuring and comparing operational performance of FVE Kurdějov and FVE Šakvice II. Operational performance was calculated from exported data for years 2014 and 2015. The thesis also contains measuring of each string connected to inventors, which are installed on the power plant. The result is an identification of strings with decreased operational performance. Based on that was created recommendations for optimalization and increase of the performance. The last part is software for simulation of photovoltaic power plant. This SW calculates potentional energy, which could be produced in a day with available data export. The calculation is defined by parameters, which are assigned.

This diploma thesis deals with selection, design and creation of new education materials for high school teacher supporting webpage www.studiumchemie.cz. The selection of the proper theme was done on the basis of research and evaluation of recent materials on the mentioned webpage and materials created at the Department of chemical education of Faculty of Science of Charles University in Prague. Preliminarily, the themes of synthetic macromolecular materials and new materials were selected. The convenience of the selected themes was confirmed by research and evaluation concerned to the preliminarily selected theme of recent high school textbooks and webpages. Consequently, educational materials in the form of PowerPoint presentations, websites, worksheets, tests, games and experiments focused on the themes of synthetic macromolecular substances and new materials were created. Materials were processed in accordance with the Framework Education Programme for Secondary General Education (Grammar Schools) as well as in accordance with the requirements of the Catalogue of graduation exam requirements from chemistry. The PowerPoint presentation and the webpage on synthetic macromolecular materials were roughly evaluated by group of teachers and the results of the evaluation are also part of the thesis....