Le photovoltaïque est une énergie renouvelable pouvant aider à lutter contre le réchauffement climatique et l’épuisement des ressources fossiles utilisées pour la production d’énergie. La filière émergente à base de matériaux pérovskites (photovoltaïque de 3ème génération) est très prometteuse car elle utilise des matériaux abondants et faciles à mettre en œuvre (technologie bas-coût) et a montré de plus des rendements record compétitifs en peu de temps. Il reste cependant des verrous technologiques à lever afin de pouvoir développer cette technologie à grande échelle. L’un deux consiste à améliorer la couche de TiO₂ qui transporte les électrons et dont les défauts limitent les performances et la durée de vie des cellules photovoltaïques pérovskites. Ce travail propose l’utilisation de matériaux à base de nanostructures de carbone et de TiO₂ pour améliorer le transport et la collecte des électrons au sein de ces cellules photovoltaïques et ainsi améliorer leur rendement. Pour cela, la pyrolyse laser, technique singulière de production continue de nanoparticules, a été adaptée pour l’élaboration de nanocomposites TiO₂/graphène aux propriétés contrôlées. Ces matériaux ont été caractérisés puis intégrés aux cellules photovoltaïques pérovskites qui ont démontré une meilleure efficacité en présence de graphène. Par ailleurs, ce travail présente une architecture innovante à base de nanotubes de carbone alignés verticalement, en vue d’une application pour la collecte des électrons photo-générés des cellules photovoltaïques pérovskites. Les matériaux carbonés présentent donc de fortes potentialités pour l’optoélectronique, et plus particulièrement pour le photovoltaïque de 3ème génération. / Photovoltaic is a promising renewable energy to tackle global warming and the depletion of fossil resources. The emerging field of perovskite solar cells (3rd generation photovoltaic) is very attractive because it uses abundant and easy-processing materials (low-cost technology) and provides competitive efficiencies.Still, efforts remain to be performed to develop this technology, especially concerning the improvement of efficient and reliable charge transporting electrodes. Titanium dioxide layer, commonly used for electron extraction, presents defects that limit the performance and lifetime of the perovskite solar cells.This work proposes the use of materials based on TiO₂ and carbon nanostructures to improve the electron transport and collection within the solar cells, in order to enhance the power conversion efficiency. The singular technique of laser pyrolysis, which is a continuous process of nanoparticles synthesis, was adapted to produce TiO₂/graphene nanocomposites with well-controlled properties. These materials have been characterized and integrated into perovskite solar cells that demonstrate an improved efficiency in presence of graphene.Besides, this work presents an innovating architecture based on vertically aligned carbon nanotubes for the electron collection of a perovskite solar cell. We show then the strong potential of carbon materials for optoelectronic, especially 3rd generation photovoltaic.

Les cellules solaires pérovskites hybrides ont marqué le monde du photovoltaïque avec une augmentation spectaculaire des rendements durant ces quatre dernières années. Avec des rendements dépassant 20% à l’heure actuelle, ce type de cellules suscite une attention particulière dans le monde scientifique. Dans l’architecture de la cellule solaire pérovskite, le TiO2 est l’oxyde le plus utilisé comme matériau collecteur d’électrons. Cette couche d’oxyde joue un rôle important dans la cellule, cependant le procédé d’élaboration du TiO2 requiert une étape de recuit à haute température. En plus des coûts élevés de production qu’elle implique, son utilisation exclut son application aux substrats sensibles aux hautes températures tels que les substrats plastiques flexibles par exemple.Cette thèse est centrée sur le remplacement du TiO2 par le ZnO en tant que couche collectrice d’électrons et bloqueuse de trous. Ce matériau représente une alternative intéressante en raison de ces propriétés comparables et même supérieures à celles du TiO2. L’intérêt du choix du ZnO réside dans sa simplicité de mise en œuvre. Ce matériau peut en effet être synthétisé à basse température (<100°C) et sous différentes structures. Dans cette étude nous avons fait le choix de considérer les croissances de ZnO par voie électrochimique et par pulvérisation cathodique. Dans des conditions de dépôts optimisées des couches de pérovskite et de ZnO, des rendements record de 14.2% et 9.7% ont été obtenus dans des architectures plane et nanostructurée respectivement. / Perovskite solar cells have marked the photovoltaic world with a spectacular increase of efficiencies over the last four years. With efficiencies exceeding 20%, this type of solar cells attracts a particular attention in the photovoltaic field. In the standard perovskite solar cell stack, TiO2 is used as an electron-collecting layer. This oxide layer plays an important role in the cell, however, its growth process requires a high temperature annealing step. In addition to the high production costs involved, its use also exclude its application to temperatures sensitive substrates such as flexible plastic materials.This thesis focuses on the replacement of the TiO2 bilayer by a ZnO electron-collecting and hole-blocking layer. We consider ZnO as an alternative to its comparable and even superior properties. One of the interests of the choice of ZnO lies in its simplicity of implementation and the possibility to synthesize it at low temperature (<100°C) and under different structures. The ZnO is here synthesized by electrochemical way and sputtering process. Under optimized deposition conditions of perovskite and ZnO layers, record efficiencies of 14.2% and 9.7% have been obtained in planar and nanostructured architecture respectively.

Les perovskites organiques-inorganiques en halogénures de plomb sont des matériaux très prometteurs pour la prochaine génération de cellules solaires avec des avantages intrinsèques tels que leur faible coût de fabrication (grande disponibilité des matériaux de base et leur mise en œuvre à basse température) et leur bon rendement de conversion photovoltaïque. Cependant, les cellules solaires pérovskites sont encore instables et montrent des effets d'hystérésis courant-tension délétères. Dans cette thèse, des résultats de l’analyse physique de couches minces de pérovskite à base de CH3NH3PbI3-xClx et de cellules solaires ont été présentés. Les caractéristiques de transport électrique et les processus de vieillissement ont été étudiés avec différentes approches.Dans une première étape, la synthèse du matériau pérovskite a été optimisée en contrôlant les conditions de dépôt des films en une seule étape telles que la vitesse de rotation (6000 rpm) de la tournette et la température de recuit des films (80 °C). Dans un second temps, des cellules solaires perovskites à base de CH3NH3PbI3-xClx ont été fabriquées en utilisant la structure planaire inversée et caractérisées optiquement et électriquement.Grace à l’utilisation de la spectroscopie optique à décharge luminescente (GDOES), un déplacement des ions halogénures a été observé expérimentalement et de façon directe sous l’application d’une tension électrique. Une longueur de diffusion ionique de 140 nm et un rapport de 65% d'ions mobiles ont été déduits. Il est montré que l'hystérésis courant-tension dans l'obscurité est fortement affectée par la migration des ions halogénures provoquant un écrantage substantiel du champ électrique appliqué. Nous avons donc trouvé sous obscurité un décalage de la tension à courant nul jusque 0,25 V et un courant de fuite jusque 0,1 mA / cm2 en fonction des conditions de mesure. Grâce aux courbes courant-tension en fonction de la température, nous avons déterminé la température de transition de la conductivité ions/électrons à 260K et analysé les résultats expérimentaux en utilisant l'équation de Nernst- Einstein donnant une énergie d'activation de 0.253 eV pour les ions mobiles.Enfin, le processus de vieillissement de la cellule solaire a été étudié avec des mesures optiques et électriques. Nous avons déduit que le processus de vieillissement apparaît d'abord à la surface des cristaux de pérovskite ainsi qu’aux joints de grains. Les mesures GDOES nous indiquent que les caractéristiques électriques des cellules pérovskites sont perdues par une corrosion progressive de l'électrode supérieure en argent causée par la diffusion des ions iodures. / Organic-inorganic lead halide perovskites are very promising materials for the next generation of solar cells with intrinsic advantages such as a low-cost material due to the availability of source materials and low-temperature solution processing as well as a high power conversion efficiency of the sunlight. However, perovskite solar cells are still unstable and show deleterious current-voltage hysteresis effects. Inthis thesis, analyses of CH3NH3PbI3-xClx based perovskite thin films and solar cells are presented. The electrical transport characteristics and the ageing processes are investigated using different approaches.The synthesis of the halide perovskite materials is optimized in a first step by controlling the deposition conditions such as annealing temperature (80°C) and spinning rate (6000 rpm) in the one step-spin-casted process. CH3NH3PbI3-xClx based perovskite solar cells are then fabricated in the inverted planar structure and characterized optically and electrically in a second step.Direct experimental evidence of the motion of the halide ions under an applied voltage has been observed using glow discharge optical emission spectroscopy (GDOES). Ionic diffusion length of 140 nm and ratio of mobile iodide ions of 65 % have been deduced. It is shown that the current-voltage hysteresis in the dark is strongly affected by the halide migration which causes a substantial screening of the applied electric field. Thus we have found a shift of voltage at zero current (< 0.25 V) and a leakage current (< 0.1 mA/cm2) in the dark versus measurement condition. Through the current-voltage curves as a function of temperature we have identified the freezing temperature of the mobile iodides at 260K. Using the Nernst-Einstein equation we have deduced a value of 0.253 eV for the activation energy of the mobile ions.Finally, the ageing process of the solar cell has been investigated with optical and electrical measurements. We deduced that the ageing process appear at first at the perovskite grain surface and boundaries. The electrical characteristics are degraded through a deterioration of the silver top-electrode due to the diffusion of iodides toward the silver as shown by GDOES analysis.

Orientador: Eudes Borges de Araújo / Resumo: Nos últimos anos, grande atenção tem sido dada ao desenvolvimento de células solares com o iodeto de chumbo e metilamônio (MAPbI3) em virtude de suas excelentes propriedades fotovoltaicas. Apesar de altas eficiências de conversão de energia terem sido atingidas com essas células, a síntese desse material e algumas de suas características elétricas permanecem em estudo. No presente trabalho, mostrou-se que a síntese desse material na forma de filmes finos via spin-coating deve ser executada preferencialmente com soluções precursoras de dimetilsulfóxido depositadas sobre platina, com maiores tempos e temperaturas de secagem e aumento da taxa de remoção do solvente. Por sua vez, pastilhas de MAPbI3 tiveram condições ótimas de sinterização a 120°C por 2h. O material foi caracterizado em termos de suas propriedades elétricas por meio da espectroscopia de impedância, com tensões de frequências na faixa de 300 Hz a 1 MHz e temperaturas no intervalo entre 100 e 430K, tendo sido observada uma histerese entre o aquecimento e o resfriamento nos comportamentos da permissividade elétrica, impedância, módulo elétrico e condutividade elétrica, que se mostraram sensíveis à temperatura e às frequências da tensão de teste. Ainda, foram observadas alterações dessas propriedades elétricas associadas às transições de fase, cujas temperaturas em que ocorrem se mostraram independentes da frequência da tensão. A fim de separar os efeitos diferenciados dos grãos e contornos de grão nas propriedades e... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In recent years, great attention has been paid to the manufacture of solar cells with methylammonium lead iodide (MAPbI3) due to its excellent photovoltaic properties. Although high energy conversion efficiencies have been achieved with these cells, the synthesis of this material and some of its electrical characteristics remain under study. In the present research, it was shown that the synthesis of this material in the form of spin-coating thin films should be performed preferably with dimethylsulfoxide precursor solutions deposited over platinum surfaces, with higher drying times and temperatures and increasing the solvent removal rate. In turn, MAPbI3 pellets had optimum sintering conditions at 120°C for 2h. The material was characterized in terms of it’s electrical properties by impedance spectroscopy, with frequency voltages in the range of 300 Hz to 1 MHz and temperatures in the range 100 to 430K, and a hysteresis between heating and cooling was observed on permissivity, impedance, electrical modulus and conductivity behaviors, which were sensitive to temperature and applied voltage frequencies. In addition, changes in these electrical properties associated with phase transitions were observed, whose temperatures at which they occurred were independent of the voltage frequency. In order to separate the differentiated effects of grains and grain boundaries on the electrical properties of MAPbI3, an equivalent circuit was proposed that was efficient to describe the exper... (Complete abstract click electronic access below) / Mestre

Method, so called “glycin- nitrate process”, combined with high temperature solid state reaction, of preparation multi- component ceramic perovskite materials was studied. Two types of perovskite systems were prepared by this method. Firs one, based on LaNiO3 doped by calcium and aluminium and second one, based on SmFeO3 doped by calcium and nickel or cobalt. This method made possible preparation of one phase perovskite or perovskites with few percent of nickel in form of oxide. In systems containing both nickel and calcium another phases rich in calcium and nickel appeared.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19187号 / 工博第4064号 / 新制||工||1627(附属図書館) / 32179 / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 陰山 洋, 教授 阿部 竜, 教授 田中 勝久 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

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A combustion chamber incorporating a high temperature porous matrix was design and tested. The effects and merits of combining combustion on porous media and catalytic enhancement were explored, in addition to the proof of concept of integrating these technologies with simple heat engines, such as thermoelectric generators, to generate efficient and reliable power. The direct observation of the flame during the combustion becomes possible due to a specially designed stainless steel chamber incorporating a quartz window where the initiation and propagation of the combustion reaction/flame was directly visible. The simple design of the combustion chamber allowed for a series of thermocouples to be arranged on the central axis of the porous media. With the thermocouples as output and two flow controllers controlling the volumetric flow of fuel and air as input, it was possible to explore the behavior of the flame at different volumetric flow ranges and fuel to air ratios. Additionally the design allowed for thermoelectric modules to be placed in the walls of the combustion chamber. Using combustion as a heat source and passive fins for cooling, the device was able to generate enough power to power a small portable electronic device. The effects of La-Sr-Fe-Cr-Ru based perovskite catalysts, on matrix stabilized combustion in a porous ceramic media were also explored. Highly porous silicon carbide ceramics are used as a porous media for a catalytically enhanced superadiabatic combustion of a lean mixture of methane and air. Perovskite catalytic enhancement of SiC porous matrix with La0.75Sr0.25Fe0.6Cr0.35Ru0.05O3, La0.75Sr0.25Fe0.6Cr0.4O3, La0.75Sr0.25Fe0.95Ru0.05O3, La0.75Sr0.05Cr0.95Ru0.05O3, and LaFe0.95Ru0.05O3 were used to enhance combustion. The flammability limits of the combustion of methane and air were explored using both inert and catalytically enhanced surfaces of the porous ceramic media. By coating the SiC porous media with perovskite catalysts it was possible to lower the minimum stable equivalence ratio and achieve more efficient combustion.

<p>Various transition metal oxides with interesting magnetic properties (often based on the perovskite structure) were prepared using conventional solid-state methodologies and fully characterized using a variety of techniques such as powder X-ray diffraction, variable temperature neutron diffraction, SEM-EDS, TEM-EDS, SQUID magnetometry and heat capacity measurements.</p> <p>One family of compounds that was investigated intensively were the 'pillared perovskites'. In this structure type, perovskite-like layers of comer shared octahedra are separated. by about 10 A by diamagnetic edge-shared octahedral dimer 'pillars'. Despite this long distance between layers, long-range order is present in both the La5Re3Co016 and La5Re3Ni016 members. In fact, a new magnetic structure was discovered for the Ni compound consisting of ferromagnetically ordered layers, coupled antiferromagnetically.</p> <p>In addition, for the first time, substitution of the 5+ ion within the layer was successful, yielding compounds with general formula, La5Re3-xTaxB016 (B =Mn, Fe, Co, Ni; x ~ 0.5). Surprisingly, despite replacing about half of the magnetic ions within the perovskite layers with non-magnetic tantalum, the materials had the same ordering temperatures and magnetic structures as their unsubstituted analogues. This observation is evidence that the longer interlayer coupling pathway is the key to long-range ordering in this structure type.</p> <p>The lanthanum rhenium oxide, La3Re20 10, involves the edge-shared octahedral dimer 'pillar' unit from the pillared perovskite structure, but with one unpaired electron per dimer unit. Prepared for the first time by solid-state synthesis, and studied magnetically in depth, long-range order was evident at 18 K. Theoretical investigations hinted that the magnetic structure consists of antiferromagnetically coupled chains of dimers, coupled antiferromagnetically.</p> <p>The magnetic properties of the double perovskite, SrLaRuNi06, were also explored for the first time. This study demonstrates the power of neutron diffraction at elucidating magnetic information, such as the ordering temperature and magnetic structure, despite the presence of a ferromagnetic impurity that dominated much of the measurements.</p> <p>The candidate's examination of the magnetism of the rock-salt oxides, Na2Cu2Te06 and Na3Cu2Sb06 has raised some controversy in the literature, as the exact nature of the one-dimensional order (either antiferromagnetic-antiferromagnetic or antiferromagnetic-ferromagnetic alternating linear chains) is uncertain. Again, theoretical calculations and comparison with other magnetic data can aide in the ultimate understanding of the overriding magnetism.</p> <p>This thesis has focused on the synthesis and study of transition metal oxides with interesting or unusual magnetic properties. In many cases, the compounds exhibited long-range magnetic order despite convoluted or non-existent magnetic superexchange pathways.</p> / Thesis / Doctor of Philosophy (PhD)