Teses / dissertações sobre o tema "Solar processes"
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Hassan, Ibrahim. "Solar energy conversion by photoelectrochemical processes". Thesis, University of Bath, 2011. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.542078.
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Stüwe, David [Verfasser], e Jan G. [Akademischer Betreuer] Korvink. "Inkjet processes for crystalline silicon solar cells". Freiburg : Universität, 2015. http://d-nb.info/1122646984/34.
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Kohn, Alexander Wolfe. "Modeling non-radiative processes in solar materials". Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/115806.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemistry, 2018.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 89-102).
In this thesis, we investigate methods and systems for understanding the electronic properties of a variety of systems relevant to organic photovoltaics. The second chapter examines how to predict the radiative and non-radiative decay rates of a large family of naphthalene derivatives. Naphthalene is a common building block in many organic electronic devices and possesses complex photophysics that are difficult to capture. Principally using time-dependent density functional theory, we are able to reproduce the experimental rates and, moreover, the fluorescence quantum yield, quite accurately. The next chapter then goes into extensions of the methodology discussed and analyzed in the prior chapter. Anthracene derivatives used for transferring triplet energy between a quantum dot and rubrene phase are found to have varying impacts on the total transfer efficiency based on the triplet lifetime of the anthracene derivative. Most potently, significant spin-orbit coupling in some of the derivatives causes substantial deactivation. An additional family, BODIPY dyes, is also investigated. They are found to undergo internal conversion gated by an excited-state conformational change, suggesting this may be a common motif. The fourth and fifth chapters investigate different interfacial effects and their impacts on the energy levels of electrons and holes in disordered organic devices. They look at specific systems: the interface between three different donors, PPV, P3HT, PTB7, and PCBM. They find that the interface can both reduce and induce disorder in different systems and that full treatment of the electronic environment is important for capturing accurate results. The final chapter investigates the use of neural networks to predict optimal range-separation parameters for density functionals.
by Alexander Wolfe Kohn.
Ph. D.
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Singletary, Steven J. (Steven James) 1973. "Igneous processes of the early solar system". Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/58444.
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Thesis (Ph. D. in Geochemistry)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, February 2004.Includes bibliographical references.
Experimental, petrographic and numerical methods are used to explore the igneous evolution of the early solar system. Chapters 1 and 2 detail the results of petrographic and experimental studies of a suite of primitive achondritic meteorites, the ureilites. The first chapter presents data that reveal correlations between mineral modal proportions and mineral chemistry that are used to guide experiments and models of ureilite petrogenesis. Chapter 2 details and applies the experimental results to describe ureilite petrogenesis as the result of progressive heating of a primitive carbon-rich body. The experiments place temperature and depth constraints on uteilite formation of 1100 to 13000C and 5 to 13 MPa - equivalent to the central pressure of an asteroid with a radius of 130 km. Chapter 3 reports the results of melting experiments of Allende carbonaceous chondrite at temperatures and pressures that would be expected on small bodies in the early solar system (up to 1300⁰C and 2.5 to 15 IPa) heated by decay of short lived isotopes. The results are then applied to ureilite petrogenesis and assembly of larger planetary bodies. The final chapter is an experimental study to test a hybridized source region for the high titanium lunar ultramafic glasses. Two models are presented that invoke either a heterogeneous source region or sinking and reaction of an ultramafic, titanium rich magma with underlying mantle regions.
by Steven J. Singletary.
Ph.D.in Geochemistry
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DELL'ORTO, ELISA CAMILLA. "Dye sensitized solar cells: materials and processes". Doctoral thesis, Università degli Studi di Milano-Bicocca, 2012. http://hdl.handle.net/10281/28476.
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During the thesis the DSSCs optimization was analyzed mainly through two strategies: the study of new sensitizers and the study
of alternatives materials for photo-cathode fabrication.
Two class of sensitizers were be analyzed: squaraine dyes and cyclometalated-based dyes. Then a study on dye-loading process will be presented, with implication in an industrialization process. For the photo-cathode fabrication two di erent materials were studied, a carbon based material and a polymeric material.
Then a part of the work concerned the study of devices analysis system. In particular electrochemical impedance spectroscopy was
studied to propose a new set up to analyze electric processes in different cell components.3
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Willes, Andrew James. "Coherent wave processes in solar and interplanetary plasmas". Thesis, The University of Sydney, 1996. https://hdl.handle.net/2123/27549.
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This thesis treats two aspects of coherent wave emission processes in space plasmas. Part I is concerned with the process of second harmonic plasma emission, as applied to solar radio type III bursts. Part II details a theory for simultaneous multiple frequency bands observed in solar microwave spike bursts, based on the electron-cyclotron maser mechanism.
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Steinfeld, Jeffrey I. "High-flux solar photon processes: opportunities for applications". MIT Energy Lab, 1992. http://hdl.handle.net/1721.1/27220.
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Jiménez, López Jesús. "Analysis of the Different Kinetic Processes in Perovskite Solar Cells". Doctoral thesis, Universitat Rovira i Virgili, 2019. http://hdl.handle.net/10803/668405.
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L'energia fotovoltaica s'ha convertit en una de les alternatives més populars com a font d'energia renovable. Es basa
en la transformació directa de radiació solar en electricitat. Es troba disponible a escala global i a més no necessita de
cap transformador per convertir l'energia mecànica en energia elèctrica, el que fa que sigui fàcil d'implementar. Avui en
dia, el material més utilitzat per a aplicacions fotovoltaiques segueix sent el silici. En canvi, el desenvolupament de
noves tecnologies, més barates, fàcils de processar i que a més poden utilitzar-se en substrats flexibles, ha sorgit com
a alternativa al silici. De totes elles, les perovskita basades en halurs de plom s'han convertit en una de les millors
opcions per a la comunitat científica a causa de les excel·lents propietats fotovoltaiques que presenta. Tot i que les
eficiències dels dispositius preparats amb perovskita han arribat al 25%, un valor que es troba molt proper al seu
màxim teòric, els processos que tenen lloc en aquests dispositius encara no són del tot coneguts. En aquesta tesi es
tracta d'obtenir informació sobre els processos dels transportadors de càrrega, des de com es generen fins a la
recombinació, tant en les interfícies com a l'interior del propi material. Per això, s'han utilitzat diferents tècniques de
caracterització avançades com el fotovoltatge transitori (TPV), la fotocorrent transitòria (TPC), l'extracció de càrrega
(CE) i l’espectroscòpia d'absorció transitòria en l'escala del femtosegon (FSTA), obtenint importants conclusions sobre
pèrdues i processos que afecten la recombinació de transportadors de càrrega que porten a pitjors eficiènciesLa energía fotovoltaica se ha convertido en una de las alternativas más populares como fuente de energía renovable. Se basa en la transformación directa de radiación solar en electricidad. Se encuentra disponible a escala global y además no precisa de ningún transformador para convertir la energía mecánica en energía eléctrica, lo que hace que sea fácil de implementar. Hoy en día, el material más utilizado para aplicaciones fotovoltaicas sigue siendo el silicio. En cambio, el desarrollo de nuevas tecnologías, más baratas, fáciles de procesar y que además pueden utilizarse en sustratos flexibles, ha surgido como alternativa al silicio. De todas ellas, las perovskitas basadas en haluros de plomo se han convertido en una de las mejores opciones para la comunidad científica debido a las excelentes propiedades fotovoltaicas que presenta. Aunque las eficiencias de los dispositivos preparados con perovskitas han alcanzado el 25%, un valor que se encuentra muy cercano a su máximo teórico, los procesos que tienen lugar en estos dispositivos aún no son del todo conocidos. En esta tesis se trata de obtener información acerca de los procesos de los transportadores de carga, desde cómo se generan hasta la recombinación, tanto en las interfaces como en el interior del propio material. Para ello, se han utilizado distintas técnicas de caracterización avanzadas como el fotovoltaje transitorio (TPV), fotocorriente transitoria (TPC), la extracción de carga (CE) y la espectrocopía de absorción transitoria en la escala del femtosegundo (fsTA), obteniendo importantes conclusiones sobre pérdidas
Photovoltaics have become one of the most popular renewable source of energy. Photovoltaic technologies transform sunlight into electricity, and they are also available worldwide, and they do not depend on the conversion of motive power, making this technology quite easy to implement. Nowadays, silicon is still the most used material for photovoltaics. Anyway, new photovoltaic technologies have emerged as alternatives to silicon, as they are cheaper, easier to process, and, they are possible to use on flexible substrates. Among them, lead halide perovskites have become one of the most popular choice in the scientific community, due to the great properties that this material presents. While efficiencies have risen above 25%, which is close to their maximum theoretical limit, there is still debate about the processes happening in the device. In this thesis, we try to gain insight into charge carrier processes from their generation to their recombination at both perovskite interfaces, and also in the bulk of the material. Using advanced characterization techniques, such as transient photovoltage (TPV), transient photocurrent (TPC), charge extraction (CE), and femtosecond transient absorption spectroscopy (fsTA) we obtained important findings about charge carrier losses, and artifacts affecting charge carrier recombination in functional devices that lead to lower power conversion efficiencies.
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Fitó, de la Cruz Jaume. "Solar-driven hybrid refrigeration systems based on thermochemical processes". Doctoral thesis, Universitat Rovira i Virgili, 2017. http://hdl.handle.net/10803/461061.
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Aquesta tesi doctoral proposa dos sistemes híbrids de refrigeració basats en energia solar en els quals l'element comú és un procés termoquímic: un sistema híbrid per absorció / termoquímic activat amb energia solar tèrmica de baixa temperatura (< 120 ºC), i un sistema híbrid per compressió / termoquímic activat amb energia solar fotovoltaica i calor residual.
El sistema per absorció / termoquímic és presentat en la seva configuració més simple i els seus components i condicions són discutits. Les prestacions del cicle són estimades de forma preliminar amb alguns parells de treball basats en amoníac, essent NH3/NaSCN i el NH3/BaCl2 dos d'interessants. La simulació preliminar del sistema híbrid mostra que aquest augmenta la fracció solar.
El sistema per compressió / termoquímic és definit i simulat en la fase d'acumulació de refrigerant assistida amb compressió. Un model de reacció quasi-estacionari de doble front, que pren en compte les limitacions de transferència de massa i de calor, és utilitzat per estudiar de forma preliminar la influència d'algunes condicions d'operació i paràmetres de disseny sobre la corba de reacció amb el parell amoníac / clorur de bari.
S'ha construit un dispositiu experimental per a obtenir dades experimentals de la fase d'acumulació de refrigerant assistida amb compressió, i confrontar aquestes dades amb les prediccions obtingudes del model de reacció de doble front, amb l'objectiu d'ajustar alguns dels paràmetres del model. Es conclou que el model ajustat prediu la corba de reacció amb una exactitud acceptable per a gairebé tots els experiments, amb petites discrepàncies.
S'espera que els sistemes híbrids proposats operin amb energia solar, siguin relativament compactes, emmagatzemin energia en menys volum d'emmagatzemament, i tinguin un petit grau d'autonomia (algunes hores dins d'un cicle d'operació diari). Aquests sistemes són interessants per a futurs estudis.Esta tesis doctoral propone dos sistemas híbridos de refrigeración basados en energía solar donde el elemento común es un proceso termoquímico: un sistema híbrido absorción / termoquímico activado con energía solar térmica de baja temperatura (< 120 ºC), y un sistema híbrido compresión / termoquímico activado con energía solar fotovoltaica y calor residual. El sistema absorción / termoquímico es presentado en su configuración más simple y sus componentes y condiciones de operación discutidas. El desempeño del ciclo es estimado preliminarmente con algunos pares de trabajo con amoníaco, con NH3/NaSCN y NH3/BaCl2 como pares interesantes. La simulación preliminar del sistema híbrido muestra que este aumenta la fracción solar. El sistema compresión / termoquímico es definido y simulado en la fase de acumulación de refrigerante asistida con compresión. Un modelo de reacción cuasi-estacionario de doble frente, que tiene en cuenta limitaciones de transferencia de masa y de calor, es usado para estudiar preliminarmente la influencia de algunas condiciones de operación y parámetros de diseño sobre la curva de reacción con el par amoníaco / cloruro de bario. Se ha construido un dispositivo experimental para obtener datos experimentales de la fase de acumulación de refrigerante asistida con compresor, y confrontar estos datos con las predicciones obtenidas del modelo de reacción de doble frente, con el objetivo de ajustar algunos parámetros del modelo. Se concluye que el modelo ajustado predice la curva de reacción con exactitud aceptable para casi todos los experimentos, con pequeñas discrepancias. Se espera que los sistemas híbridos propuestos operen con energía solar, sean relativamente compactos, almacenen energía en menor volumen, y tengan un pequeño grado de autonomía (unas pocas horas en un ciclo de operación diario). Estos sistemas son interesantes para futuros estudios.
This doctoral thesis proposes two solar-based hybrid refrigeration systems where the central piece is a thermochemical process: an absorption / thermochemical hybrid system driven by low-grade solar thermal energy (< 120 ºC), and a compression / thermochemical hybrid refrigeration system driven by solar-PV energy and waste heat. The absorption / thermochemical hybrid system is presented in its most simple configuration, and its components and operating conditions discussed. A preliminary performance estimation is carried out with some ammonia-based working pairs finding the NH3/NaSCN and NH3/BaCl2 as interesting working pairs. A preliminary simulation of the hybrid system shows that it increases the solar coverage. The compression / thermochemical hybrid system is also defined and simulated in its refrigerant storage phase assisted with compression. A 2-front quasi-steady reaction model which accounts for heat and mass transfer limitations is used to preliminarily study the influence of some operating conditions and design parameters on the system’s reaction curve with the NH3/BaCl2 working pair. An experimental setup has been built to obtain experimental data from the compression-assisted refrigerant storage phase, and confront this data with the predictions obtained from the 2-front reaction model, with the objective of adjusting some parametres of the model. It is concluded that the adjusted model predicts the reaction curve with acceptable accuracy for almost all experiments, with small discrepancies. The proposed hybrid systems are expected to operate with solar energy, be relatively compact, store energy with reduced storage volume, and have a small degree of autonomy (a few hours within a daily operating cycle). These systems are promising for further study.
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Vocks, Christian. "Electron kinetic processes in the solar corona and wind". Thesis, Universität Potsdam, 2012. http://opus.kobv.de/ubp/volltexte/2013/6525/.
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The Sun is surrounded by a 10^6 K hot atmosphere, the corona. The corona and the solar wind are fully ionized, and therefore in the plasma state. Magnetic fields play an important role in a plasma, since they bind electrically charged particles to their field lines. EUV spectroscopes, like the SUMER instrument on-board the SOHO spacecraft, reveal a preferred heating of coronal ions and strong temperature anisotropies. Velocity distributions of electrons can be measured directly in the solar wind, e.g. with the 3DPlasma instrument on-board the WIND satellite. They show a thermal core, an anisotropic suprathermal halo, and an anti-solar, magnetic-field-aligned, beam or "strahl".
For an understanding of the physical processes in the corona, an adequate description of the plasma is needed. Magnetohydrodynamics (MHD) treats the plasma simply as an electrically conductive fluid. Multi-fluid models consider e.g. protons and electrons as separate fluids. They enable a description of many macroscopic plasma processes. However, fluid models are based on the assumption of a plasma near thermodynamic equilibrium. But the solar corona is far away from this. Furthermore, fluid models cannot describe processes like the interaction with electromagnetic waves on a microscopic scale.
Kinetic models, which are based on particle velocity distributions, do not show these limitations, and are therefore well-suited for an explanation of the observations listed above. For the simplest kinetic models, the mirror force in the interplanetary magnetic field focuses solar wind electrons into an extremely narrow beam, which is contradicted by observations. Therefore, a scattering mechanism must exist that counteracts the mirror force. In this thesis, a kinetic model for electrons in the solar corona and wind is presented that provides electron scattering by resonant interaction with whistler waves.
The kinetic model reproduces the observed components of solar wind electron distributions, i.e. core, halo, and a "strahl" with finite width. But the model is not only applicable on the quiet Sun. The propagation of energetic electrons from a solar flare is studied, and it is found that scattering in the direction of propagation and energy diffusion influence the arrival times of flare electrons at Earth approximately to the same degree.
In the corona, the interaction of electrons with whistler waves does not only lead to scattering, but also to the formation of a suprathermal halo, as it is observed in interplanetary space. This effect is studied both for the solar wind as well as the closed volume of a coronal magnetic loop.
The result is of fundamental importance for solar-stellar relations. The quiet solar corona always produces suprathermal electrons. This process is closely related to coronal heating, and can therefore be expected in any hot stellar corona.
In the second part of this thesis it is detailed how to calculate growth or damping rates of plasma waves from electron velocity distributions. The emission and propagation of electron cyclotron waves in the quiet solar corona, and that of whistler waves during solar flares, is studied. The latter can be observed as so-called fiber bursts in dynamic radio spectra, and the results are in good agreement with observed bursts.Die Sonne ist von einer 10^6 K heißen Atmosphäre, der Korona, umgeben. Sie ist ebenso wie der Sonnenwind vollständig ionisiert, also ein Plasma. Magnetfelder spielen in einem Plasma eine wichtige Rolle, da sie elektrisch geladene Teilchen an ihre Feldlinien binden. EUV-Spektroskope, wie SUMER auf der Raumsonde SOHO, zeigen eine bevorzugte Heizung koronaler Ionen sowie starke Temperaturanisotropien. Geschwindigkeitsverteilung von Elektronen können im Sonnenwind direkt gemessen werden, z.B. mit dem 3DPlasma Instrument auf dem Satelliten WIND. Sie weisen einen thermischen Kern, einen isotropen suprathermischen Halo, sowie einen anti-solaren, magnetfeldparallelen Strahl auf. Zum Verständnis der physikalischen Prozesse in der Korona wird eine geeignete Beschreibung des Plasms benötigt. Die Magnetohydrodynamik (MHD) betrachtet das Plasma einfach als elektrisch leitfähige Flüssigkeit. Mehrflüssigkeitsmodelle behandeln z.B. Protonen und Elektronen als getrennte Fluide. Damit lassen sich viele makroskopische Vorgänge beschreiben. Fluidmodelle basieren aber auf der Annahme eines Plasmas nahe am thermodynamischen Gleichgewicht. Doch die Korona ist weit davon entfernt. Ferner ist es mit Fluidmodellen nicht möglich, Prozesse wie die Wechselwirkung mit elektromagnetischen Wellen mikroskopisch zu beschreiben. Kinetische Modelle, die Geschwindigkeitsverteilungen beschreiben, haben diese Einschränkungen nicht und sind deshalb geeignet, die oben genannten Messungen zu erklären. Bei den einfachsten Modellen bündelt die Spiegelkraft im interplanetaren Magnetfeld die Elektronen des Sonnenwinds in einen extrem engen Strahl, im Widerspruch zur Beobachtung. Daher muss es einen Streuprozess geben, der dem entgegenwirkt. In der vorliegenden Arbeit wird ein kinetisches Modell für Elektronen in der Korona und im Sonnenwind präsentiert, bei dem die Elektronen durch resonante Wechselwirkung mit Whistler-Wellen gestreut werden. Das kinetische Modell reproduziert die beobachteten Bestandteile von Elektronenverteilungen im Sonnenwind, d.h. Kern, Halo und einen Strahl endlicher Breite. Doch es ist nicht nur auf die ruhige Sonne anwendbar. Die Ausbreitung energetischer Elektronen eines solaren Flares wird untersucht und dabei festgestellt, dass Streuung in Ausbreitungsrichtung und Diffusion in Energie die Ankunftszeiten von Flare-Elektronen bei der Erde in etwa gleichem Maße beeinflussen. Die Wechselwirkung von Elektronen mit Whistlern führt in der Korona nicht nur zu Streuung, sondern auch zur Erzeugung eines suprathermischen Halos, wie er im interplanetaren Raum gemessen wird. Dieser Effekt wird sowohl im Sonnenwind als auch in einem geschlossenen koronalen Magnetfeldbogen untersucht. Das Ergebnis ist von fundamentaler Bedeutung für solar-stellare Beziehungen. Die ruhige Korona erzeugt stets suprathermische Elektronen. Dieser Prozeß ist eng mit der Koronaheizung verbunden, und daher in jeder heißen stellaren Korona zu erwarten. Im zweiten Teil der Arbeit wird beschrieben, wie sich aus der Geschwindigkeitsverteilung der Elektronen die Dämpfung oder Anregung von Plasmawellen berechnen lässt. Die Erzeugung und Ausbreitung von Elektronenzyklotronwellen in der ruhigen Korona und von Whistlern während solarer Flares wird untersucht. Letztere sind als sogenannte fiber bursts in dynamischen Radiospektren beobachtbar, und die Ergebnisse stimmen gut mit beobachteten Bursts überein.
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ORLANDI, Michele. "PHOTOINDUCED PROCESSES IN SUPRAMOLECULAR SYSTRMS FOR SOLAR ENERGY CONVERSION". Doctoral thesis, Università degli studi di Ferrara, 2010. http://hdl.handle.net/11392/2389170.
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Artificial photosynthesis, defined as the conversion of solar energy into fuels, could
provide a solution to the problem of the intermittent avalaibility of sunlight, one of the key
issues to overcome in order to implement widespread use of solar energy. Among the
possible applications of artificial photosynthesis, particularly interesting are photochemical
water splitting, since it represents a possible way to solar hydrogen generation, and the
photocatalytic reduction of CO2 to CO, HCOOH, CH3OH or CH4, important industrial
intermediates or fuels.
In a biomimetic approach, a generic artificial photosynthetic device consists of an
antenna system, a charge-separating reaction center, an oxidation catalyst and a reduction
catalyst. Antenna systems absorb visible photons, thus converting them to electronic
excitation energy which is then conveyed via energy transfer processes to the reaction center
where it drives electron transfer processes leading to charge separation. The photogenerated
electrons and holes provide to the catalysts the oxidizing and reducing equivalents necessary
to drive redox reactions on a substrate.
In this work, a number of systems proposed as possible components of an artificial
photosynthetic device or as models for the investigation of related key processes are studied.
The systems described here are designed organizing molecular components in spatially
defined architectures, following the principles of supramolecular chemistry.
In particular, Chapter 3 describes a triad for charge-separation obtained by selfassembling
of a Ru-porphyrin electron donor, an Al-porphyrin as the photoexcitable
chromophore and a naphtalenebisimide electron acceptor. The intrinsically asymmetric
nature of triad systems required the development of assembling strategies based on
molecular recognition between the subunits, implemented exploiting highly selective metalligand
interactions. Photoinduced charge-separation was demostrated by a detailed
photophysical and electrochemical characterization.
In Chapter 4, a Sn-porphyrin component and a Ru-porphyrin component are
combined in a series of tri-, penta- and heptanuclear supramolecular arrays. A number of
photoinduced intercomponent electron-transfer processes, leading to a common chargeseparated
state, could be identified by use of time-resolved UV-Vis absorption and emission
spectroscopy and their kinetics rationalized in terms of standard electron-transfer theory.
Chapter 5 describes a model complex of the [FeFe] hydrogenase enzyme active site,
tested as a reduction catalyst for photochemical hydrogen production. High turnover
numbers were obtained in a photocatalytic cycle using Ru(bpy)3
2+ as photosensitizer and
ascobic acid as sacrificial electron donor.
In Chapter 6, a kinetic study on [Ru4(μ-O)4(-OH)2(H2O)4(γ-SiW10O36)2]10-, a
recently proposed Ruthenium Polyoxometalate catalyst for the oxygen-evolving side of
water splitting, is presented. Hole transfer from photogenerated oxidants to the catalyst has
been investigated by means of nanosecond laser flash photolysis, both in solution and at a
sensitized TiO2 surface. The very fast rates observed open the possibility to include [Ru4(μ-
O)4(-OH)2(H2O)4(γ-SiW10O36)2]10- in photochemical water splitting devices.
Chapter 7 describes the photophysical investigation of supramolecular systems
containing a Zn-porphyrin chromophore and the [fac-Re(CO)3(bpy)]+ fragment as
components. Polypyridine-Re(I)-tricarbonyl complexes are known to catalyze CO2
reduction, opening the possibility to exploit them for photocatalysis. The results obtained
provided guidelines for the realization of new adducts to be tested in photocatalytic cycles.
A side-project in the field of molecular electronics is also reported in Chapter 8.
Photoinduced electron transfer is demonstrated here as the working principle of a prototype
photochromic switch for non-destructive read-out optical memory systems. The system
proposed is composed of a diarylethene as photochromic unit and a perylene bisimide as
fluorophore.
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Al-Hasnawi, Hassan. "Solar Heat in Industrial Processes : Integration of Parabolic Trough Solar Collectors Dairy Plants and Pharmaceutical Plants". Thesis, Umeå universitet, Institutionen för tillämpad fysik och elektronik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-125025.
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The industry sector accounts for a high share of the final energy consumption, with industries in EU-28accounting for a quarter of the final energy demand. Studies also show that 45 % of the industrial heatdemand in EU-27 is in a temperature range that can be supplied with present day solar collectors. Despitethis large potential, solar heat faces obstacles hindering its growth in the industrial sector. The mostsignificant obstacle is the low insight of the industrial system designs and energy demands. Those arecrucial factors for the feasibility and dimensioning of solar heating systems. Three case studies aretherefore conducted in dairy and pharmaceutical plants in order to review the most promising integrationpoints for parabolic trough solar collectors in terms of annual heat demand, temperature level andintegration effort. Two case studies are performed in dairy plants and one in a pharmaceutical plant, alllocated in Sweden. The analyses comprised reviewing energy mappings, process and instrumentationdiagrams of processes and boiler systems, and hourly energy demand data. Simulations have beencarried out with Polysun for the processes with hourly energy data available.Four integration points have been determined to be high priority solar heat integration points in dairyplants, when considering annual thermal energy demand, temperature levels and integration effort.Those are the low pressure steam line, heating of feedwater, clean in place systems and pasteurizers.Solar heat integration concepts have been presented for all the aforementioned heat sinks andsimulations have been conducted for the low pressure steam line and heating of feedwater. A significantamount of excess heat is produced as a result of fluctuating heat demands and peak solar heat productionhours. Further investigation should be carried out, in order to review the potential of supplying excessheat to other heat sinks. Despite the reviewed potential of the clean in place systems and pasteurizers,lack of the hourly energy demand has hindered further analyses of those systems. It is thereforerecommended to conduct energy measurements before taking further measures.Two integration points have been identified in the pharmaceutical plant, namely autoclaves andmultiple-effect distillers. Solar steam generation concepts have been presented for both processes. Theautoclaves are provided with 4,5 bar steam intermittently, as they work with batches and can have ondutyand off-duty intervals ranging from 3-30 minutes. The multiple-effect distillers are providedwith 7 bar steam, which is of rather high pressure for the solar collectors model on which thesimulations are based. The heat demand of the distillers is more or less constant.It was generally easier to acquire data for the integration points at the supply level. For instance, all heatsinks at the supply level had energy demand data available, contrary to the process level. This inclinesadditional focus on integration to the supply level, if the extent of the feasibility study is to be kept to aminimum.
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Shapiro, Alexander I. "Molecular processes and turbulent magnetic fields in the solar atmosphere /". Zürich : ETH, 2008. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17961.
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Fredin, Kristofer. "Studies of Charge Transport Processes in Dye-sensitized Solar Cells". Doctoral thesis, KTH, Kemi, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4430.
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Dye-sensitized solar cells (DSCs) have attained considerable attention during the last decade because of the potential of becoming a low cost alternative to silicon based solar cells. Although efficiencies exceeding 10% in full sunlight have been presented, major improvements of the system are however limited. Electron transport is one of the processes in the cell and is of major importance for the overall performance. It is further a complex process because the transport medium is a mesoporous film and the pores are completely filled by an electrolyte with high ionic strength, resulting in electron-ion interactions. Therefore, present models describing electron transport include simplifications, which limit the practical use, in terms of improving the DSC, because the included model parameters usually have an effective nature. This thesis focuses in particular on the influence of the mesoporous film on electron transport and also on the influence of electron-ion interactions. In order to model diffusion, which is assumed to be the transport process for electrons in the DSC, Brownian motion simulations were performed and spatial restrictions, representing the influence of the mesoporous film, were introduced by using representative models for the structure. The simulations revealed that the diffusion coefficient is approximately half the value for electrons and ions in mesoporous systems. To study the influence of ions, a simulation model was constructed in where electric fields were calculated with respect to the net charge densities, resulting from the different charge carrier distributions. The simulations showed that electron transport is highly dependent on the nature of the ions, supporting an ambipolar diffusion transport model. Experimentally, it was found that the transport process is dependent on the wavelength of the incident light; we found that the extracted current was composed of two components for green light illumination, one fast and one slow. The slow component showed similar trends as the normal current. Also we found that the transport coefficient scaled linearly with film thickness for a fixed current, which questions diffusion as transport process. Other experiments, investigating various effects in the DSC, such as the effect of different cations in the electrolyte, are also presented.QC 20100708
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Fredin, Kristoffer. "Studies of charge transport processes in dye-sensitized solar cells /". Stockholm : KTH Chemical Science and Engineering, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4430.
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Xu, He. "Laboratory studies on dynamical processes in salinity-gradient solar pond /". The Ohio State University, 1990. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487677267731063.
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Lisco, Fabiana. "High rate deposition processes for thin film CdTe solar cells". Thesis, Loughborough University, 2015. https://dspace.lboro.ac.uk/2134/17965.
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This thesis describes the development of a fast rate method for the deposition of high quality CdS and CdTe thin films. The technique uses Pulsed DC Magnetron Sputtering (PDCMS). Surprisingly, the technique produces highly stable process conditions. CREST is the first laboratory worldwide to show that pulsed DC power may be used to deposit CdS and CdTe thin films. This is a very promising process technology with potential for eventual industrial deployment. The major advantage is that the process produces high deposition rates suitable for use in solar module manufacturing. These rates are over an order of magnitude faster than those obtained by RF sputtering. In common with other applications it has also been found that the energetics of the pulsed DC process produce excellent thin film properties and the power supply configuration avoids the need for complex matching circuits. Conventional deposition methodologies for CdS, Chemical Bath Deposition (CBD) and CdTe thin films, Electrodeposition (ED), have been chosen as baselines to compare film properties with Pulsed DC Magnetron Sputtering (PDCMS). One of the issues encountered with the deposition of CdS thin films (window layers) was the presence of pinholes. A Plasma cleaning process of FTO-coated glass prior to the deposition of the CdS/CdTe solar cell has been developed. It strongly modifies and activates the TCO surface, and improves the density and compactness of the deposited CdS thin film. This, in turn, improves the optical and morphological properties of the deposited CdS thin films, resulting in a higher refractive index. The pinhole removal and the increased density allows the use of a much thinner CdS layer, and this reduces absorption of blue spectrum photons and thereby increases the photocurrent and the efficiency of the thin film CdTe cell. Replacing the conventional magnetic stirrer with an ultrasonic probe in the chemical bath (sonoCBD) was found to result in CdS films with higher optical density, higher refractive index, pinhole and void-free, more compact and uniform along the surface and through the thickness of the deposited material. PDCMS at 150 kHz, 500 W, 2.5 μs, 2 s, results in a highly stable process with no plasma arcing. It allows close control of film thickness using time only. The CdS films exhibited a high level of texture in the <001> direction. The grain size was typically ~50 nm. Pinholes and voids could be avoided by reducing the working gas pressure using gas flows ii below 20 sccm. The deposition rate was measured to be 1.33 nm/s on a rotating substrate holder. The equivalent deposition rate for a static substrate is 8.66 nm/s, which is high and much faster than can be achieved using a chemical bath deposition or RF magnetron sputtering. The transmission of CdS can be improved by engineering the band gap of the CdS layer. It has been shown that by adding oxygen to the working gas pressure in an RF sputtering deposition process it is possible to deposit an oxygenated CdS (CdS:O) layer with an improved band gap. In this thesis, oxygenated CdS films for CdTe TF-PV applications have been successfully deposited by using pulsed DC magnetron sputtering. The process is highly stable using a pulse frequency of 150 kHz and a 2.5 μs pulse reverse time. No plasma arcing was detected. A range of CdS:O films were deposited by using O2 flows from 1 sccm to 10 sccm during the deposition process. The deposition rates achieved using pulsed DC magnetron sputtering with only 500 W of power to the magnetron target were in the range ~1.49 nm/s ~2.44 nm/s, depending on the oxygen flow rate used. The properties of CdS thin films deposited by pulsed DC magnetron sputtering and chemical bath deposition have been studied and compared. The pulsed DC magnetron sputtering process produced CdS thin films with the preferred hexagonal <001> oriented crystalline structure with a columnar grain growth, while sonoCBD deposited films were polycrystalline with a cubic structure and small grainy crystallites throughout the thickness of the films. Examination of the PDCMS deposited CdS films confirmed the increased grain size, increased density, and higher crystallinity compared to the sonoCBD CdS films. The deposition rate for CdS obtained using pulsed DC magnetron sputtering was 2.86 nm/s using only 500 W power on a six inch circular target compared to the much slower (0.027 nm/s) for the sonoChemical bath deposited layers. CdTe thin films were grown on CdS films prepared by sonoCBD and Pulsed DC magnetron sputtering. The results showed that the deposition technique used for the CdS layer affected the growth and properties of the CdTe film and also determined the deposition rate of CdTe, being 3 times faster on the sputtered CdS. PDCMS CdTe layers were deposited at ambient temperature, 500 W, 2.9 μs, 10 s, 150 kHz, with a thickness of approximately 2 μm on CdS/TEC10 coated glass. The layers appear iii uniform and smooth with a grain size less than 100 nm, highly compact with the morphology dominated by columnar grain growth. Stress analysis was performed on the CdTe layers deposited at room temperature using different gas flows. Magnetron sputtered thin films deposited under low gas pressure are often subject to compressive stress due to the high mobility of the atoms during the deposition process. A possible way to reduce the stress in the film is the post-deposition annealing treatment. As the lattice parameter increased; the stress in the film is relieved. Also, a changing the deposition substrate temperature had an effect on the microstructure of CdTe thin films. Increasing the deposition temperature increased the grain size, up to ~600 nm. CdTe thin films with low stress have been deposited on CdS/TEC10 coated glass by setting the deposition substrate temperature at ~200°C and using high argon flows ~ 70 sccm Ar. Finally, broadband multilayer ARCs using alternate high and low refractive index dielectric thin films have been developed to improve the light transmission into solar cell devices by reducing the reflection of the glass in the extended wavelength range utilised by thin-film CdTe devices. A four-layer multilayer stack has been designed and tested, which operates across the wavelength range used by thin-film CdTe PV devices (400 850 nm). Optical modelling predicts that the MAR coating reduces the WAR (400-850 nm) from the glass surface from 4.22% down to 1.22%. The application of the MAR coating on a thin-film CdTe solar cell increased the efficiency from 10.55% to 10.93% or by 0.38% in absolute terms. This is a useful 3.6% relative increase in efficiency. The increased light transmission leads to improvement of the short-circuit current density produced by the cell by 0.65 mA/cm2. The MAR sputtering process developed in this work is capable of scaling to an industrial level.
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Brienza, Monica. "Solar Advanced Oxidation Processes for removing emerging contaminants in wasterwater". Thesis, Perpignan, 2015. http://www.theses.fr/2015PERP0001.
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Les usines de traitement des eaux usées ne sont pas prévues pour traiter les polluants émergeants, substances organiques, tels des résidus de médicament, des produits phytosanitaires ou des hormones. Par conséquent, elles sont la source principale d’émission de micropolluants récalcitrants dans l’environnement. La Directive DCE 2000/60/CE demande un "bon statu chimique et biologique” de tous les plans d'eau d'ici 2015. L’objectif principal de cette thèse de doctorat a été d’adopter une méthode respectueuse de l’environnement pour traiter ces polluants. La méthode choisie est basée sur le processus d’oxydation avancée (POA). Elle se base sur la génération par voie solaire, et in situ, d’espèces radicalisées hautement réactives (HO● et/ou SO4-), en se focalisant sur la photocatalyse hétérogène et homogène. Les performances de l'POA ont été évaluées en comparant les taux de dégradation et/ou reminéralisassions des micropolluants. Ce critère a été complété par l'identification des sous-produits, de ses transformations associés et de mesures de toxicité. A cet effet, des tests standards d'écotoxicité ainsi que d'activité oestrogénique ont été réalisés, par la méthode toxicologique ISO ou par le test spécifique inhérent au contrôle de l’activité oestrogénique des eaux usées. Les technologies basées sur les processus d’oxydation avancée par voie solaire peuvent être des méthodes prometteuses de traitement des eaux usées. Toutes les molécules testées sont systématiquement dégradées, même celles présentes à de basses concentrations. La compatibilité environnementale a systématiquement été améliorée. L’irrigation des cultures en réutilisant des eaux usées devient possibleWastewater effluents are the major source of micropollutants in the environment. These recalcitrant compounds that can be escape from wastewater treatment plant (WWTP) are called emerging contaminants. It is necessary to improve the efficiency of wastewater treatment plants. In fact, Water Framework Directive required a “good chemical and biological status” of all water bodies until 2015. The major aim of the dissertation was to contribute to improve the evaluation of solar advanced oxidation processes, and more specifically heterogeneous and homogeneous photocatalysis, for removing emerging contaminants from wastewater effluents. In this objective, the efficiency of AOPS was not only evaluated with the degradation and/or mineralization rates of the micropollutants. This necessary criterion was completed with the identification of the by-products and the associated transformation pathways, but also with toxicity measurements. This last point was explored with standard ecotoxicity tests and also estrogenic activity that represent a specific test relevant to characterize an identified risk associated to the discharge of effluents into the environment.All the experimental results obtained during this dissertation tends to demonstrate that solar advanced oxidation processes has the potential to open new feasible remediation strategies for WWTPs effluent tertiary treatment before wastewater reuse in irrigation for instance. All the tested molecules have systematically been degraded, high number of micro-organic pollutants initially presented in a mixture were removed even at very low concentration, environmental compatibility is systematically improved
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Ozgurel, Ozge. "Modeling the chemical trapping processes in the outer solar system". Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066226/document.
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Ce projet a pour but de répondre à quelques questions pendantes de planétologie en utilisant des méthodes de chimie quantique. Il recouvre principalement deux études.La première étude modélise les processus chimiques susceptibles d’expliquer la déplétion en gaz rares observée dans l’atmosphère de Titan par la mission Huygens ; l’étude considère la formation par association radiative, des complexes stables entre Ar, Kr, Xe et H3+ ou les ions protonés, ceci dans la nébuleuse proto-planétaire, avant la formation de Titan en tant qu’objet.La seconde étude analyse les mécanismes piégeant les volatiles dans les glaces, mécanismes à l’œuvre dans les comètes comme dans la lune Europe. Les scénarios d’une origine primordiale commune de O2 et S2 observés dans la comète 67P/C-G lors de la mission ROSETTA, ont pu être validés, donnant des rapports d’abondance avec l’eau proches des observations, et proposant une explication pour la corrélation/non corrélation avec l’eau pour les deux espèces. De même, un scénario pour l’origine des éléments mineurs Na et K détectés dans l’exosphère d’Europe, satellite pour lequel l’intérêt a ressurgi en raison des missions à venir, Juice de l’ESA et Europa Clipper de la NASA, a été étudié et s’est révélé valable également pour Mg et Ca pour lesquels des prédictions d’abondance ont été faites. Du point de vue des simulations numériques, ce travail combine deux approches ab-initio, une approche moléculaire pour la phase gazeuse du premier cas et une approche périodique du solide pour les autres casThis project aims at answering some questions in planetology by means of ab-inito quantum chemistry. It can be divided into two main studies. One models the chemical processes likely to explain the noble gases deficiency observed by the Huygens probe in the atmosphere of Titan; it investigates the formation of stable complexes between Ar, Kr, Xe and H3+ or protonated ions by radiative association, in the proto-solar nebula, prior to the formation of Titan. The other analyzes the trapping mechanisms of volatiles in the ice at work in comets as well as in Europa. Scenarios of primordial origin for O2 and S2, observed in comet 67P/C-G by the ROSETTA probe, were thus validated, giving abundance ratios with H2O close to those observed and proposing an explanation for the respective correlation/non-correlation with water of the two species. Also, a scenario for the origin of trace elements Na, K detected in the exosphere of Europa whose interest is revived by anticipating the missions Juice and Europa Clipper, was argumented and found available for Mg and Ca to predict relative abundancies to be observed. The computational work combines two ab-inito approaches, molecular calculations in gaseous phase in the first case and periodic solid state calculations in the second
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RAZZA, STEFANO. "Development of fabrication processes for large area perovskite solar cells". Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2014. http://hdl.handle.net/2108/202974.
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Al-Thani, Faleh N. "Economical desalination processes in Qatar". Thesis, University of Hertfordshire, 2002. http://hdl.handle.net/2299/14043.
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The limited underground water resources and the dramatic increase of fresh water consumption in Qatar forced the government to seek alternative ways to compensate for the lack of fresh water resources. Unfortunately, most of the currently available alternatives are costly in terms of excessive fuel consumption; also they require large capital investment and high maintenance cost. Such plants currently produce over 98% of the total fresh water in Qatar. This ratio may increase to 100% in the next few years. The main aim of this work is to investigate the most viable water desalination processes, which can produce sufficient, and a continuous supply of fresh water with low operation and construction costs. Climatic conditions and solar radiation in Qatar have been studied and analysed to determine the performance of any potential solar system applicable to this country. A technical and economical investigation into the current and common desalination methods with particular emphasis on the three main desalination systems including multistage flash, multiple effect distillation and reverse osmosis were conducted and included. A comprehensive literature survey on various water desalination methods was undertaken. The current experimental program was confined mainly to one novel type of tilted tray solar still system, namely pyramid tilted tray solar still, which was developed to increase productivity by increasing the receiving surface area of the still (the absorber) in order to collect the optimum amount of solar radiation. Two types of cover have also been selected and tested in this work, namely pyramid and dome shapes. These tilted tray solar stills were designed and constructed on a small scale and have been tested under controlled laboratory conditions at the University of Hertfordshire. Various parameters, which are likely to effect the still performance have been investigated. These include water flow rate, spacing between cover and tray surface, glass thickness, insulation layer, and inlet water temperature. Finally, a comparison of the stills performance characteristics of the two shapes has been carried out. The laboratory experimental results of hourly production revealed that pyramid type solar still yield higher distilled water output results than the dome type. However, the use of the pyramid shape with tilted tray solar can lead to further increase in the still productivity by optimising the orientation and surface area of the still absorber. The field experimental results of pyramid solar still, which were conducted under local climate conditions of Qatar, indicated clearly that solar desalination can be a suitable economical option, particularly for remote areas, where the fresh water demand is low and water transport is expensive. Moreover, a theoretical model was employed to predict the effects on solar still performance under three various parameters under typical climatic conditions of Qatar; These include the thermal insulation layer, the water depth and wind speed. Due to the economical reasons the dual-purpose multistage flash process will remain for the foreseeable future the preferred process, when fresh water and electricity demands are growing concurrently and rapidly.
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Al-Edhari, Ali Jaber. "Complex organic molecules in solar-type star forming regions". Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAY048/document.
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Le but de la présente thèse est l'étude de la compléxité moléculaire dans les régions de formation stellaires. Cette thèse s'axe sur deux classes de molécule aux caractéristiques prébiotiques : les molécules organiques complexes et les cyanopolyynes.Dans ce contexte, j'ai analysé des données d'un seul échantillon de relevés spec- traux en exploitant des codes de transfert radiatif à l'équilibre thermodynamique local (LTE) et/ou non-LTE pour deux sources : une proto-étoile de type solaire dans un environnement calme (IRAS 16293-2422) et un proto-ama constitué de proto-étoile de type solaire (OMC2-FIR4).L'objectif est de trouver des similar- ités et des différences entre ces deux cas.J'ai utilisé des données issu de deux relevés spectraux : TIMASSS (The IRAS16293-2422 Millimeter And Submilimeter Spectral Survey) réalisés en 2011 (Caux et al. 2011), et ASAI(Astrochemical Surveys At IRAM) réalisés pen- dant la période 2013-2015 (eg Lopez-Sepulcre et al.2015). J'ai extrais les lignes (identification et intensité intégrée) en utilisant le paquet disponible publique- ment : CASSIS (Centre d'Analyse Scientifique de Spectres Infrarouges et Sub- millimetrique). Pour finir, j'ai utilisé le paquet GRAPES (GRenoble Analysis of Protostellar Envelope Spectral) afin de modéliser la distribution spectrale énergétique de ligne (SLED) des molécules détectées, mais aussi afin d'estimer leurs abondances à travers l'envelope de IRAS16293 et du coeur chaud OMC2- FIR4.Les principaux résultats de la thèse sont :1. Le premier recensement complet des molecules organiques complexes (COMs) dans IRAS162932. La première détéction de COMs dans l'enveloppe froide d'une proto-étoile de type solaire (IRAS16293-2422) supportant l'idée qu'un méchanisme de formation, relativement efficace pour les COMs détectées, doit exister en phase gazeuse froide.3. La découverte d'une fine corrélation entre le diméthyle-éther (DME) et le méthyle-formate (MF) suggère une relation mère fille entre ces deux espèces.4. La detection de formamide, espèce avec un très fort potentiel prébiotique, dans plusieurs protoétoiles incluant IRAS16293-2422 et OMC2-FIR4.5. Le recensement complet des cyanopolyynes dans IRAS16293 et OMC2- FIR4 avec la détection de HC3N, HC5N, DC3N et pour OMC2-FIR4: le C13 isotopologue du HC3N cyanopolyynes.Ces résultats sont le sujet principal de deux publications (Jaber et al.2014, ApJ; Lopez-Sepulcre, Jaber et al.2015,MNRAS), un article accepté (Jaber et al., A & A) et un article à soumettre (Jaber et al. A & A)The present PhD thesis goal is the study of the molecular complexity in solar type star forming regions. It specifically focuses on two classes of molecules with a pre-biotic value, the complex organic molecules and the cyanopolyynes.At this scope, I analyzed data from single-dish spectral surveys by means of non-LTE or/and non-LTE radiative transfer codes in two sources, a solar type protostar in an isolated and quiet environment (IRAS16293-2422) and a proto-cluster of solar type protostars (OMC2-FIR4). The goal is to find similarities and differences between these two cases.I used data from two spectra surveys: TIMASSS (The IRAS16293-2422 Millimeter And Submillimeter Spectral Survey), which has been carried out in 2011 (Caux et al. 2011), and ASAI (Astrochemical Surveys At IRAM), which has been carried out in 2013-2015 (e.g. Lopez-Sepulcre et al. 2015).I extracted the lines (identification and integrated intensity) by means of the publicly available package CASSIS (Centre dAnalyse Scientifique de Spectres Infrarouges et Submillimtriques).Finally, I used the package GRAPES (GRenoble Analysis of Protostellar Envelope Spectra) to model the Spectral Line Energy Distribution (SLED) of the detected molecules, and to estimate their abundance across the envelope and hot corino of IRAS16293-2422 and OMC2-FIR4, respectively.The major results of the thesis are:1) The first full census of complex organic molecules (COMs) in IRAS16293-2422;2) The first detection of COMs in the cold envelope of a solar type protostar (IRAS16293-2422), supporting the idea that a relatively efficient formation mechanism for the detected COMs must exist in the cold gas phase;3) The discovery of a tight correlation between the dimethyl ether (DME) and methyl format (MF), suggesting a mother-daughter relationship;4) The detection of formamide, a species with a very high pre-biotic value, in several protostars, included IRAS16293-2422 and OMC2-FIR4;5) The full census of the cyanopolyynes in IRAS16293-2422 and OMC2-FIR4, with the detection of HC3N and HC5N, DC3N and, for OMC2-FIR4, the 13C isotopologue of HC3N cyanopolyynes.These results are the focus of two published articles (Jaber et al. 2014, ApJ; Lopez-Sepulcre, Jaber et al. 2015, MNRAS), one accepted article (Jaber et al., A&A) and a final article to be submitted (Jaber et al., A&A)
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De, Leuw Simone. "Manganese and chromium isotopes nebular processes and early solar system chronology /". Diss., Restricted to subscribing institutions, 2009. http://proquest.umi.com/pqdweb?did=1997764951&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Hantoosh, Mohammed, e Mohammed Hantoosh. "Advanced Oxidation Processes of Trace Organics in Water by Solar Photolysis". Thesis, The University of Arizona, 2016. http://hdl.handle.net/10150/620873.
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Wastewater reuse is considered globally as a very important element of sustainable water management. Conventional wastewater treatment methods are not effective for the degradation of toxic trace organic compounds, so advanced treatment processes are sometimes needed when the wastewater effluent is likely to be reused or discharged to a river. The existence of toxic trace organic contaminants in the effluent wastewaters has increased awareness of environmental effects and potential concerns for human health. In this work, the advanced oxidation process (AOP) under solar irradiation was successfully used to decompose p-cresol, which is considered to be a toxic trace organic contaminant, from wastewater effluents. The objective of this thesis was to investigate the effect of the EfOM on the overall degradation of the trace organic matter and bulk organic matter through the formation of reactive oxygen species (ROS) and photoexcited dissolved organic matter intermediates (DOM*) under sunlight irradiation. Solar photolysis experiments were conducted to determine the degradation of p-cresol at different conditions, including varying the secondary effluent WW concentration, the initial concentration of the target compound and light intensity. Results from these experiments were reported and discussed to get the optimal treatment processes.
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Haeussler, Anita. "Solar fuels production by CO2 and H2O splitting via thermochemical processes". Thesis, Perpignan, 2021. https://theses-public.univ-perp.fr/2021PERP0003.pdf.
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Cette étude se focalise sur le développement de procédés de dissociation de H2O et CO2 par voie thermochimique utilisant des oxides métalliques non-stœchiométriques et l’énergie solaire concentrée pour la production de carburants solaires. Les procédés redox se décomposent en deux réactions distinctes : tout d’abord, une réduction thermique à haute température de l’oxyde métallique avec la création de lacunes en oxygène dans la structure cristallographique, entrainant une production d’oxygène ; puis, une réoxydation de l’oxyde métallique par H2O et/ou CO2, conduisant à la production de H2 et/ou CO. La cérine et les pérovskites ont été étudiées comme matériaux réactifs pour les cycles thermochimiques. Pour augmenter l’efficacité des cycles thermochimiques, différents paramètres ont été étudiés, comme la composition chimique et la morphologie de l’oxyde réactif, les conditions opératoires, ainsi que la configuration du réacteur solaire. Dans un premier temps, les activités redox, la cinétique et la thermodynamique de différentes pérovskites ont été étudiées expérimentalement pour les cycles redox. Par la suite, les performances thermochimiques de différents matériaux réactifs sous forme de structures poreuses ou de particules ont été étudiées dans des réacteurs solaires (configuration monolithique ou lit fixe) permettant de réaliser des cycles thermochimiques en deux étapes. Une étude paramétrique détaillée a été effectuée pour déterminer les taux et vitesses de production. La vitesse de production de CO la plus élevée (9.9 mL/min/g) a été obtenue avec des mousses réticulées en cérine. Enfin, un réacteur solaire membranaire a été développé pour produire en isotherme et en continu du CO (ou H2) par dissociation de CO2 (ou H2O) avec une membrane réactive et perméable à l’oxygène. La vitesse de production la plus élevée atteint 0.133 µmol/cm2/s à 1550 °C en utilisant une membrane en cérine avec un revêtement en pérovskiteThis study is focused on the development of thermochemical H2O and CO2 splitting processes using non-stoichiometric metal oxides and concentrated solar energy to produce solar fuels. The redox process is composed of two distinct reactions: first, a thermal reduction at high temperature of the metal oxide with creation of oxygen vacancies in the crystallographic structure, resulting in released oxygen; second, the re-oxidation of the metal oxide by H2O and/or CO2, leading to H2 and/or CO production. Ceria and perovskite materials have been investigated as reactive oxides for thermochemical cycles. To increase the thermochemical process efficiency, different aspects were investigated, such as chemical composition and morphology of the metal oxide, operating parameters, and solar reactor configuration. The redox activities, kinetics and thermodynamics of different perovskite materials were first experimentally investigated for two-step thermochemical cycles. Then, the thermochemical performances of various reactive materials shaped as porous structures or particulate media were investigated in solar reactors (monolithic or packed-bed configurations) able to perform two-step thermochemical cycles. A detailed parametric study was performed to determine fuel production rates and yields. The highest CO production rate (9.9 mL/min/g) was achieved with ceria reticulated foams. Finally, a solar membrane reactor was developed for isothermal and continuous production of CO (or H2) by CO2 (or H2O) splitting with a reactive and oxygen-permeable membrane. The highest CO production rate reached 0.133 µmol/cm2/s at 1550 °C using a perovskite-coated ceria membrane
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Guo, Huairui. "Variation monitoring, diagnosis and control for complex solar cell manufacturing processes". Diss., The University of Arizona, 2004. http://hdl.handle.net/10150/280704.
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Interest in photovoltaic products has expanded dramatically, but wide-scale commercial use remains limited due to the high manufacturing cost and insufficient efficiency of solar products. Therefore, it is critical to develop effective process monitoring, diagnosing, and control methods for quality and productivity improvement. This dissertation is motivated by this timely need to develop effective process control methods for variation reduction in thin film solar cell manufacturing processes. Three fundamental research issues related to process monitoring, diagnosis, and control have been studied accordingly. The major research activities and the corresponding contributions are summarized as follows: (1) Online SPC is integrated with generalized predictive control (GPC) for the first time for effective process monitoring and control. This research emphasizes on the importance of developing supervisory strategies, in which the controller parameters are adaptively changed based on the detection of different process change patterns using SPC techniques. It has been shown that the integration of SPC and GPC provides great potential for the development of effective controllers especially for a complex manufacturing process with a large time varying delay and different process change patterns. (2) A generic hierarchical ANOVA method is developed for systematic variation decomposition and diagnosis in batch manufacturing processes. Different from SPC, which focuses on variation reduction due to assignable causes, this research aims to reduce inherent normal process variation by assessing and diagnosing inherent variance components from production data. A systematic method of how to use a full factor decomposition model to systematically determine an appropriate nested model structure is investigated for the first time in this dissertation. (3) A Multiscale statistical process monitoring method is proposed for the first time to simultaneously detect mean shift and variance change for autocorrelated data. Three wavelet-based monitoring charts are developed to separately detect process variance change, measurement error variance change, and process mean shift simultaneously. Although the solar cell manufacturing process is used as an example in the dissertation, the developed methodologies are generic for process monitoring, diagnosis, and control in process variation reduction, which are expected to be applicable to various other semiconductor and chemical manufacturing processes.
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Tang, Jian. "From Silicon to Germanium Nanowires : growth processes and solar cell structures". Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLX014/document.
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Cette thèse a pour objectif de développer des nouvelles architectures de cellules solaires à base de nanofils produites par un procédé VLS assisté par plasma. La modélisation optique est utilisée pour déterminer le champ et le profil d'absorption dans les cellules solaires. Un courant de 14 mA/cm2 a été obtenu pour des cellules tandem a-Si:H/μc-Si:H. Un modèle électrique a aussi été développé, permettant une compréhension approfondie du transport dans ces dispositifs. En étudiant la croissance de SiNWs étape par étape, une bonne compréhension du processus de croissance a été obtenue, permettant d’expliquer la forte évolution de la densité de nanofils, de leur morphologie et de leur cristallinité. La phase hexagonale de Si a été observée dans les nanofils de silicium de petit diamètre (< 10 nm). Nous avons fait des caractérisations TEM dans la direction [11-20] qui apportent une preuve claire de la phase hexagonale de Si dans les SiNWs. Une fois la croissance de nanofils de silicium optimisée, nous avons abordé la croissance de nanofils de Ge et d’alliages SiGe dans le but de réduire le gap et élargir le domaine spectral de nos cellules. Le contenu en Ge a été varié entre 0 et 100% avec des catalyseurs Sn, In et Cu. Nous avons constaté qu’au-dessus d'une température critique (~350 °C), on peut obtenir des nanofils de Ge cylindriques, longs de plusieurs microns. Des cellules solaires PIN à jonction radiale avec une couche intrinsèque à base d’a-Si:H, de µc-Si:H ou d’-SiGe:H ont été fabriquées. A notre connaissance, c'est la première démonstration d’un tel dispositif à base de nano fils SiGeThis thesis is dedicated to develop new solar cell architectures based on nanowires produced by a plasma-assisted Vapor Liquid Solid process. By optical modeling, detailed field and absorption profiles in the NW solar cells have been obtained and a 14 mA/cm2 matched photocurrent has been achieved for a-Si:H/µc-Si:H tandem solar cells. An electrical model for radial PN junction NW solar cells has also been developed from first principle rules, allowing a good understanding of the carrier transport. By analyzing step by step the SiNWs growth in a PECVD system we could propose a detailed explanation for the strong evolution of the NW density, morphology and crystallinity during growth. The rare hexagonal phase of Si has been observed in the as grown SiNWs with diameters smaller than 10 nm. For the first of time, we have provided TEM characterizations from [11-20] direction to give a clear proof of the hexagonal Si phase in as grown SiNWs. To develop low band bap, high mobility material for multi junction NW solar cells, we added germane to silane during the plasma-assisted VLS growth process. Ge contents from 0 to 100% have been achieved with Sn, In and Cu catalysts. We have found that above a critical temperature (~ 350 °C), micrometer long cylindrical Ge NWs can be obtained. NW based PIN radial junction solar cells having a-Si:H, a-SiGe:H and µc-Si:H as intrinsic absorber layers have been fabricated. For the SiGeNWs based solar cells, a 6% energy conversion efficiency has been achieved with p-i-n configuration. To our knowledge, this is the first demonstration of SiGeNWs based photovoltaic device
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Clemens, A. J. "Pickup ion processes associated with spacecraft thrusters : implications for solar probe plus". Thesis, Queen Mary, University of London, 2016. http://qmro.qmul.ac.uk/xmlui/handle/123456789/18424.
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Chemical thrusters are widely used in spacecraft for attitude control and orbital manoeuvres. They produce a plume of neutral gas which produces ions via photoionisation and charge exchange. Measurements of local plasma properties will be aff ected by perturbations caused by the coupling between the newborn ions and the plasma. A model of neutral expansion has been used in conjunction with a fully three-dimensional hybrid code to study the evolution and ionisation over time of the neutral cloud produced by the ring of a mono-propellant hydrazine thruster as well as the interactions of the resulting ion cloud with the ambient solar wind. A parameter survey was performed for varying angles of injection and injection rates, particle kinetics were also investigated. Results are presented which show that the plasma in the region near to the spacecraft will be perturbed for an extended period of time with the formation of an interaction region around the spacecraft, a moderate amplitude density bow wave bounding the interaction region and evidence of an instability at the forefront of the interaction region which causes clumps of ions to be ejected from the main ion cloud quasi periodically and the ways in which these features are modifi ed by the degree of solar wind mass loading and the relative orientation of the magnetic fi eld to the angle of injection. This may a ffect Solar Probe Plus for a signifi cant duration as data taking and delicate sensory equipment may be required to cease operation until local fluctuations return to a more moderate level. The scale of the fluctuations seen are dependent upon the duration of the thruster ring and the speci fic geometry and therefore e ffects may vary in-situ.
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Layden, Andrew. "Mode Conversion Processes in Magnetized Plasmas". Thesis, The University of Sydney, 2013. http://hdl.handle.net/2123/10437.
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Mode conversion processes in plasmas allow wave energy to transferred between two or more different wave modes, and are often invoked in theories of space and astrophysical phenomena. For instance, electrostatic Langmuir waves which are trapped in the solar wind plasma can be converted to electromagnetic radiation and produce radio bursts, which can propagate through the plasma and thus be observed remotely. In environments where mode conversion has been invoked there is often a significant ambient magnetic field. This modifies the dispersion relations of the wave modes and can result in additional wave modes. However, magnetization effects have been neglected in the analyses of certain mode conversion processes. This thesis presents a number of investigations into mode conversion processes as they occur in magnetized plasmas, focusing on the magnetization of the Langmuir mode.
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Bras, Patrice. "Sputtering-based processes for thin film chalcogenide solar cells on steel substrates". Doctoral thesis, Uppsala universitet, Fasta tillståndets elektronik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-329778.
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Thin film chalcogenide solar cells are promising photovoltaic technologies. Cu(In,Ga)Se2 (CIGS)-based devices are already produced at industrial scale and record laboratory efficiency surpasses 22 %. Cu2ZnSn(S,Se)4 (CZTS) is an alternative material that is based on earth-abundant elements. CZTS device efficiency above 12 % has been obtained, indicating a high potential for improvement. In this thesis, in-line vacuum, sputtering-based processes for the fabrication of complete thin film chalcogenide solar cells on stainless steel substrates are studied. CIGS absorbers are deposited in a one-step high-temperature process using compound targets. CZTS precursors are first deposited by room temperature sputtering and absorbers are then formed by high temperature crystallization in a controlled atmosphere. In both cases, strategies for absorber layer improvement are identified and implemented. The impact of CZTS annealing temperature is studied and it is observed that the absorber grain size increases with annealing temperature up to 550 °C. While performance also improves from 420 to 510 °C, a drop in all solar cell parameters is observed for higher temperature. This loss is caused by blisters forming in the absorber during annealing. Blister formation is found to originate from gas entrapment during precursor sputtering. Increase in substrate temperature or sputtering pressure leads to drastic reduction of gas entrapment and hence alleviate blister formation resulting in improved solar cell parameters, including efficiency. An investigation of bandgap grading in industrial CIGS devices is conducted through one-dimensional simulations and experimental verification. It is found that a single gradient in the conduction band edge extending throughout the absorber combined with a steeper back-grading leads to improved solar cell performance, mainly due to charge carrier collection enhancement. The uniformity of both CIGS and CZTS 6-inch solar cells is assessed. For CZTS, the device uniformity is mainly limited by the in-line annealing process. Uneven heat and gas distribution resulting from natural convection phenomenon leads to significant lateral variation in material properties and device performance. CIGS solar cell uniformity is studied through laterally-resolved material and device characterization combined with SPICE network modeling. The absorber material is found to be laterally homogeneous. Moderate variations observed at the device level are discussed in the context of large area sample characterization. Power conversion efficiency values above 15 % for 225 cm2 CIGS cells and up to 5.1 % for 1 cm2 CZTS solar cells are obtained.
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Henning, Annette. "Ambiguous Artefacts : Solar Collectors in Swedish Contexts. On Processes of Cultural Modification". Doctoral thesis, Högskolan Dalarna, Miljöteknik, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:du-950.
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This is a book about solar collectors and the place of these artefacts in a political energy debate that has aroused strong feelings in Sweden during the last twenty-five years. It is a book about the hopes for a less polluted earth, which solar collectors have come to symbolise, and a book about the ways in which problems in utilising solar energy are culturally perceived. One main aims of this study has been to find out more about the conflicting perceptions of solar collectors as 'saviours of the world' and simultaneously as uninteresting or less credible artefacts that 'may come in the future'. Another main purpose of the study has been to describe and explain those cultural processes of modification that are taking place around solar collectors in active attempts to integrate these into established cultural structures.
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Theis, Karen Julia. "Iron isotope fractionation of planetary bodies during early solar system formation processes". Thesis, University of Manchester, 2008. http://www.manchester.ac.uk/escholar/uk-ac-man-scw:163898.
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The aims of this research programme were twofold: to analyse the iron isotope compositions of metal grains from ordinary chondrite meteorites over a range of class and petrographic type to investigate redox reactions and thermal metamorphism during primitive planetesimal formation; and to analyse the iron isotope composition of secondary carbonate minerals in Martian meteorite ALH84001 to determine the formation temperature and thus constrain near surface conditions on early Mars. To analyse the iron isotope compositions of these materials it was necessary to develop a methodology using a Nu Plasma multi collector inductively coupled plasma mass spectrometer and a new technique for analysing natural iron-bearing samples without first purifying them by anion exchange chromatography. The purification process can cause fractionation within the sample which may mask small natural fractionation variations. The new methodology developed here yielded reproducible iron isotope ratios to within o.osroo (20) ensuring that small isotopic variations of (i56Fe -0.06roo to 0.3sroo were resolved during the analysis of the ordinary chondrite metal grains. The method for analysing samples containing matrix elements was successful and achieved an accuracy and precision comparable to pure analyte solutions for the analysis of the Martian carbonates. The analysis of the metal grains revealed a correlation between their iron isotope compositions and the redox and thermal metamorphism that these materials have experienced. The results indicate that the degree of iron isotope fractionation can be related to thermal metamorphism temperatures, except for metal grains from type 3 chondrites. This was interpreted as resulting from the type 3 chondrites not getting hot enough during thermal metamorphism to overprint the original igneous isotopic signatures. The a-rich carbonates in ALH84001 were petrographically characterised to place them within the known carbonate assemblage sequence which implied that the zoned carbonate deposition occurred during multiple phases. The zoned carbonates were then analysed for iron isotope composition and an isotopic fractionation variation for (i56Fe of -0.6%0 was determined relative to bulk Martian silicates. This indicated a formation temperature of approximately ±800( (20) and implied that liquid water was stable on or near the surface during this time.
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Kolodziej, Charles. "Laser Spectroscopic Studies of Ultrafast Charge Transfer Processes in Solar Cell Materials". Case Western Reserve University School of Graduate Studies / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=case1586371698913592.
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Nissfolk, Jarl. "Charge Transport Processes in Mesoporous Photoelectrochemical Systems". Doctoral thesis, KTH, Organisk kemi, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9849.
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During the last decade, the dye sensitised solar cell (DSC) has attracted much attention. The technology has a potential to act as a new generation of photovoltaic device, it has also increased our knowledge within the field of photoelectrochemistry. The materials used in the DSC have been used in other technologies, such as electrochromic displays. This thesis examines how such systems can be analysed to understand their properties from their components. Both of the considered device technologies consist of a thin mesoporous semiconductor film immersed in an electrolyte. The study starts by investigating some of the fundamental properties of the mesoporous semiconductor and its interface with the electrolyte. This gives rise to the charge-voltage relationship for the devices, which is related to the chemical capacitance and electronic energy levels for the materials. In particular,special attention is given to the DSC and the properties of the charge carriers in the semiconductor. For the DSC, several techniques have been developed in order to understand the processes of transport and recombination for the charge carriers in the semiconductor film, which are vitally important for performance. In this thesis, particular focus is given to light modulation techniques and electrical analysis with impedance spectroscopy. The transportproperties show for both techniques a nonlinear behaviour, which is explained with the trapping model. The DSC solar cell is analysed in order to interpret the transport measurements for film thickness optimisation. DSC cells with new semiconductor materials, such as ZnO, were analysed with impedance measurements to provide new insights into the optimisation of the performance of the photoelectrochemical solar cell technology.QC 20100804
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Al-Achkar, Mohamed. "Efficiency enhancement and degradation processes in Cuâ†xS/CdS thin film solar cells". Thesis, University of Hull, 1990. http://hydra.hull.ac.uk/resources/hull:3703.
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An investigation has been made into the structure and properties of polycrystalline CuxS-CdS solar cells in order to develop an improved understanding of some of the processes which lead to unsatisfactory reproducibility and long term stability of the characteristics of these devices. The cells studied during this project were fabricated using vacuum evaporation for production of the CdS base layer and the well known chemical exchange process in a CuCl solution for formation of the CuxS layer. In view of the non-uniform thickness of the CuxS layer and non-planar structure of the Cu, S-CdS interface, it was found to be necessary to employ a variety of different characterisation techniques to monitor changes in the structure and properties of the devices. These techniques included I/V, C-V, spectral response and sheet resistance measurements, electrochemical analysis, cathodoluminescence spectroscopy and Rutherford backscattering. Detailed consideration was given to the influence of the conditions of formation on the properties of each cell component, in order to establish procedures necessary for the production of reproducible structures. particular attention was paid to the rate of growth of the CuxS layer and a theoretical analysis was developed to account for the time dependence of the growth in mean thickness of the CuxS layer in terms of the contributions associated with growth at the surface of the CdS layer and in the CdS grain boundary regions. The grain boundary contribution was found to be very sensitive to the CdS grain structure and to the previous treatment given to the CdS layer. Pre-annealing in air at 2000C enhanced the grain boundary penetration while the effect of ion implantation (with either Cu or Zn ions) was found to depend on the initial structure and the implantation conditions, but substantial improvements in the photovoltaic conversion efficiency were shown to be possible as a result of such treatment.The rate of degradation of cells exposed to air was also found to be dependent on the previous history of the cell. An increased concentration of Cd in the CuxS film (due to diffusion from the CdS layer) appeared to reduce the rate of qegradation while use of the standard stabilizing treatment (deposition of Cu overlayer followed by annealing in air) was shown to reduce interfacial diffusion as well as protecting the front surface of the CuxS layer against oxidation.
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Kolotkov, Dmitrii. "Nonlinear and multi-modal oscillatory processes in active regions of the solar atmosphere". Thesis, University of Warwick, 2017. http://wrap.warwick.ac.uk/93215/.
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For longer than a century, analysis of a quasi-periodic variability of the Sun on various time scales has been attracting great interest among the research community. These signals are continuously detected throughout the whole electromagnetic spectrum, and often have non-stationary oscillation periods and irregular profile shapes. The physical mechanisms responsible for such variations are usually hidden, and their revealing always require an advanced combination of powerful spectral techniques and strong theoretical foundations. This thesis considers oscillatory phenomena occurring in the solar atmosphere from these two perspectives. For the spectral analysis of solar periodicities the self-adaptive Hilbert–Huang transform (HHT) method is employed. With the statistics of coloured noises incorporated, it allowed for the detection of a long-period oscillation of a small-scale photospheric magnetic structure, whose period grows from 80 to 230 min and positively correlates with the amplitude. A multi-modal nature of the solar flare quasiperiodic pulsations was also revealed with HHT. The detected intrinsic modes have mean periods of 15, 45, and 100 s, and can be interpreted as the kink and sausage magnetohydrodynamic oscillations of a flaring loop. Analysis of much longer solar periodicities associated with the magnetic activity cycles 22, 23, and 24 was also successfully performed with HHT, revealing a broad range of intrinsic modes with periods from about a month to several years (including the 11 yr cycle). From the theoretical point of view, the one-dimensional equilibrium and dynamical models of current sheets in the corona have been developed. The equilibrium model provides an inhomogeneous distribution of macroscopic plasma parameters across the current sheet, as found for realistic physical conditions. The dynamical model describes nonlinear oscillations of the current sheet formed by the coalescence of two magnetic flux ropes. The oscillation period is found to be about the ion plasma period or longer, and is prescribed by the current sheet thickness, the plasma parameter β, and the oscillation amplitude. Analytical modelling of finite amplitude transverse oscillations in quiescent prominences situated in a magnetic field dip, is also performed in the thesis. The model is based on the line-current concept and accounts for the interaction of the prominence current with the electrically conductive photosphere. In the linear regime, the horizontal and vertical motions are considered independently, and the mechanical stability of the system is analysed. The oscillation periods are determined by the prominence current, its mass and height above the photosphere, and the properties of the magnetic dip. In the case of finite amplitudes, the horizontal and vertical modes were found to be nonlinearly coupled with each other, and a metastable equilibrium state of the prominence was revealed. The periods of nonlinear oscillations are shown to depend upon the oscillation amplitude.
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Bashir, Muktar. "A novel approach for integrating concentrated solar energy with biomass thermochemical conversion processes". Thesis, Aston University, 2017. http://publications.aston.ac.uk/30868/.
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Concentrated solar energy provides thermal energy that can be utilised for thermochemical conversion of biomass to produce liquid fuel and gases. This creates an efficient and a carbon-free process. The fast pyrolysis of biomass is an endothermic thermal process that occurs within 400-550oC at fast heating rates of >300 oC/second in the absence of oxygen. This temperature is within the range produced in a parabolic trough arrangement. The process of biomass gasification is the conversion of biomass fuels to non-condensable gases usually for chemical feedstock or as fuel using a fluidising medium. Solar intermittence is a major issue; this can be resolved by proposing a continuous process from concentrated solar energy to fuels or chemical feedstock. Computational fluid dynamics has proven to be a tool for design and optimisation of reactors. The Eulerian-Eulerian multiphase model using ANSYS Fluent has shown to be cost-effective at describing the characteristics of complex processes. The project entails using parabolic trough for fast pyrolysis of biomass; it is integrated with a gasification process with utilities produced entirely from solar energy. The scope of the project are: (i) A Computational fluid dynamic (CFD) model analysis of the novel reactor is to be developed to model biomass pyrolysis (ii) Investigate the potentials of integrating the proposed solar reactor with a conventional circulating fluidised bed (CFB) gasifier to create a highly efficient and sustainable closed loop thermo-solar process (iii) Validate the circulating fluidised bed model with an experimental scale Circulating fluidised bed (CFB) gasifier at Aston University’s European Bioenergy Research Institute. The report studied the use of CFD modelling to investigate fast pyrolysis of switch grass biomass using a solar parabolic trough receiver/reactor equipped with a novel gas-separation system. The separator controls the effect of tar-cracking reactions and achieves high separation efficiency compared to other gas-solid separation methods. The study assumes an average heat flux concentrated along the receiver/reactor. Pyrolysis reaction was represented as a single global first order Arrhenius type reaction with volatiles separated into condensable (bio-oil) and non-condensable products. The drying of moisture of the switch grass was represented as a mass transfer process. The separation efficiency achieved by the conical deflector was about 99%. The proposed reactor at the considered operating conditions can achieve overall energy efficiency of 42%; the product yield consist of 51.5% bio-oil, 43.7% char and 4.8% non-condensable gases. The average reactor temperature, gas residence time, and maximum devolatilisation efficiency were 450 °C, 1.5 s, and 60% respectively. There was good agreement in comparison with experimental findings from literature. A sensitivity analysis was conducted to study the effect of heat flux conditions, heat transfer, sweeping gas temperature, and particle size. The heat flux distribution showed that non-homogeneous provides a greater heating rate and temperature compared to the homogeneous flux. Radiation negligibly affects the final product composition; the radiation heats the biomass mainly rather than cause devolatilisation. The larger the biomass diameter the more bio-oil is produced, when a uniform particle temperature is assumed. An experimental study was conducted for the validation of the hydrodynamic model of a circulating fluidised bed. The experiment measured the pressure profiles and the solid recirculation rate. The experiment result showed that particle size has a negative correlation to the ease of fluidisation. High fluidising gas flowrate has a positive impact on the fluidising regime and pressure in the riser. The following parameters were compared with experimental results: grid size, turbulence model, drag laws, wall treatment, and wall shear properties (specularity coefficient and restitution coefficient). The results proved the optimum hydrodynamic model through comparison of pressure profiles of the model with experimental results. The gasification of char in a circulating fluidised was studied using the optimum hydrodynamic model validated from experiment. The model considered the effect of turbulence on the species evolution and tar reforming with char. Over the range of operating conditions, the results looked into the hydrodynamics and product yield of the gasifier. The product yields obtained for the base case was CO (12%), CO2 (19%), H2 (6%), CH4 (0.7%), and N2 (63%). The results proved that for smaller particles the evolution of species are dominated by kinetics. The catalytic effect of char showed improvement in tar yield and CGE to 15.12g/Nm3 and 67.74%. The product yields showed improvement with the compositions of CO2 and H2 due to reforming reactions. The yields and efficiency were in qualitative agreement with results from literature. The proposed models described will provide details on the procedures for future design of integrated solar biomass thermochemical conversion systems.
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Schmich, Evelyn Karin. "High-temperature CVD processes for crystalline silicon thin-film and wafer solar cells". München Verl. Dr. Hut, 2008. http://d-nb.info/992162874/04.
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Deng, Zhuo, e 鄧卓. "Luminescence and transport processes of charge carriers in the GaxIn₁-xP/GaAs double-junction tandem solar cells". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/211134.
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Semiconductor multijunction solar cell is a cutting-edge photovoltaic technology aimed at developing a frontier solution to the clean energy demand and environmental problem. Due to the efficient photoabsorption and energy conversion in the visible and near-infrared spectral ranges of the solar spectrum, the multijunction solar cell structures have shown an unprecedented application potential by demonstrating a solar conversion efficiency of over 44 %. Among various multijunction solar cell structural designs, the GaxIn1-xP/GaAs double-junction tandem structure is considered as the most fundamental building block for developing the industry-standard triple- and even more junction photovoltaic cells with super high efficiency. Therefore, obtaining a better and more in-depth understanding of physical properties of the GaxIn1-xP/GaAs double-junction tandem device structure, especially some fundamental optoelectronic processes in the individual structural layer, including photoexcitation, transport and the mid-way recombination of charge carriers, is crucial for further improving the energy conversion efficiency. In this thesis, the mid-way radiative recombination, diffusion transport, localization mechanism, and photocurrent spectra of charge carriers in the GaxIn1-xP/GaAs double-junction tandem solar cells grown on GaAs substrates with different misorientation angles were investigated in detail.
Our main findings are summarized as below. Efficient radiative recombination of carriers in the GaxIn1-xP/GaAs double-junction tandem solar cell samples was demonstrated by using electroluminescence (EL) and photoluminescence (PL) techniques. The radiative recombination intensity was shown to be dependent on the intrinsic material-related parameters such as the doping concentration, growth thickness and the substrate misorientation angle both experimentally and theoretically. The radiative recombination was thus revealed to be an important loss channel of carriers in the GaxIn1-xP/GaAs double-junction tandem solar cells.
Super strong transverse diffusion of minority carriers in the top GaxIn1-xP subcell was found by the micro-EL image surveying. Theoretical simulation on the experimental data shows that the minority carrier diffusion length is as long as ~93 μm at a forward bias of 2.75 V, which is ~30 times longer than that of unbiased GaxIn1-xP epilayer. Origin of this super transverse diffusion was argued, and its influence on device performance was also discussed.
Significant correlations of carrier localization and luminescence behaviors with the substrate misorientation angle in the top GaxIn1-xP subcells were unveiled by excitation intensity- and temperature-dependent PL. The large difference in potential energy profile of GaxIn1-xP layers, caused by the different degrees of atomic ordering, was argued to interpret the observed PL distinctions.
Vertical transport and photoresponse mechanisms of charge carriers in the GaxIn1-xP/GaAs double-junction tandem solar cells were studied by temperature- and reverse bias-dependent photocurrent (PC) spectroscopy. Both the temperature and reverse bias were shown to have significant impact on the device photoresponse, in particular on the photoresponse due to the absorption of photons with energy above the bandgap of GaAs and GaxIn1-xP, namely the supra-bandgap photoresponse. A model was proposed to simulate the observed temperature- and reverse-bias dependence of the supra-bandgap photoresponse.published_or_final_version
Physics
Doctoral
Doctor of Philosophy
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Hudson, Stephen R. "Solar radiation processes on the East Antarctic Plateau : interaction of clouds, snow, and atmospheric gases /". Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/10066.
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Potter, Stephen Edward. "Modelling of three-dimensional transient conjugate convection-conduction-radiation heat transfer processes and turbulence in building spaces". Thesis, Northumbria University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245440.
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Neuschitzer, Markus. "Development of Cu2ZnSnSe4 Based Thin Film Solar Cells by PVD and Chemical Based Processes". Doctoral thesis, Universitat de Barcelona, 2016. http://hdl.handle.net/10803/400489.
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Nowadays mono- and multicrystalline silicon have the highest market share of all PV technologies but thin film solar cells based on CdTe or Cu(In,Ga)Se2 (CIGS) absorbers recently show promising high power conversion efficiency values and due to their short energy payback time, minimal use of high purity material and low cost, they attract more and more attention. However, one concern of thin film PV based on CdTe or CIGS is the use of scare elements like tellurium or indium and gallium which could become a bottleneck if the technology wants to scale up to the terawatt level. Therefore, there is a high interest to replace these scare elements by more abundant ones and find suitable earth abundant photovoltaic absorbers. Cu2ZnSnSe4 (CZTSe) or Cu2ZnSnS4 (CZTS) and its sulphur-selenide solid solution are promising candidates to replace CIGS as absorber material due to its composition of more earth abundant elements. In literature CZTSe and CZTS are referred to as kesterite due to its crystal structure. However, there is still a large gap between power conversion efficiencies of solar cells based on kesterite absorber material and more established thin film solar cells, thus intensive research is still necessary to close this gap. The main goal of this thesis was to develop and optimize heterostructure solar cells based on Cu2ZnSnSe4 absorbers, by cost effective physical vapour deposition (PVD) and chemical based processes. Special focus is put on an improved understanding of the influence of the surface properties of kesterite absorbers on device performance and furthermore to optimize the front interface, i.e. buffer layer as well as the kesterite absorber layer itself. A detailed study investigating the influence of the surface chemistry on device performance is presented. After a chemical etching to remove unwanted ZnSe secondary phases formed during CZTSe absorber synthesis a low temperature post deposition annealing at 200ºC of the full solar cell is necessary to improve device efficiencies from below 3% to over 8%. X-ray photoelectron spectroscopy (XPS) surface analysis showed that this post deposition annealing promotes the diffusion of Zn towards the surface and Cu towards the bulk resulting in a Zn enriched and Cu depleted surface region, which is crucial for high device performance. Additionally experimental surface treatments confirm the necessity of a Cu-poor and Zn-rich surface and the reason for this beneficial surface composition are discussed in detail. Furthermore, the CdS buffer layer which is typically used in kesterite based heterostructures solar cells was optimized and allowed improvements in device performance of 1% absolute. This optimization was further extended to Cd-free ZnS(O,OH) buffer layer. Efficiencies close to that of CdS reference solar cells could be achieved using optimized ZnS(O,OH) buffer layer. Additionally to the front interface optimization, a Ge assisted crystallization process for nanocrystalline CZTSe precursors was developed which largely increase grain growth and boost open circuit voltages (Voc) to promising high values due to the elimination of deep defects. Since the low Voc values is identified of one of the main bottlenecks of kesterite technology, the improvements achieved are highly promising and give important insight for further possible optimizations.Los compuestos Cu2ZnSnSe4 (CZTSe), Cu2ZnSnS4 (CZTS) y Cu2ZnSnSexS4-x (CZTSSe) también conocidos como kesteritas debido a su estructura, presentan propiedades prometedoras para sustituir a la tecnología de células solares de capa fina basadas en Cu(In,Ga)Se2, evitando el problema potencial que podría generar el uso de indio y galio. A día de hoy, las eficiencias obtenidas en dispositivos de CIGS, son bastante mayores que las reportadas para dispositivos de kesteritas, debido entre otras razones a la diferencia en la madurez de dicha tecnología. Por lo tanto, es necesario un estudio más profundo de los materiales y dispositivos basados en kesteritas, enfocado a aumentar los valores de eficiencia de los dispositivos. El objetivo principal de esta Tesis Doctoral es el desarrollo y optimización de células solares con capas absorbentes basadas en el compuesto CZTSe por métodos de bajo coste incluyendo procesos de deposición física en fase vapor, así como también por procesos químicos. Se ha prestado especial interés en aumentar el conocimiento sobre la influencia de las propiedades de la superficie de la capa absorbente en el funcionamiento de las células solares. Estos estudios incluyen la optimización de la capa de kesterita, y también de su interfaz con la capa “buffer” o semiconductor tipo n en la heterounión. Se incluye un estudio detallado de la influencia de las propiedades químicas de la superficie del absorbente en la eficiencia de los dispositivos. Además, se presentan los estudios de optimización de la capa buffer basada en CdS y de capas buffer libres de Cd, usando como alternativa ZnS(O,OH), donde se obtuvieron eficiencias comparables con las de los dispositivos de referencia fabricados con CdS. Finalmente, se presenta un estudio de recristalización asistida por una capa nanométrica de Ge depositada en los precursores nano cristalinos. Se demuestra que este proceso induce un aumento significativo del crecimiento de los granos del absorbedor, reduciendo la presencia de defectos profundos eléctricamente activos que resultan perjudiciales para las propiedades de los dispositivos fotovoltaicos. Las mejoras presentadas en este estudio son altamente prometedoras y conducen hacia nuevas rutas de optimización en la fabricación de estos dispositivos.
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Boghossian, Ardemis A. (Ardemis Anoush). "An engineering analysis of natural and biomimetic self-repair processes for solar energy harvesting". Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/76478.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 191-201).
Plants have evolved highly sophisticated mechanisms of self-repair to regenerate proteins that become photo-damaged over time. Key to this self-repair process is the reversible self-assembly of protein complexes, which is characterized by the molecular recognition of parts, kinetic trapping of meta-stable thermodynamic states, and chemical signaling to switch between states. In this thesis, we mimic such regenerative mechanisms in an effort to develop biological light-harvesting devices with prolonged lifetimes. We demonstrate the first synthetic photoelectrochemical cell capable of mimicking key aspects of the self-repair process. Surfactant addition and removal was used to signal between the disassembly and re-assembly of a photoactive complex demonstrating photo-conversion efficiencies of 40%. These dynamic complexes consist of lipid bilayer disks housing photoactive reaction centers (RCs) that align along the length of a single-walled carbon nanotube (SWNT). Application of a regeneration cycle that reversibly signals between the assembled and disassembled states extends the lifetime of the photoelectrochemical cell indefinitely and increases cell efficiency by over 300% over 168 hours. We modeled the kinetic and thermodynamic forces that drive the reversible self-assembly, and we fit this model to spectrofluorimetric measurements that monitor complex formation. The bestfit rate constants for lipid bilayer and bilayer-nanotube complex formation are 79 mM-Is'Iand 5.4x 10 mM-1 s- 1, respectively. We find that these reactions do not occur under diffusioncontrolled conditions, and the phase diagram predicts a locally optimal surfactant removal rate of 8 x 10-4 s-1. This model was subsequently fit to cyclic complex assembly and disassembly measurements, demonstrating that the forces modeled in this study may form the basis for synthetic and natural photoactive complexes capable of dynamic component repair. In an effort to extend our scope to study natural regeneration mechanisms, we established a platform for quantifying reactive oxygen species (ROS) generation in isolated chloroplasts capable of autonomous regeneration. ROS generation from illuminated chloroplasts from S. oleracea was examined in the presence of dextran-wrapped nanoceria (dNC), cerium ions (Ce3 ), fullerenol, and DNA-wrapped SWNTs. ROS concentrations were evaluated using the oxidative dyes, 2',7'- dichlorodihydrofluorescein diacetate (H2DCF-DA) and 2,3-bis(2-methoxy-4-nitro-5- sulfophenyl)-2H-tetrazolium-5-carboxanilide sodium salt (XTT). Chloroplast photoactivity was monitored throughout the illumination period using chloroplast fluorescence and the artificial, photosynthetic electron accepting dye, dichloroindophenol (DCPIP). The results of this study indicate that dNC offers a promising mechanism for effective ROS scavenging whilst preserving chloroplast photoactivity at concentrations below 5 [tM. We have also established several platforms for studying the glucose production of isolated chloroplasts for biofuel cell applications. We developed an algorithm to quantify single-molecule efflux measurements from individual, photoactive chloroplasts. Near-infrared fluorescing SWNTs have been used in previous studies to report single-molecule binding events via stochastic fluctuations in fluorescence. In this thesis, we develop and compare several algorithms for extracting concentration-dependent rates from the stochastic fluctuations. Overall, the birthand- death model most accurately predicts the rate constants, whereas the moment analysis is more accurate at large forward rates (>10-3 s-1). Glucose efflux from chloroplasts was characterized using a glucose oxidase assay, high-pressure liquid chromatography (HPLC), and a biofuel cell. Calculated export rates of 1.9 and 6 tmol/(mg chlorophyll hr) were measured using the HPLC and fuel cell, respectively. Maximum power densities of 110 pW/cm 2 were achieved with alginate encapsulated chloroplasts. In the presence of regenerative materials, such as dNC, this biofuel cell setup provides a promising platform for demonstrating a biological lightharvesting construct capable of autonomous regeneration
by Ardemis A. Boghossian.
Ph.D.
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Barulina, Elena. "Study of the photostability of organic solar cells : impact of materials and encapsulation processes". Electronic Thesis or Diss., Aix-Marseille, 2020. http://theses.univ-amu.fr.lama.univ-amu.fr/201209_BARULINA_247fcnnrd470uh345hs973z_TH%20(1).pdf.
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Malgré une forte progression des rendements de conversion électrique des cellules solaires organiques, leur stabilité à long terme est un facteur clé pour leur viabilité commerciale et doit donc être examinée en détail. L'objectif était ici d’étudier la durée de vie des cellules solaires organiques en variant les matériaux actifs du mélange D:A, l'architecture des cellules, les couches interfaciales, les traitements appliqués et le processus d'encapsulation. Quel que soit ces paramètres, une grande stabilité a pu être obtenue pour des dispositifs à base de PC71BM sous LED. Par contre sous AM1.5, un post-recuit améliore considérablement la stabilité des dispositifs, mais le choix de la structure de la cellule reste le paramètre clé où seules les cellules en structure normale ont montré une grande stabilité dans le temps. Ces couches ont été étudiées par spectroscopie d'absorption, AFM, XRD et TEM analytique. Les dispositifs à base de PC71BM peuvent ainsi servir de référence dans l’étude de la stabilité des mélanges à base de NFAs (PBDB-T:ITIC et PBDB-T-2F:ITIC-4F). Outre l’éclairage (LED ou AM1.5) et les divers paramètres, les cellules solaires à base de NFA sont instables. Sous LED, les cellules solaires à base d’ITIC-4F présentent une meilleure stabilité que celles à base d'ITIC mais cette dégradation dépend aussi très fortement de la nature chimique de la couche d’extraction d’électron. Des procédés d'encapsulation flexibles sur les modules imprimés par jet d'encre de la société Dracula Technologies ont été évalués. Ces modules ont démontré des propriétés relativement stables après 1000 heures d'éclairage continu par une lampe au xénon non filtrée en UVDespite a strong increase in the electrical conversion efficiencies of organic solar cells, their long-term stability is a key factor for their commercial viability and therefore needs to be examined in detail. The objective here was to study the lifetime of organic solar cells by varying the active materials in the D:A mixture, the cell architecture, the interfacial layers, the treatments applied and the encapsulation process. Regardless of these parameters, a high stability could be obtained for PC71BM-based devices under LED. On the other hand, under AM1.5, a post-annealing process considerably improves the stability of the devices, but the choice of the cell structure remains the key parameter where only cells with normal structure showed a high stability over time. These layers were studied by absorption spectroscopy, AFM, XRD and analytical TEM. PC71BM-based devices can thus serve as a reference in the study of the stability of mixtures based on NFAs (PBDB-T:ITIC and PBDB-T-2F:ITIC-4F). Regardless of the illumination (LED or AM1.5) and the various parameters, NFA-based solar cells are unstable. Under LEDs, ITIC-4F-based solar cells have a better stability than ITIC-based solar cells, but this degradation also depends very strongly on the chemical nature of the electron extraction layer. Flexible encapsulation processes on ink-jet-printed modules from Dracula Technologies have been evaluated. These modules demonstrated relatively stable properties after 1000 hours of continuous illumination by a non-UV-filtered xenon lamp
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Merino, Jose Carlos Alvarez, e Kazuo Hatakeyama. "Technology surveillance of the solar refrigeration by absorption/adsorption". Institute of Electrical and Electronics Engineers Inc, 2016. http://hdl.handle.net/10757/622310.
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PICMET 2016 - Portland International Conference on Management of Engineering and Technology: Technology Management For Social Innovation, Proceedings4 January 2017, Article number 7806767, Pages 1976-19822016 Portland International Conference on Management of Engineering and Technology, PICMET 2016; Honolulu; United States; 4 September 2016 through 8 September 2016; Category numberCFP16766-ART;
Code 125891In order to establish networks of cooperation looking for not to duplicate research and even to make use of existing research in a remote form, it is necessary to identify and classify (around the world) the researchers and laboratories, that are researching in the topic of solar refrigeration by absorption/adsorption. The methodology consists in: i) the technology's classification, ii) technological trajectory Identification, iii) a thematic bibliographic review, and iv) patent's analysis. In this way, with the previous determination of keywords, will be identified main authors and their respective institutions. With the same keywords, are determined the licensed patents (in certain span of time). In addition, the analysis of publications, patents, and commercial products give us an opportunity to establish comparisons between prototypes and tests (in several conditions). The larger results implicate the use of actor's network and the remote access to the data and tests, for a collaborative research, overcoming the lack of laboratory resource and accelerating the knowledge acquisition
Revisión por pares
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Vocks, Christian [Verfasser], e Klaus G. [Akademischer Betreuer] Strassmeier. "Electron kinetic processes in the solar corona and wind / Christian Vocks. Betreuer: Klaus G. Strassmeier". Potsdam : Universitätsbibliothek der Universität Potsdam, 2013. http://d-nb.info/1035307405/34.
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Yang, Wenxing. "Exploring Electronic Processes at the Mesoporous TiO2/Dye/Electrolyte Interface". Doctoral thesis, Uppsala universitet, Fysikalisk kemi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-310191.
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Dye sensitized solar cells (DSSCs) are an attractive way to convert light into electricity. Its development requires a detailed understanding and kinetic optimization of various electronic processes, especially those occurring at the mesoporous TiO2/dye/electrolyte interface. This dissertation work is focused on the exploration of the various electronic processes at the sensitized-electrode/electrolyte interface by using various electrochemical and photochemical methods. Firstly, an alternative redox couple—TEMPO/TEMPO·+ with a relatively high positive redox potential—is explored, aiming to reduce the energy loss during the dye regeneration process. Despite the fast dye regeneration, the charge recombination between the electrons in the conduction band of mesoporous TiO2 and the oxidized redox species is found to be the limiting factor of the device. Further, a more efficient tandem-electrolyte system is developed, leading to DSSCs with the power conversion efficiency of 10.5 % and 11.7 % at 1 sun and 0.5-sun illumination, respectively. An electron-transfer cascade process during dye regeneration by the redox mediators is discovered to be beneficial. Further stability studies on the device suggest the crucial role of TiO2/dye/electrolyte interfaces in the long-term stability of cobalt bipyridyl electrolyte-based DSSCs. On the fundamental level, the local electric field and Stark effects at the TiO2/dye/electrolyte interface are investigated in various aspects—including the charge compensation mechanism, the factors affecting the electric field strength, as well as its impact on charge transfer kinetics. These results give further insights about the TiO2/dye/electrolyte interface, and contribute to the further development and understanding of DSSCs.
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Takasao, Shinsuke. "Fundamental Magnetohydrodynamic Processes of Solar Flares: Formation of Flare-productive Regions and Evolution of Flare Loops". 京都大学 (Kyoto University), 2016. http://hdl.handle.net/2433/215316.
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Jenkins, Judith Lynn. "Spectroscopic and Spectroelectrochemical Characterization of Fundamental Interfacial Charge Transfer Processes Relevant to Efficient Solar Energy Conversion". Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/255173.
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Solar energy conversion is accomplished by multilayered devices consisting of various conducting and semiconducting materials. Because the layers are only 10s - 100s of nm thick, device behavior is governed primarily by interfacial molecular dynamics that often differ from the bulk behavior of these materials. The thermodynamics and kinetics of the interfacial interactions are particularly interesting, as interfacial electron transfer strongly influence the efficiency of photovoltaics and devices used in solar hydrogen production. This work focuses specifically on interfacial charge transfer processes occurring at three interfaces relevant to thin film organic/inorganic solar energy conversion devices. i) A potential-step polymer electrochemical deposition and doping procedure was developed and used to create poly(3-hexylthiophene) (e-P3HT) interlayer films for organic photovoltaics. Photoelectron spectroscopies suggest that an interface dipole forms spontaneously at the polymer donor/fullerene acceptor interface through partial interfacial charge transfer prior to photoexcitation; this doping-dependent interfacial dipole was correlated to the electrical properties of these critical heterojunctions. ii) Potential-modulated fluorescence spectroscopy (PMF) was developed and used examine the kinetics of the reversible oxidation of the (e-P3HT) films in attempt to elucidate the ITO/e-P3HT charge transfer rates. However, the optical switching increased linearly as the polymer film decreased, indicating that the molecular-level process probed by PMF was rate-limited by counter-ion movement into and out of the polymer film. iii) Potential-modulated attenuated total reflectance spectroscopy (PM-ATR) was used to examine the reversible reduction of CdSe semiconductor nanocrystals tethered to indium tin oxide electrodes as well as the surface-coverage dependent bleaching of these nanocrystals. A new equivalent circuit model describing the CdSe/ITO electrode is proposed, and a PM-ATR simulation program was used to quantify Faradiac resistances to interfacial charge transfer that trend with the magnitude of overpotential. The insights gained through these experiments add to a growing understanding of the fundamental, molecular-level competition between photoinduced charge generation and parasitic charge recombination at these critical interfaces.
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Cavallari, Marco Roberto. "Desenvolvimento de uma metodologia de fabricação de transistores de filmes finos orgânicos". Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/3/3140/tde-03112010-120818/.
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Neste trabalho, é apresentada uma metodologia de fabricação de transistores de filmes finos orgânicos. Foram fabricadas células solares de heterojunção de poli(3- hexiltiofeno) (P3HT) e [6,6]-fenil-C61-butirato de metila (PCBM) por apresentarem máxima conversão de potência (PCE) de cerca 5 %. Partindo de rendimentos de 10-6 até atingir 1,7 %, são mostradas as dificuldades no processamento de filmes orgânicos e na caracterização destes dispositivos. Destacam-se dentre outros, a importância da geometria dos eletrodos, da preparação da solução de blendas orgânicas e dos cuidados na utilização de substratos flexíveis (e.g. polietileno tereftalato PET). A estrutura empregada é composta por vidro, óxido de índio dopado com estanho (ITO), poli(3,4- etilenodioxitiofeno) complexado com poli(ácido estireno-sulfônico) (PEDOT:PSS), P3HT:PCBM, fluoreto de lítio (LiF) e alumínio. PET coberto por In2O3/Au/Ag em substituição ao vidro-ITO é utilizado devido à busca da indústria eletrônica por materiais alternativos de baixo custo. Estrutura semelhante é empregada para caracterização da mobilidade dos portadores de carga em filmes orgânicos. Técnicas tais como Time of Flight (ToF), Charge Extraction in Linearly Increasing Voltage (CELIV), além da interpretação de curvas estacionárias de densidade de corrente por tensão (JxV) foram empregadas para estudo de derivados de poli(para-fenileno vinileno) (PPV). Foram obtidas mobilidades de 10-810-6 cm2/Vs para modelos de corrente limitada por carga espacial (SCLC) com armadilhas rasas e profundas. Mobilidades de efeito de campo caracterizadas em TFTs bottom gate bottom contact com porta comum são pelo menos duas ordens de grandeza superiores às obtidas através das técnicas anteriormente citadas. Foram utilizados diversos substratos (e.g. silício monocristalino e vidro-ITO), dielétricos (e.g. oxinitreto de silício (SiOxNy) por PECVD e SiO2 térmico), tratamentos de superfície (e.g. vapor de hexametildissilazana HMDS), semicondutores (derivados de PPV, P3HT, pentaceno) e eletrodos (e.g. camada de aderência de titânio). Definiu-se assim uma metodologia de seleção de novos semicondutores orgânicos para a indústria eletrônica.In this work, it is presented a methodology for organic thin-film transistor (OTFT) fabrication. Poly(3-hexylthyophene) (P3HT):[6,6]-phenyl-C61-butyric acidmethyl ester (PCBM) bulk heterojunction solar cells were studied for their maximum power conversion efficiency (PCE) around 5 %. Efficiencies evolution in time from 10-6 to 1.7 % show the difficulties involved in organic thin-film processing and device characterization. It is of remarkable importance the electrodes geometry, the organic blend solution preparation and the extra-care while processing on flexible substrates (e.g. polyethylene terephthalate PET). Devices are composed of indium tin oxide covered glass, poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonic acid) (PEDOT:PSS), P3HT:PCBM active layer, lithium fluoride (LiF) and aluminum. PET covered with In2O3/Au/Ag substituting glass-ITO was employed due to the electronic industry research for low cost alternative materials. Similar structure is used for charge carrier mobility characterization. Techniques such as Time of Flight (ToF), Charge Extraction in Linearly Increasing Voltage (CELIV), and charge transport modeling of current density vs. voltage (JxV) stationary curves were applied on semiconductors like poly(para-phenylene vinylene) (PPV) derivatives. Mobilities around 10-810-6 cm2/Vs for space charge limited current (SCLC) with shallow and deep traps were obtained. Field effect mobilities characterized in bottom gate bottom contact TFTs with common gate are at least two orders higher than previous values. During this work, it was tested different substrates (e.g. monocrystalline silicon and glass-ITO), insulators (e.g. PECVD silicon oxynitride and thermal SiO2), surface treatments (e.g. hexamethyldisilazane vapor), semiconductors (PPV derivatives, P3HT, pentacene) and electrodes (e.g. titanium adhesion layer). It was defined that way a methodology of new semiconducting material selection for the electronic industry.