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Synthesis and Ligand Engineering of Colloidal Metal Chalcogenide Nanoparticles for Scalable Solution Processed PhotovoltaicsRyan Gupta Ellis (9175325) 09 September 2022 (has links)
<p>As global population continue to
rise, the demand for energy is slated to increase substantially. To combat
climate change, large amounts of renewable energy will be needed to feed this
growing demand. Of renewable energy sources, photovoltaics are well positioned
to meet this increasing demand due to the immense abundance of solar energy
incident on earth. However, existing energy intensive, low throughput, and
costly manufacturing techniques for photovoltaics may pose a barrier to
continued large scale implementation.</p>
<p>Solution processing has emerged as
a promising photovoltaics fabrication technique with high throughput, high
materials utilization, and lower cost than existing vacuum-based methods. Thin
film photovoltaic materials such as Cu(In,Ga)(S,Se)<sub>2</sub> and CdTe have
both been fabricated using various solution processing methods. Of the various
solution processing routes, colloidal metal chalcogenide nanoparticles have
demonstrated promise as a hydrazine-free route for the solution processing of
high efficiency Cu(In,Ga)(S,Se)<sub>2</sub> solar cells. However, conventional
solution processing with colloidal nanoparticles has long suffered from anionic
and carbonaceous impurities, stemming from legacy synthesis methods. The work
in this dissertation aims to solve these issues through the development of
novel synthetic methods, ligand engineering, and ultimately improved
scalability through slot-die coating.</p>
<p> Typical colloidal syntheses rely on the use of
metal salts as precursors such as metal halides, nitrates, acetates, and so forth,
where the anions may incorporate and alter the electrical properties of the
targeted nanomaterials. In this work, the recent advances in amine-thiol
chemistry and its unique ability to solubilize many metal containing species
are expanded upon. Alkylammonium metal thiolate species are easily formed upon
addition of monoamine and dithiol to elemental Cu, In, Ga, Sn, Zn, Se, or metal
chalcogenides such as Cu<sub>2</sub>S and Ag<sub>2</sub>S. These species were
then used directly for the synthesis of colloidal nanoparticles without the
need for any additional purification. The metal thiolate thermal decomposition
pathway was studied, verifying that only metal chalcogenides and volatile
byproducts are formed, providing a flexible route to compositionally uniform,
phase pure, and anionic impurity-free colloidal nanoparticles including
successful syntheses of In<sub>2</sub>S<sub>3</sub>, (In<sub>x</sub>Ga<sub>1–x</sub>)<sub>2</sub>S<sub>3</sub>,
CuInS<sub>2</sub>, CuIn(S<sub>x</sub>Se<sub>1–x</sub>)<sub>2</sub>, Cu(In<sub>x</sub>Ga<sub>1–x</sub>)S<sub>2</sub>,
Cu<sub>2</sub>ZnSnS<sub>4</sub>, and AgInS<sub>2</sub>. </p>
<p>However, further impurities from deleterious carbonaceous
residues originating from long chain native ligands were still a persistent
problem. This impurity carbon has been observed to hinder grain formation
during selenization and leave a discrete residue layer between the absorber
layer and the back contact. An exhaustive hybrid organic/inorganic ligand
exchange was developed in this work to remove tightly bound oleyalmine ligands
through a combination of microwave-assisted solvothermal pyridine ligand
stripping followed by inorganic capping with diammonium sulfide, yielding greater
than 98% removal of native ligands via a rapid process. Despite the aggressive
ligand removal, the nanoparticle stoichiometry remained largely unaffected when
making use of the hybrid ligand exchange. Scalable blade coating of the ligand
exchanged nanoparticle inks from non-toxic dimethyl sulfoxide inks yielded remarkably
smooth and crack free films with RMS roughness less than 7 nm. Selenization of
ligand exchanged nanoparticle films afforded substantially improved grain
growth as compared to conventional non-ligand exchanged methods yielding an
absolute improvement in device efficiency of 2.8%. Hybrid ligand exchange
nanoparticle-based devices reached total-area power conversion efficiencies of
12.0%.</p>
<p>While extremely effective in ligand removal, ligand exchange
pathways increase process complexity and solvent usage substantially, which may
limit the cost advantage solution processing aims to provide. Further synthesis
improvement was developed through a ligand exchange free, direct sulfide capped
strategy. Using sulfolane as a benign solvent, CuInS<sub>2</sub> nanoparticles
with thermally degradable thioacetamide ligands were synthesized using thermal
decomposition of isolated metal thiolates from Cu<sub>2</sub>S and In
precursors. Through gentle thermal treatment, these ligands decomposed into
non-contaminating gaseous byproducts leaving carbon free nanoparticle films
without the need for ligand exchange.</p>
<p>With the development of virtually contamination free
colloidal nanoparticle inks, focus was shifted to scalability using slot die
coating. Unlike typical lab-scale coating techniques such as spin coating, slot
die coating is a widely used industrial coating technique with nearly 100%
materials utilization, and high throughput roll-to-roll compatibility. A custom
lab-scale slot-die coater was used to rapidly proof coating conditions, which
were rapidly analyzed for uniformity using absorbance scanning in conjunction
with profilometry. A cosolvent chlorobenzene/dichlorobenzene ink was developed
to yield highly uniform, crack free thin films from non-ligand-exchanged
Cu(In,Ga)S<sub>2</sub> nanoparticles, which were finished into devices with
champion total are efficiencies of 10.7%. To the best of our knowledge, this
represents the first report of slot die coated Cu(In,Ga)(S,Se)<sub>2</sub>
photovoltaics. The methods presented in this work offer a pathway towards low
impurity, high efficiency, scalable solution processed Cu(In,Ga)(S,Se)<sub>2</sub>
photovoltaics to enable low cost renewable energy.</p>
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Designing hypercyclic replicating networksWood, Evan A. January 2007 (has links)
In the last 20 years there has been a number of synthetic and natural product based molecular replicators published in the literature. The majority of these systems have focused on the minimal model with only a few examples of cross-catalytic or reciprocal replication. Of the cross-catalytic systems investigated the majority focus around the use of natural products, oligonucleotides, peptides etc. This thesis will investigate the design, synthesis and kinetic analysis of both synthetic minimal and reciprocal replicating systems, and how these two forms of replication interact in a complex hypercyclic network. Chapter 1 introduces key concepts such as molecular recognition, intramolecularity/ enzyme kinetic, bisubstrate systems and the work conducted into replication systems to date. Chapter 2 describes the design, synthesis and kinetic analysis of a reciprocal replicating system, based on Diels-Alder and 1,3-dipolar cycloadditions, before going on to discuss what we have learned and how this system can be improved. Chapter 3 focuses on the design, synthesis and kinetic analysis of a replicating network (minimal and reciprocal replication), based on 1,3-dipolar cycloadditions. Initial individual systems are examined in isolation to determine their behavior and nature. After which the systems are combined to observe how each species interacts in a potential complex hypercyclic network. Chapter 4 investigates the redesign of the replicating network in Chapter 3 in order to overcome the problems identified from its kinetic analysis. Chapter 5 introduces the shift in direction away from kinetically controlled replicating networks towards systems in thermodynamic equilibrium.
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Nanochemische Zusammensetzungsanalyse mittels anomaler Röntgenkleinwinkelstreuung (ASAXS)Haas, Sylvio 11 October 2010 (has links)
Im Rahmen der vorliegenden Arbeit wurde eine Auswertemethodik für anomale Röntgenkleinwinkelstreuung (ASAXS) zur nanochemischen Zusammensetzungsanalyse der beteiligten Phasen eines Probensystems entwickelt und auf eine Glaskeramik angewendet. Die nanochemische Analyse unterscheidet sich von den bekannten Verfahren der partiellen Strukturfaktoren bzw. -funktionen (PSF) durch die Anwendbarkeit auf nahezu jedes Probensystem, da keine einschränkenden Annahmen bezüglich der anomalen Korrekturfaktoren der atomaren Streufaktoren der einzelnen Elemente getroffen werden müssen. Im Gegensatz zu den üblicherweise verwendeten PSF''s werden die relevanten Probeneigenschaften, d.h. die Nanostruktur und die nanochemische Zusammensetzung, direkt aus den Verläufen der differenziellen Streuquerschnitte in Abhängigkeit von der Röntgenenergie und des Streuvektorbetrages bestimmt. Es wurden umfangreiche anomale Röntgenkleinwinkelstreuexperimente an einer ausgewählten Oxyfluorid-Glaskeramik durchgeführt und mit der entwickelten Methode analysiert. Die untersuchte Glaskeramik, welche mit den seltenen Lanthanoiden Erbium und Ytterbium dotiert ist, zeigt die nichtlineare optische Eigenschaft der Frequenzerhöhung. Es konnte gezeigt werden, dass es möglich ist, die gemittelte Zusammensetzung der Teilchenphase und die der amorphen Glasmatrix mittels ASAXS quantitativ zu bestimmen. Im Gegensatz zu EDX-Studien liefert ASAXS gemittelte Zusammensetzungen, die das Probensystem aus statistischer Sicht besser repräsentieren. Die nanochemische Zusammensetzungsanalyse der Glaskeramik lieferte das Ergebnis, dass das Cadmium kein Bestandteil der Nanopartikelphase ist, die eine gemittelte Zusammensetzung von 17%Pb 2%Er 17%Yb 64%F (at%) aufweist. TEM-Studien implizieren, dass die Nanopartikel im Glas näherungsweise als Rotationsellipsoide beschrieben werden können. Es wurde gezeigt, dass die Streukurven der ASAXS Studien mit einem solchen Strukturmodell modelliert werden können. / In the present work an evaluation method for anomalous small-angle X-ray scattering (ASAXS) to analyze nanochemical compositions of all involved phases of a sample has been developed and was applied to a glass ceramic. The nanochemical analysis differs from the known methods of partial structure factors or functions (PSF) by the applicability to virtually any system, because the new evaluation method does not require any limiting assumptions regarding the anomalous corrections of the atomic scattering factors of the individual elements. Unlike the PSF''s normally used, the relevant sample properties, i.e. nanostructure and nanochemical compostion, will be determined directly from the differential scattering cross sections as a function of the X-ray energy and the scattering vector. Extensive ASAXS experiments at a selected oxyfluoride glass ceramic were done and analyzed by the developed method. The investigated glass ceramic, which is co-doped with selected lanthanides like erbium and ytterbium, shows the nonlinear optical property of frequency upconversion. It was shown that it is possible to determine quantitatively the average compositions of all phases of a system using ASAXS. In contrast to EDX studies, ASAXS provides average compositions, which represent the sample better from a statistical point of view. The nanochemical composition analysis of the glass ceramic yielded the result that the cadmium is not part of the nanoparticle phase, which has an average composition of 17%Pb 2%Er 17%Yb 64%F (at%). TEM studies imply that the nanoparticles in the glass can be described by ellipsoids. It was shown that the scattering curves of the ASAXS studies can be simulated by such a structural model.
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Phenolic resin/polyhedral oligomeric silsesquioxane (POSS) hybrid nanocomposites and advanced composites for use as anode materials in lithium ion batteriesLee, Sang Ho, January 2007 (has links)
Thesis (M.S.)--Mississippi State University. Department of Chemistry. / Title from title screen. Includes bibliographical references.
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Chemical incorporation of polyhedral oligomeric silsesquioxane into thermoset matricesCho, Hosouk, January 2006 (has links)
Thesis (Ph.D.) -- Mississippi State University. Department of Chemistry. / Title from title screen. Includes bibliographical references.
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A Scattering-based Approach to the Design, Analysis, and Experimental Verification of Magnetic Metamaterials Made from DielectricsWheeler, Mark Stephen 01 September 2010 (has links)
The design, modeling, fabrication, and validation of an optical magnetic response in dielectric-based metamaterials are studied. These metamaterials consist of either periodic or random arrays of dielectric particle inclusions, which may be spheres, coated spheres, or completely randomly shaped. It is demonstrated that because of the simple particle shapes and dielectric materials, these metamaterials are quite easy and feasible to implement in a bulk, three-dimensional sample, and the response is isotropic. This in is contrast to other predominant designs of optical metamaterials, which are planar and anisotropic arrays of complicated metallic fishnet or split-ring resonator structures, which require stringent tolerances and sophisticated assembly. It is shown that SiC is one of many materials from which such infrared magnetic metamaterials can be constructed. A simple SiC powder is used to verify these claims. The milled micropowder of crystalline SiC is comprised of particles of random shapes and sizes. A model of the electromagnetic response of such powders is developed, whereby the induced magnetic dipole response is modeled by equivalently-sized spheres of SiC, whereas the electric dipole response is modeled by a continuous distribution of ellipsoidal particles. Infrared spectroscopic measurements and numerical calculations are performed, verifying both the magnetic and electric response of the powder. A alternate approach is also described, where uniform SiC microspheres are fabricated using more sophisticated nanochemical techniques. In the final portion of the dissertation, the mutual near-field coupling between ideal magnetic dipoles induced in dielectric spheres is studied. This is implemented for microwave frequencies using large permittivity ceramic spheres. An approximate coupled dipole model of the multiple scattering among the spheres is developed, and a transition matrix method is implemented to calculate the exact scattering by the clusters. Experimental measurements are performed, confirming the two models. The results for pairs, chains, and rings of spheres indicates that the magnetic dipole modes hybridize in analogy to atomic bonding. A notable result is that certain hybridized magnetic dipole modes may have a net electric dipole moment. The similarity to atomic and molecular bonding should prove useful in conceptualizing and designing more sophisticated metamaterials.
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A Scattering-based Approach to the Design, Analysis, and Experimental Verification of Magnetic Metamaterials Made from DielectricsWheeler, Mark Stephen 01 September 2010 (has links)
The design, modeling, fabrication, and validation of an optical magnetic response in dielectric-based metamaterials are studied. These metamaterials consist of either periodic or random arrays of dielectric particle inclusions, which may be spheres, coated spheres, or completely randomly shaped. It is demonstrated that because of the simple particle shapes and dielectric materials, these metamaterials are quite easy and feasible to implement in a bulk, three-dimensional sample, and the response is isotropic. This in is contrast to other predominant designs of optical metamaterials, which are planar and anisotropic arrays of complicated metallic fishnet or split-ring resonator structures, which require stringent tolerances and sophisticated assembly. It is shown that SiC is one of many materials from which such infrared magnetic metamaterials can be constructed. A simple SiC powder is used to verify these claims. The milled micropowder of crystalline SiC is comprised of particles of random shapes and sizes. A model of the electromagnetic response of such powders is developed, whereby the induced magnetic dipole response is modeled by equivalently-sized spheres of SiC, whereas the electric dipole response is modeled by a continuous distribution of ellipsoidal particles. Infrared spectroscopic measurements and numerical calculations are performed, verifying both the magnetic and electric response of the powder. A alternate approach is also described, where uniform SiC microspheres are fabricated using more sophisticated nanochemical techniques. In the final portion of the dissertation, the mutual near-field coupling between ideal magnetic dipoles induced in dielectric spheres is studied. This is implemented for microwave frequencies using large permittivity ceramic spheres. An approximate coupled dipole model of the multiple scattering among the spheres is developed, and a transition matrix method is implemented to calculate the exact scattering by the clusters. Experimental measurements are performed, confirming the two models. The results for pairs, chains, and rings of spheres indicates that the magnetic dipole modes hybridize in analogy to atomic bonding. A notable result is that certain hybridized magnetic dipole modes may have a net electric dipole moment. The similarity to atomic and molecular bonding should prove useful in conceptualizing and designing more sophisticated metamaterials.
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Investigação da estabilidade de fases da zircônia-escândia / Investigation of phase stability in the scandia-zirconiaGROSSO, ROBSON L. 25 August 2016 (has links)
Submitted by Marco Antonio Oliveira da Silva (maosilva@ipen.br) on 2016-08-25T17:43:02Z
No. of bitstreams: 0 / Made available in DSpace on 2016-08-25T17:43:02Z (GMT). No. of bitstreams: 0 / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Nesse trabalho foi proposto investigar a estabilidade de fases do sistema zircônia-escândia (ScSZ) por meio do estudo termodinâmico de nanopartículas, na faixa de 0 a 20% em mol de Sc2O3, e a partir da introdução de um segundo aditivo (Dy2O3 e Nb2O5) ao ZrO2 contendo 10% em mol de Sc2O3 (10ScSZ). A estabilidade de fases do ScSZ foi avaliada com base em dados termodinâmicos determinados pelas técnicas de microcalorimetria de adsorção de água e calorimetria de dissolução à alta temperatura. As soluções sólidas foram sintetizadas pelo método de coprecipitação de hidróxidos. Dados termodinâmicos foram determinados para as formas polimórficas encontradas (monoclínica, tetragonal, cúbica, romboédrica β e γ) por difração de raios X no ScSZ. Esse trabalho resultou no diagrama de fases em nanoescala de tamanho de partícula-composição. Os efeitos produzidos pela introdução de aditivos na matriz de 10ScSZ foram investigados visando obter a possível estabilização da estrutura cúbica (c) e a supressão da transformação de fase c-β, característica do sistema binário. As composições foram sintetizadas por coprecipitação de hidróxidos e por reações em estado sólido para fins comparativos. Os materiais foram sinterizados convencionalmente e por sinterização assistida por campo elétrico. A estabilização completa da fase cúbica ocorreu a partir de teores molares de 1% de Dy2O3 e 0,5% de Nb2O5. O menor teor de Nb2O5 necessário para a estabilização da fase foi atribuído à provável formação da fase líquida durante a sinterização e ao menor tamanho do íon Nb5+. Os resultados de difratometria de raios X em alta temperatura e análise térmica mostraram que houve supressão da transição c-β. As amostras contendo 0,5% mol de Nb2O5 apresentaram valores de condutividade iônica similares aos do 10ScSZ sem aditivos em uma ampla faixa de temperatura com elevada estabilidade em um período de 170 h a 600 °C. / Tese (Doutorado em Tecnologia Nuclear) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP / FAPESP: 12/03319-5
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Structural and optoelectronic studies of lead chalcogenide thin films and nanocrystalsAkhtar, Javeed January 2010 (has links)
The work described herein deals with the synthesis and characterization of lead chalcogenide thin films and nanocrystals. The first part of thesis describes the properties of semiconductors followed by an analysis on the chemical vapour deposition and nanoparticulate formation. In the next part of thesis, single-source precursors of type thioselenophosphinato, selenoureato, dithiocarbamato and dithiocarbanato complexes of lead have been synthesised and characterised. As-synthesised compounds have been utilised for the fabrication of lead sulfide and lead selenide thin films by aerosol-assisted chemical vapour deposition as well as nanocrystals by colloidal injection method. Lead sulfide thin films were also deposited by liquid-liquid interface from lead dithiocarbanato at room temperature. The as grown thin films of lead sulfide and lead selenide have been characterised by XRD, SEM and energy dispersive x-ray (EDX) analysis. In the second part of the thesis, preparation of lead sulfide and lead selenide nanocrystals in olive oil at low growth temperatures (50-60°C) is described and have shown that by controlling experimental conditions, well-defined particles with tunable emission in mid and far-infrared region can be synthesised. Furthermore, compositionally-tuned PbSxSe1-x nanocrystals has also been prepared by adding controlled amount of sulur and selenium ingredients into lead oxide. Homogenous distribution of sulfur and selenium within alloyed nanocrystals is confirmed by transmission electron microscope studies. Moreover, attempts have been made to prepare quaternary (PbTe/Se/S) nanocrystals of lead chalcogenides and depth (1.9-5.8 nm) profile analysis by x-ray photoelectron spectroscopy confirmed the formation of core/shell/shell type structure i.e. PbTe/S/Se.
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Synthèse et étude d'édifices polynucléaires nanométriques de Ruthénium et de Cuivre basés sur des ligands polyazaaromatiquesServaty, Kathleen 18 January 2011 (has links)
Depuis les années quatre-vingt, la construction d’édifices supramoléculaires à base de complexes de coordination suscite un intérêt considérable dans la recherche de nouveaux nanomatériaux fonctionnels. L’utilisation de complexes métalliques permet non seulement l’obtention d’une multitude de supramolécules de géométrie et de dimensionnalité très variées, mais également l’introduction de processus remarquables au sein des entités nanométriques, comme par exemple le transfert d’énergie lumineuse, le transport d’électrons et la séparation photo-induite de charges. La recherche menée au cours de cette thèse s’est plus particulièrement focalisée sur l’étude de deux types d’édifices supramoléculaires polymétalliques de dimensions différentes, l’un tridimensionnel, construit au départ d’ions ruthénium (II), l’autre unidimensionnel, obtenu à partir d’ions cuivre (II) ou cuivre (I).<p><p>Plus précisément, la première partie de ce travail a été consacrée à la synthèse d’un complexe hexanucléaire symétrique de Ru(II), à base de ligands pontants PHEHAT et TPAC, afin de développer de nouvelles antennes collectrices d’énergie lumineuse. Dans ce cadre, nos travaux se sont principalement concentrés sur la synthèse ainsi que sur l’étude électrochimique et photophysique de deux nouveaux composés précurseurs trinucléaires, le cis-{[(phen)2Ru(PHEHAT)]2Ru(CH3CN)2}6+ et le {[(phen)2Ru(PHEHAT)]2Ru(TPAC)}6+, pouvant également servir de bloc de construction pour l’élaboration d’entités de tailles encore plus importantes. Une analyse par spectrométrie de masse du produit obtenu par chélation de l’entité bis-CH3CN sur le composé trinucléaire à base de TPAC ne nous a pas permis de prouver la présence de l’entité hexanucléaire. La nature du composé identifié semble toutefois confirmer la formation de l’espèce souhaitée à un moment ou un autre. <p><p>La seconde partie de notre travail a consisté à tester le TPAC ainsi que deux ligands dérivés du dipyrrométhène (m-DipyH et m-dpDipyH) comme agents pontants pour la construction de nouveaux complexes polynucléaires cuivrés unidimensionnels. D’une part, nous nous sommes penchés sur la synthèse des sous-unités monométalliques [Cu(II)(Dipy)2]0, [Cu(II)(dpDipy)2]0 et [Cu(I)(dpDipy)2]-. L’ensemble des études réalisées sur les deux composés mononucléaires de Cu(II) a permis la mise en évidence de propriétés extrêmement différentes de celles des complexes de Cu(II) polypyridiniques, tant du point de vue structural, qu’électrochimique et photophysique. Par ailleurs, les analyses consacrées à la caractérisation du [Cu(I)(dpDipy)2]- ont révélé de manière surprenante un comportement instable pour cette entité, à l’inverse des complexes de Cu(I) à base de phénanthrolines « encombrées ». Le recours à des calculs théoriques nous a permis de proposer une hypothèse pouvant expliquer cette différence de comportement. D’autre part, bien que des incertitudes subsistent toujours quant à la possibilité de former des entités polynucléaires à base de Cu(II) et de TPAC, les résultats obtenus par spectrométrie de masse ont clairement prouvé l’obtention d’espèces de Cu(II) de très haute nucléarité au départ du m-DipyH. Les ligands pontants dérivés du dipyrrométhène se révèlent donc être de très bons candidats pour l’élaboration d’entités unidimensionnelles de Cu(II). Celles-ci pourraient susciter un grand intérêt dans le cadre d’une application impliquant l’utilisation de la lumière, en raison des propriétés d’absorption et de luminescence intéressantes détectées pour les sous-unités monométalliques de Cu(II). <p> / Doctorat en Sciences / info:eu-repo/semantics/nonPublished
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