With growing world population and decreasing fossil fuel reserves we need to explore and utilize variety of renewable and clean energy sources to meet the imminent challenge of energy crisis. Solar energy is considered as the leading promising alternate energy source with the pertinent challenge of off sunshine period and uneven worldwide distribution of usable sun light. Although thermoelectricity is considered as a reasonable energy harvester from wasted heat, its mass scale usage is yet to be developed. By transforming window glasses into generators of thermoelectricity, this doctoral work explores engineering aspects of using the temperature gradient between the hot outdoor heated by the sun and the relatively cold indoor of a building for mass scale energy generation. In order to utilize the two counter temperature environments simultaneously, variety of techniques, including: a) insertion of basic metals like copper and nickel wire, b) sputtering of thermoelectric films on side walls of individual glass strips to form the thickness depth of the glass on subsequent curing of the strips, and c) embedding nano-manufactured thermoelectric pillars, have been implemented for innovative integration of thermoelectric materials into window glasses. The practical demonstration of thermoelectric windows has been validated using a finite element model to predict the behavior of thermoelectric window under variety of varying conditions. MEMS based characterization platform has been fabricated for thermoelectric characterization of thin films employing van der Pauw and four probe modules. Enhancement of thermoelectric properties of the nano- manufactured pillars due to nano-structuring, achieved through mechanical alloying of micro-sized thermoelectric powders, has been explored. Modulation of thermoelectric properties of the nano-structured thermoelectric pillars by addition of sulfur to nano-powder matrix has also been investigated in detail. Using the best possible p and n type thermoelectric materials, this novel energy generation technique promises 304 watts of thermoelectricity from a 9 m2 glass window utilizing temperature difference of 20 OC. In addition to be useful even during off sunshine hours of the day, these energy harvesting windows will be capable of power generation even in the absence of a cooling systems inside the building as long as a natural temperature gradient exists between the two counter environments. With an increasing trend of having the exterior of buildings and high rises entirely made up of glass, this work offers an innovative transformation of these building exteriors into mass scale energy harvesters capable of running average lighting loads inside the building hence providing a complimentary source of electricity to the main power grid.

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Commercially available high-performance thermoelectric materials are often rare or toxic and therefore unsustainable. The present thesis work makes a case for eco-friendly, earth-abundant, and non-toxic p-type ceramic Cu2SnS3 (CTS, hereafter) and, in general, the use of disordered materials for thermoelectric applications. The detailed study of polymorphism, synthesis conditions, porosity, grain size, and doping provides a systematic and in-depth experimental and computational analysis of thermoelectric properties and stability of CTS. These results can be generalized for numerous thermoelectric materials and other applications. Moreover, a case for functioning thermoelectric generators using non-toxic and cost-effective materials is also presented. The thesis begins with a brief introduction to thermoelectricity, followed by a literature review and justification of the choice of the subject. The second chapter puts forward a novel approach to stabilize a disordered CTS polymorph without any chemical alteration through high-energy reactive ball milling. The third chapter deals with the stability of disordered samples under different synthesis and sintering conditions, highlighting the effect of synthesis environment, microstructure, and porosity. The fourth chapter employed a novel, facile, and cost-effective two-step synthesis method (high-energy ball milling combined with spark plasma sintering) to synthesize CTS bulk samples. The two-step synthesis method was able to constrain the CTS grain growth in the nanometric range, revealing the conductive nature of the CTS surfaces. The next chapter explores combining the two-step synthesis method with Ag substitution at the Sn lattice site to improve CTS's thermoelectric performance further. In the final stages of the thesis work, thin film thermoelectric generators were fabricated using CTS and similar chalcogenides, demonstrating power output comparable to existing thermoelectric materials used in the medium temperature range. The final chapter summarizes outlooks and future perspectives stemming from this research work.

Os materiais cerâmicos termoelétricos preparados a partir de ligas de SiGe, são utilizados em Geradores de Potência a Radioisótopos (GTR), na conversão de energia por efeitos termoelétricos. Neste trabalho de pesquisa foram estudadas as condições de preparação destas cerâmicas a partir de ligas de Silício-Germânio. Visou-se, portanto obter a melhor eficiência, pela otimização da \"Fator de Mérito\" (ou Número de loffe) , através dos processos de preparação e tratamentos térmicos da liga, e também na dopagem das cerâmicas. As ligas de silício-germânio (Si80Ge20) foram obtidas pela técnica de crescimento Czochralski, com campo elétrico aplicado (ECZ) e também por outras técnicas de fusão e solidificação, para comparação. Amostras com homogeneidade satisfatória foram quebradas e moídas para processamento cerâmico. E em seguida o pó da liga foi então dopado, misturando-se este com pó de boro amorfo e depois prensado, a fim de se obter elementos cerâmicos semicondutores tipo-p, com propriedades termoelétricas para altas temperaturas (&#8776 1000&#176C). A sinterização foi feita por três técnicas diferentes: pela técnica dos Pós Discretos ou PIES (Pulverized and Intermixed Elements of Sintering), pelo procedimento cerâmico convencional, e pela Prensagem a Quente (HotPressing), sendo esta última usada como padrão de comparação. As amostras obtidas foram analisadas e caracterizadas por técnicas convencionais de caracterização cerâmica tais como: medidas da densidade, dos tamanhos dos grãos, porosidade, área superficial, etc. e também por medidas de alguns dos parâmetros físicos que influenciam diretamente na eficiência termoelétrica tais como: coeficiente Seebeck, calor específico e parâmetro de rede, para ligas de composição nominal Si80Ge20 sem e com dopantes para semicondutores tipo-p. Uma amostra preparada pela General Electric usando a técnica de Prensagem a Quente (Hot-Pressing), foi usada como padrão de comparação. A liga obtida pela técnica ECZ apresentou boa homogeneidade. Foi encontrado que a qualidade microestrutural das cerâmicas tais como: densidade, a regularidade e a composição química dos grãos das cerâmicas depende muito da técnica de processamento. Estes elementos cerâmicos termoelétricos poderão ser usados como fonte de energia em Geradores de Potência Termoelétrica a Radioisótopos (GTR) mais especificamente na alimentação de satélites brasileiros fabricados pelo Centro Técnico Aeroespacial (CTA) junto com o Instituto de Estudos Avançados (IEAv) através da Divisão de Energia Nuclear (IEAvENU) deste Instituto, ou entre outras aplicações para fins militares e civil / Doped ceramics elements, prepared from Si-Ge alloy are used in Radioisotopic Thermoelectric Generators (GTR) for energy conversion by thermoelectrical effects. In this research the experimentais conditions to prepare thermoeletric ceramics from Silicon-Germanium alloys have been determined. The purpose was to get the best efficiency, by optimization of the \"Merit Figure\" (or \"loffe Number\'), using different preparation methods and thermal treatments of alloys, as well as the doping of these ceramics. Silicon-Gemanium alloys (Si80Ge20) have been grown by the Czochralski technique under applied eletric field (ECZ) , as well as by others fusion techniques for comparison. Afier the fusion of the alloy, samples with satisfactory homogeneity have been smashed and milled for ceramic processing. Powder of Si-Ge alloy was then heavely doped by mixing with amorphous boron powder and pressed to get type-P semiconductor thermoelectrical ceramics elements, at high temperatures (&#8776 1000 &#176C). The sintering was made by three differents techniques: PIES method (Pulverized and Intermixed Elements of Sintering), convencional ceramic processing, and Hot-Pressing sintering, for comparison. The samples have been analyzed and characterized by conventional ceramics technique such as: determination of density, grain size, porosity, surface area, etc. and measuring toa some physical parameters that affect directly the thermoelectrical efficiency such as: Seebeck coefficient, specific heat and lattice parameter to Silicon-Germanium alloys with nominal composition Si80Ge20 with or without dopings to type-P semiconductors. A sample prepared by General Electric Company using the Hot-Pressing technique was used as standard. The alloy grown by ECZ technique showed a good homogeneity. It was found that the microstructural quality of the ceramics such as: density, grains regularity and chemical composition of the ceramics depend of the ceramic processing technique. These thermoelectrical elements can be used as power supply for the Brazilian satellites made by the Centro Técnico Aeroespacial (CTA) together with the Instituto de Estudos Avançados (IEAv) through the Divisão de Engenharia Nuclear (ENU) , and among other applications for military and civil purposes

Os materiais cerâmicos termoelétricos preparados a partir de ligas de SiGe, são utilizados em Geradores de Potência a Radioisótopos (GTR), na conversão de energia por efeitos termoelétricos. Neste trabalho de pesquisa foram estudadas as condições de preparação destas cerâmicas a partir de ligas de Silício-Germânio. Visou-se, portanto obter a melhor eficiência, pela otimização da \"Fator de Mérito\" (ou Número de loffe) , através dos processos de preparação e tratamentos térmicos da liga, e também na dopagem das cerâmicas. As ligas de silício-germânio (Si80Ge20) foram obtidas pela técnica de crescimento Czochralski, com campo elétrico aplicado (ECZ) e também por outras técnicas de fusão e solidificação, para comparação. Amostras com homogeneidade satisfatória foram quebradas e moídas para processamento cerâmico. E em seguida o pó da liga foi então dopado, misturando-se este com pó de boro amorfo e depois prensado, a fim de se obter elementos cerâmicos semicondutores tipo-p, com propriedades termoelétricas para altas temperaturas (&#8776 1000&#176C). A sinterização foi feita por três técnicas diferentes: pela técnica dos Pós Discretos ou PIES (Pulverized and Intermixed Elements of Sintering), pelo procedimento cerâmico convencional, e pela Prensagem a Quente (HotPressing), sendo esta última usada como padrão de comparação. As amostras obtidas foram analisadas e caracterizadas por técnicas convencionais de caracterização cerâmica tais como: medidas da densidade, dos tamanhos dos grãos, porosidade, área superficial, etc. e também por medidas de alguns dos parâmetros físicos que influenciam diretamente na eficiência termoelétrica tais como: coeficiente Seebeck, calor específico e parâmetro de rede, para ligas de composição nominal Si80Ge20 sem e com dopantes para semicondutores tipo-p. Uma amostra preparada pela General Electric usando a técnica de Prensagem a Quente (Hot-Pressing), foi usada como padrão de comparação. A liga obtida pela técnica ECZ apresentou boa homogeneidade. Foi encontrado que a qualidade microestrutural das cerâmicas tais como: densidade, a regularidade e a composição química dos grãos das cerâmicas depende muito da técnica de processamento. Estes elementos cerâmicos termoelétricos poderão ser usados como fonte de energia em Geradores de Potência Termoelétrica a Radioisótopos (GTR) mais especificamente na alimentação de satélites brasileiros fabricados pelo Centro Técnico Aeroespacial (CTA) junto com o Instituto de Estudos Avançados (IEAv) através da Divisão de Energia Nuclear (IEAvENU) deste Instituto, ou entre outras aplicações para fins militares e civil / Doped ceramics elements, prepared from Si-Ge alloy are used in Radioisotopic Thermoelectric Generators (GTR) for energy conversion by thermoelectrical effects. In this research the experimentais conditions to prepare thermoeletric ceramics from Silicon-Germanium alloys have been determined. The purpose was to get the best efficiency, by optimization of the \"Merit Figure\" (or \"loffe Number\'), using different preparation methods and thermal treatments of alloys, as well as the doping of these ceramics. Silicon-Gemanium alloys (Si80Ge20) have been grown by the Czochralski technique under applied eletric field (ECZ) , as well as by others fusion techniques for comparison. Afier the fusion of the alloy, samples with satisfactory homogeneity have been smashed and milled for ceramic processing. Powder of Si-Ge alloy was then heavely doped by mixing with amorphous boron powder and pressed to get type-P semiconductor thermoelectrical ceramics elements, at high temperatures (&#8776 1000 &#176C). The sintering was made by three differents techniques: PIES method (Pulverized and Intermixed Elements of Sintering), convencional ceramic processing, and Hot-Pressing sintering, for comparison. The samples have been analyzed and characterized by conventional ceramics technique such as: determination of density, grain size, porosity, surface area, etc. and measuring toa some physical parameters that affect directly the thermoelectrical efficiency such as: Seebeck coefficient, specific heat and lattice parameter to Silicon-Germanium alloys with nominal composition Si80Ge20 with or without dopings to type-P semiconductors. A sample prepared by General Electric Company using the Hot-Pressing technique was used as standard. The alloy grown by ECZ technique showed a good homogeneity. It was found that the microstructural quality of the ceramics such as: density, grains regularity and chemical composition of the ceramics depend of the ceramic processing technique. These thermoelectrical elements can be used as power supply for the Brazilian satellites made by the Centro Técnico Aeroespacial (CTA) together with the Instituto de Estudos Avançados (IEAv) through the Divisão de Engenharia Nuclear (ENU) , and among other applications for military and civil purposes

No description available.

The search for renewable energy resources and ways to harvest them has become a global mainstream topic among researchers nowadays, with solar cells and thermoelectric generators among the energy harvesting technologies currently being researched in vast. CZTS (Cu2ZnSnS4), a p-type semiconducting material initially researched to replace copper indium gallium selenide (CIGS) as the light absorbing layer in thin film solar cells, was studied in this doctoral work for alternative uses in energy harvesting. This work aims to systemically investigate the prospects of CZTS to be used as hole transport layers and thermoelectric generators. CZTS thin film was successfully fabricated using a versatile approach involving hot-injection synthesis of CZTS nanoparticles ink followed by spin coating and thermal treatment. Results obtained revealed the possibility to fine control CZTS thin film fabrication based on ink concentration and spin. Besides that, thermal treatment temperature was found to affect the film’s overall properties, where an increase in thermal treatment temperature improved the degree of crystallinity and electrical properties. In addition, a phase change going from less stable cubic and wurtzite structures to a more stable tetragonal structure was also observed. Furthermore, CZTS was found to be a good candidate to replace the commonly used organic hole transport layer in perovskite solar cells, with potentials in improving performance and stability. In addition, CZTS also possessed good transport properties to be a potential p-type material in a thermoelectric generator, with the preliminary performance of fabricated CZTS/AZO thermoelectric generator showing a maximum power output of ~350 nW at ~170 KΔT. These findings provide new perspectives for CZTS in energy harvesting applications, despite the struggle in its development as the absorber layer in thin film solar cells. Besides providing a deeper understanding of CZTS and its vast possibilities in energy harvesting applications, promising future research stemming from this work is also limitless, reinventing ways in material studies, in search of alternative applications which may be of benefit.

Two novel materials have been developed: TiO2/poly(dimethylsiloxane) (PDMS) beads as buoyant photocatalyst materials for water remediation, and copper rhodamine‑B silane (Cu‑RBS) as an n ‑type organic/inorganic hybrid for thermoelectric applications. The approach to incorporate TiO2 into low‑density PDMS beads addresses many of the challenges traditionally encountered when creating buoyant photocatalysts, an area which is crucial for wide‑spread remediation of water resources, including natural bodies of water. The performance and reusability of the buoyant photocatalyst materials, demonstrated by using methylene blue as a model degradation target, is strong enough for environmental application. The use of a kinetic model and the introduction of a parameter to allow comparison of buoyant photocatalysts is also included as part of the analysis. The performance of Cu‑RBS was investigated as a low‑temperature thermoelectric material. Clear improvements in the electrical conductivity and Seebeck coefficient are observed for RBS upon coordination to Cu2+. Evidence explaining this improvement is provided by computational analysis and by concentration‑dependent optical absorption and fluorescent emission measurements, all of which indicate that a metal‑to‑ligand charge transfer occurs from Cu2+ to RBS. Although the power factor of Cu‑RBS is low compared to other materials reported in the literature, these results provide a promising approach to increasing both the Seebeck coefficient and electrical conductivity of n‑type small molecule organic systems.