A methodology for the simulation of CPV systems is presented in four distinct sections: input, optics, uncertainty and electrical output. In the input section, existing methods of describing the solar irradiation that is incident at the primary optical element of a CPV system are discussed, the inadequacies of the existing methods are explored and conditions of validity for their use drawn. An improved and spectrally extended model for a variable, spatially resolved solar image is arrived at. The model is used to analyse losses at the primary concentration device stage under varying solar profiles and air masses. A contextual analysis of an example Seattle based CPV system operating with constant solar tracking errors of 0.3-0.4° show a corresponding loss in isolation available to the optical system of 5-20%, respectively. In the optics section, an optical ray trace model is developed specifically for this work. The optical ray trace model is capable of the spectrally resolved ray tracing of all insolation input models discussed above. Plano-convex and Fresnel lenses are designed, investigated and compared using each of the insolation models described in the input section. Common CPV component material samples for the plano-convex and Fresnel lenses are analysed for their spectrally resolved optical properties. The computational expense of high resolution spatial and spectral modelling is addressed by means of a spectrally weighted banding method. The optical properties parameter spectral weighting method can be applied to any arbitrary spectral band. The bands used herein correspond to the active ranges of a typical triple-junction solar cell. Each band shows a different spectral dependency. Banded beam irradiation proportions are shown to change by as much as 10% in absolute terms within the air mass range of 1 to 3. Significant variations in spectrally banded illumination profiles are found with the extended light source insolation model. These banded variations are mostly unaccounted for with the use of approximated insolation models, further compounding the argument for extended light source Sun models in CPV system simulations. In the uncertainty section, the limitations of the manufacturing process are explored. Manufacturing tolerance errors from manufacturer datasheets are presented. These production uncertainties are used in the design of an erroneous plano-convex lens which is then analysed with the optical modelled presented in the optics section and compared to the ideal design specification. A 15% variation in maximum intensity value is found alongside a linear shift in the focal crossover point of approximately 0.2mm, although the optical efficiency of the lens remains the same. Framing manufacture errors are investigated for a square Fresnel lens system resulting in a linear shift of the focal centre of approximately 0.85mm. A process for the calculation of wind loading force on a CPV array is also presented. The process uses real 2 second resolution wind data and highlights the chaotic nature of loading force. A maximum force of 1.4kN was found on an example day for a 3m by 3m by 0.1m cuboid (i.e. CPV array); corresponding to a wind speed of approximately 13m/s, which is well within the typical operating range of a CPV tracking system. In the electrical output section, a spatially resolved solar cell model is identified and used for the investigation of solar cell performance under the inhomogeneous cell illumination profiles produced in the uncertainty section. Significant differences in the maximum power point of the cell IVs are found for the ideal and erroneous system illumination profiles. Approximately, a 15% variation is found in the plano-convex lens example, with a relative difference of 4% attributable to illumination profile distortion, and a 6% variation in the module framing component example. These results further highlight the need for the consideration of production uncertainties in CPV system simulation.

This thesis is a study of the geometric design of solar concentrating collectors. In this work, a numerical optimization methodology was developed and applied to various problems in linear solar concentrator design, in order to examine overall optimization success as well as the effect of various strategies for improving computational efficiency. Optimization is performed with the goal of identifying the concentrator geometry that results in the greatest fraction of incoming solar radiation absorbed at the receiver surface, for a given collector configuration. Surfaces are parametrically represented in two-dimensions, and objective function evaluations are performed using various Monte Carlo ray-tracing techniques. Design optimization is performed using a gradient-based search scheme, with the gradient approximated through finite-difference estimation and updates based on the direction of steepest-descent. The developed geometric optimization methodology was found to perform with mixed success for the given test problems. In general, in every case a significant improvement in performance was achieved over that of the initial design guess, however, in certain cases, the quality of the identified optimal geometry depended on the quality of the initial guess. It was found that, through the use of randomized quasi-Monte Carlo, instead of traditional Monte Carlo, overall computational time to converge is reduced significantly, with times typically reduced by a factor of four to six for problems assuming perfect optics, and by a factor of about 2.5 for problems assuming realistic optical properties. It was concluded that the application of numerical optimization to the design of solar concentrating collectors merits additional research, especially given the improvements possible through quasi-Monte Carlo techniques.

This thesis is a study of the geometric design of solar concentrating collectors. In this work, a numerical optimization methodology was developed and applied to various problems in linear solar concentrator design, in order to examine overall optimization success as well as the effect of various strategies for improving computational efficiency. Optimization is performed with the goal of identifying the concentrator geometry that results in the greatest fraction of incoming solar radiation absorbed at the receiver surface, for a given collector configuration. Surfaces are parametrically represented in two-dimensions, and objective function evaluations are performed using various Monte Carlo ray-tracing techniques. Design optimization is performed using a gradient-based search scheme, with the gradient approximated through finite-difference estimation and updates based on the direction of steepest-descent. The developed geometric optimization methodology was found to perform with mixed success for the given test problems. In general, in every case a significant improvement in performance was achieved over that of the initial design guess, however, in certain cases, the quality of the identified optimal geometry depended on the quality of the initial guess. It was found that, through the use of randomized quasi-Monte Carlo, instead of traditional Monte Carlo, overall computational time to converge is reduced significantly, with times typically reduced by a factor of four to six for problems assuming perfect optics, and by a factor of about 2.5 for problems assuming realistic optical properties. It was concluded that the application of numerical optimization to the design of solar concentrating collectors merits additional research, especially given the improvements possible through quasi-Monte Carlo techniques.

Luminescent solar concentrators (LSC’s) are promising candidates for reducing the cost of solar power generation. Conventional LSC’s are slab waveguides coated or doped with luminescence materials for absorption and guiding of light to the slab edges in order to convert optical energy into electricity via attached photovoltaic (PV) cells. Exploiting the advantages of optical fiber production, a fiber LSC (FLSC) is presented in this thesis, in which the waveguide is a polymeric optical fiber. A hybrid fiber structure is proposed for an efficient two-stage concentration of incident light, first into a small doped core using a cylindrical micro-lens that extends along the fiber, and second to the fiber ends by guiding the fluoresced light from the active dopants. Flexible sheets are assembled with fibers that can be bundled and attached to small-area PV cells. Small dimensions and directional guiding of the fibers allow for approximately one order of magnitude geometrical gain improvement over that of existing flat LSC’s. In addition, the undesired limit of LSC size is eliminated in one direction. Modeling and optimization of an FLSC design is presented using polarization-ray tracing under realistic conditions with solar spectrum radiation and broad-band absorption and emission spectra of fluorescence materials with their inevitable self-absorption effect. Methods and results of fabrication and accurate optical characterization of such FLSC using two off-the-shelf organic dyes and a commercially available polymer, COP, are discussed in detail. Fiber preforms, fabricated under optimized conditions for lowlight transport loss, are thermally iv drawn into sub-millimeter-size fibers. Characterization of several samples with various concentrations of the two dyes shows an optical-to-optical conversion efficiency of 9.1% for a tandem combination of two 2.5-cm-long fibers with the efficiency gradually decreasing to 4.9% with increase in fiber length to 10 cm.

Le développement des systèmes de conversion photovoltaïques ces trente dernières années a permis des améliorations considérables en terme de coût et de performances. A ce jour, les meilleurs rendements de conversion photovoltaïques sont obtenus avec des systèmes à oncentration solaire utilisant des cellules multi-jonctions (MJ) à base de matériaux semi-conducteurs III-V. Dans ce domaine, le meilleur rendement atteint à ce jour est de 46,0 % sous une concentration de 508 soleils avec une cellule à 4 jonctions issu du partenariat Soitec/Fraunhofer ISE/CEA. Cette cellule MJ est composée d’une cellule tandem accordée sur GaAs assemblée par collage moléculaire à une autre cellule tandem accordée sur InP. Bien que le rendement atteint soit élevé, les performances de la cellule sont limitées sous fortes concentrations à cause de ce collage moléculaire. Dans le domaine des fortes concentrations, le record est actuellement détenu par la société américaine Solar Junction avec un rendement de 44,0 % mesuré sur une cellule triple jonction monolithique en GaInP/GaAs/GaInNAs de 0,3 cm² pour un taux de concentration de 942 soleils (irradiance directe de 942 kW/m²). Une seconde cellule a atteint un rendement performant à une irradiance directe supérieure à 1 MW/m², il s’agit d’une cellule tandem en GaInP/GaAs de l’IES-UPM qui a atteint 32,6 % sous une concentration de 1026 soleils.Dans le contexte précédent, les travaux présentés dans ce manuscrit visent à l’évaluation d’une nouvelle filière dans le domaine du CPV à base de semi-conducteurs III-V : la filière antimoniure (III-Sb). Les cellules que nous avons étudiées dans le cadre de cette thèse sont à base de GaSb et de l’alliage AlxGa1-xAsySb1-y, fabriquées de façon monolithique par MBE (Molecular Beam Epitaxy) sur substrat GaSb. Ce type de cellules, du fait de la très bonne complémentarité des gaps des matériaux, constitue une alternative crédible et originale aux cellules existantes pour une utilisation sous flux solaire fortement concentré.Le travail à réaliser dans le cadre de cette thèse porte sur :- La caractérisation électrique et optique des alliages quaternaires utilisés.- La conception et le design des cellules.- La réalisation et la mise au point de toutes les étapes technologiques nécessaires à la conception des cellules (photolithographie UV, gravure, métallisation, …).- La caractérisation électrique et optique des cellules fabriquées (I(V), TLM, réponse spectrale, …).- La caractérisation des cellules sous flux solaire (fortement) concentré.Ce travail a été cofinancé par l’Université de Montpellier et le LabEx SOLSTICE. / The development of photovoltaic conversion systems these past thirty years led to considerable improvements in terms of cost and performances. The best conversion efficiencies are currently obtained with solar concentration systems associated with multi-junction solar cells (MJSC) made of III-V materials. In this field, the record efficiency is of 46.0% under a 508-sun solar concentration with a 4-junction cell from Soitec/Fraunhofer ISE/CEA. This MJSC is composed of a tandem cell lattice-matched to GaAs wafer bonded to another tandem cell lattice-matched to InP. Although it reached high conversion efficiency, its performances are limited under solar concentration because of the wafer bonding. In the field of high solar concentrations, the record is held by Solar Junction with a monolithic triple junction GaInP/GaAs/GaInNAs cell of 0.3 cm² that reached an efficiency of 44.0% under 942 suns (direct irradiance of 942 kW/m²). Another high solar concentration efficiency record worth mentioning is held by IES-UPM with a tandem solar cell (GaInP/GaAs) that reached an efficiency of 32.6% under a concentration of 1026 suns.In this context, the work presented in this manuscript aims to evaluate the potential of a new family of III-V materials for high solar concentration applications: antimonide-based materials (III-Sb). The studied cells in this thesis are made out of GaSb and the quaternary AlxGa1-xAsySb1-y, monolithically grown by MBE (Molecular Beam Epitaxy) on a GaSb substrate. These materials, thanks to the large range of available band-gaps, represent an original and well-founded alternative to existing solar cells for high solar concentration applications.The work achieved in this thesis covers:- The electrical and optical characterization of the quaternary materials used.- The conception and designing of the cells.- The production and tuning of every technological steps in order to fabricate our solar cells (UV photolithography, etching, metal deposition,…).- The electrical and optical characterization of our fabricated solar cells (I(V), TLM, spectral response,…).- The characterization under (high) solar concentration of our cells.This work was cofounded by the University of Montpellier and the LabEx SOLSTICE.

Após a reunião de Kyoto ficou estabelecido o sistema de \"crédito carbono\" no qual as indústrias que reduzissem a emissão de gás carbônico para o ambiente aufeririam algumas vantagens. Neste sentido já há uma procura por parte de algumas empresas em reduzir esta emissão. Na maioria dos casos esta emissão é reduzida por meio da absorção do CO2 através de uma base, por exemplo, soda, amônia, cal, aminas, entre outras. O caso da amônia e da soda é interessante para empresas que possuem outros efluentes com estas bases em concentrações bem baixas, resultando assim soluções bem diluídas dos sais correspondentes. Soluções muito diluídas ou são descartadas no meio ambiente, que atualmente é proibido, ou são concentradas. A concentração, dessas soluções, usando vapor como meio de aquecimento torna-se um contra-senso por exigir a emissão de CO2 decorrente da queima de óleo combustível em caldeiras. Técnicas bem mais compatíveis com a preservação ambiental serão bem vindas daqui por diante, principalmente aquelas que não emitem CO2. Observando este fato este trabalho visa desenvolver um evaporador com promotor de película, em escala de laboratório para concentrar soluções diluídas, empregando energia solar como meio de aquecimento. O procedimento proposto não emite CO2, sendo mais compatível com a preservação ambiental. O equipamento construído consta de: coletor solar tipo placa plana com inclinação ajustável, promotor de película (aderido ao coletor),distribuidor de líquido, coletor de concentrado e acessórios. Foram estudadas as influências das variáveis: inclinação do coletor, vazão de alimentação e condições meteorológicas, na taxa de evaporação. As condições meteorológicas não podem ser controladas, mas foram constantemente monitoradas. Obtiveram-se maiores eficiências, quando a inclinação do coletor foi ajustada mensalmente, com valores até 36,4% maiores do que quando o coletor permanece fixo. / The system of Carbon Credits established by the 1997 Kyoto Protocol benefits companies that reduce their emissions of carbon into the environment with some advantages. Since the Protocol was signed, many companies have sought new ways to reduce their emissions. In most cases, these emissions are reduced through CO2 absorption by a base, e.g., soda, ammonia, lime and amines, among others. Ammonia and soda are interesting bases for companies that produce other effluents containing these products in much lower concentrations, resulting in highly diluted solutions of the corresponding salts. Highly diluted solutions are either discharged into the environment, which is forbidden today, or they are concentrated. Concentrating these solutions using vapor, as a means of heating is unfeasible since that would involve the emission of CO2 from burning oil in boilers. Therefore, from now on, attention will focus increasingly on more environmentally friendly techniques, especially techniques that do not cause CO2 emissions. A solar energy powered falling film evaporator with film promoter was developed for concentrating diluted solutions (industrial effluents). The procedure proposed here does not emit CO2, making it a viable alternative to the method of concentrating solutions. This novel device consists of the following components: a flat plate solar collector with adjustable inclination, a film promoter (adhering to the collector), a liquid distributor, a concentratecollector, and accessories. The evaporation rate of the device was found to be affected both by the inclination of the collector and by the feed flow. The meteorological variables cannot be controlled, but were monitored constantly to ascertain the behavior of the equipment in response to the variations occurring throughout the day. ) Higher efficiencies were attained when the inclination of the collector was adjusted monthly, showing up to 36.4% higher values than when the collector remained in a fixed position.

Após a reunião de Kyoto ficou estabelecido o sistema de \"crédito carbono\" no qual as indústrias que reduzissem a emissão de gás carbônico para o ambiente aufeririam algumas vantagens. Neste sentido já há uma procura por parte de algumas empresas em reduzir esta emissão. Na maioria dos casos esta emissão é reduzida por meio da absorção do CO2 através de uma base, por exemplo, soda, amônia, cal, aminas, entre outras. O caso da amônia e da soda é interessante para empresas que possuem outros efluentes com estas bases em concentrações bem baixas, resultando assim soluções bem diluídas dos sais correspondentes. Soluções muito diluídas ou são descartadas no meio ambiente, que atualmente é proibido, ou são concentradas. A concentração, dessas soluções, usando vapor como meio de aquecimento torna-se um contra-senso por exigir a emissão de CO2 decorrente da queima de óleo combustível em caldeiras. Técnicas bem mais compatíveis com a preservação ambiental serão bem vindas daqui por diante, principalmente aquelas que não emitem CO2. Observando este fato este trabalho visa desenvolver um evaporador com promotor de película, em escala de laboratório para concentrar soluções diluídas, empregando energia solar como meio de aquecimento. O procedimento proposto não emite CO2, sendo mais compatível com a preservação ambiental. O equipamento construído consta de: coletor solar tipo placa plana com inclinação ajustável, promotor de película (aderido ao coletor),distribuidor de líquido, coletor de concentrado e acessórios. Foram estudadas as influências das variáveis: inclinação do coletor, vazão de alimentação e condições meteorológicas, na taxa de evaporação. As condições meteorológicas não podem ser controladas, mas foram constantemente monitoradas. Obtiveram-se maiores eficiências, quando a inclinação do coletor foi ajustada mensalmente, com valores até 36,4% maiores do que quando o coletor permanece fixo. / The system of Carbon Credits established by the 1997 Kyoto Protocol benefits companies that reduce their emissions of carbon into the environment with some advantages. Since the Protocol was signed, many companies have sought new ways to reduce their emissions. In most cases, these emissions are reduced through CO2 absorption by a base, e.g., soda, ammonia, lime and amines, among others. Ammonia and soda are interesting bases for companies that produce other effluents containing these products in much lower concentrations, resulting in highly diluted solutions of the corresponding salts. Highly diluted solutions are either discharged into the environment, which is forbidden today, or they are concentrated. Concentrating these solutions using vapor, as a means of heating is unfeasible since that would involve the emission of CO2 from burning oil in boilers. Therefore, from now on, attention will focus increasingly on more environmentally friendly techniques, especially techniques that do not cause CO2 emissions. A solar energy powered falling film evaporator with film promoter was developed for concentrating diluted solutions (industrial effluents). The procedure proposed here does not emit CO2, making it a viable alternative to the method of concentrating solutions. This novel device consists of the following components: a flat plate solar collector with adjustable inclination, a film promoter (adhering to the collector), a liquid distributor, a concentratecollector, and accessories. The evaporation rate of the device was found to be affected both by the inclination of the collector and by the feed flow. The meteorological variables cannot be controlled, but were monitored constantly to ascertain the behavior of the equipment in response to the variations occurring throughout the day. ) Higher efficiencies were attained when the inclination of the collector was adjusted monthly, showing up to 36.4% higher values than when the collector remained in a fixed position.

This thesis presents the achievements pursued during the doctoral course. The work was carried out in the context of the project ERiCSol (Energia RInnovabile e Combustili SOLari), as part of the University of Trento strategic plan for the years 2017-2021. The project was conceived to establish an interdepartmental area to promote the challenge of developing scientific research and technological innovation to increase the competitiveness of Trento at national and international level in the areas of energy and environment. Among all the goals of the project, this work dedicates special attention to 1) development of novel materials for solar photocatalytic reactions and 2) use of renewable energy to push forward applications in water remediation. To accomplish these goals, the research brings a full collection of experimental activities regarding the employment of solar concentration for the environment industry and therefore this document is organized in 9 chapters. In chapter 1, it is presented the introduction outlining the overview of the environment industry, the employment of solar light as energy source and the general and specific objectives. Chapter 2 presents a literature review regarding the last 30 years of applications correlating the use of solar light towards wastewater purification. The chapter reviews the engineering features of solar collectors, photocatalyst materials employed and the panorama of the pollutants investigated up to the present date in solar photocatalysis, presenting comparisons between models and real wastewater approaches. Chapter 3 details the experimental techniques and characterizations employed to sustain the investigation proposed in the thesis. The first part of the chapter explains the features of parabolic dish solar concentrator designed and manufactured by the IdEA group at the physics department of the university of Trento. After, it is presented the pulsed laser deposition, a thin films fabrication technique employed to produce the photocatalysts used on water purification experiments. The second part of the chapter presents the description of the characterization techniques used to reveal the fabricated photocatalyst materials properties. Based on the review on the fundamentals of solar photocatalysis and the experimental techniques, chapters 4 and 5 present a discussion in the field of novel photocatalytic materials capable to operate under concentrated sunlight irradiation. Chapter 4 in special presents the investigation regarding the fabrication of tungsten trioxide (WO3) thin film coatings, bringing the novelty of using pulsed laser deposition as the fabrication method and the evaluation of this material in photocatalysis for the degradation of methylene blue dye model pollutant. Chapter 5 instead, presents the development on Zinc Oxide (ZnO) nanoparticles, bringing an innovative point of view on a “green-synthesis” approach and the material immobilization in film for heterogeneous photocatalysis routes. Chapters 6 and 7 discuss solar photocatalysis aiming to shift applications from model pollutants to real wastewater remediation conditions. Important comparisons are performed and discussed regarding the advantages and existing drawbacks. To fulfill this purpose, chapter 6 presents an application case of solar photocatalysis to the degradation of a surfactant-rich industrial wastewater whereas chapter 7 presents the approach focused on the remediation of organic lead contaminants present on a local water well site in the city of Trento. The last experimental approach of concentrated solar light is presented on chapter 8, dedicated to the application of concentrated sunlight towards waste biomass valorization. Conversely to the application on water previously described, this chapter presents the activity on designing, fabricating and coupling a hydrothermal reactor with concentrated sunlight using it as the driving force to promote degradation of grape seeds evolving into hydrochars with possible valorization of the carbonized material. Lastly, chapter 9 presents the conclusions and suggestions, this item expresses the final considerations on the results of the experimental investigations, advantages and limitations observed, and suggests possible actions for future works.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This work deals with the analysis applied to the main methodologies found in literature for estimating the properties related to the physical phenomena in photovoltaic devices (parametrization), as well as the most important mathematical models used in the calculation of operating electrical characteristics of these devices (characterization). These devices are related to the mono and multi-junction technologies, when they are exposed to a condition where the temperature and solar radiation vary. Therefore, four parametrization methods were shown, including three analytical, and five models of electrical characterization, where two of them are specifically for multi-junction devices. Thus, several case studies were proposed which defined different situations for comparing the performance of the methods evaluated. In this way, the procedures that best fit to each type of photovoltaic technology were identified. Finally, according to the results obtained in the parameterization, the method based on the Generalized Reduced Gradient (GRG) nonlinear algorithm showed greater accuracy for all case studies and for all photovoltaic devices. As for the characterization, the main advantages and disadvantages of all models were determined, highlighting Domínguez, et al. (2010) model, due to the highest robustness and wide application range. / Esta dissertação apresenta uma análise aplicada às principais metodologias encontradas na literatura que permitem determinar as propriedades físicas relativas aos fenômenos que ocorrem nos dispositivos fotovoltaicos (etapa de parametrização), assim como dos modelos matemáticos de maior importância utilizados no cálculo das características elétricas operacionais destes dispositivos (etapa de caraterização). Tais dispositivos referem-se às tecnologias mono e multi junção quando submetidos à variações de temperatura e radiação solar. Portanto, foram apresentados quatro métodos de parametrização, entre eles três analíticos e cinco modelos de caracterização elétrica, sendo dois especificamente para dispositivos multi junção. Assim, estabeleceram-se vários estudos de caso para os quais foram definidas diferentes situações que permitiram comparar o desempenho de cada um dos métodos avaliados. Em consequência, foram identificados os procedimentos que melhor se ajustaram a cada tipo de tecnologia fotovoltaica. Dessa forma, de acordo com os resultados obtidos na parametrização, a metodologia baseada na aplicação do algoritmo de Gradiente Reduzido Generalizado (GRG) não linear, demonstrou maior exatidão para todos os estudos de caso e para todos os dispositivos fotovoltaicos. Já para a caraterização, foram determinadas as principais vantagens e desvantagens entre os modelos aplicados, destacando o modelo de Domínguez, et al. (2010), que apresentou maior robustez e ampla faixa de aplicação. / Mestre em Engenharia Mecânica

La limite théorique de rendement des cellules photovoltaïques simple-jonction est de l’ordre de 33% d’après le modèle de Shockley-Queisser, ce qui reste éloigné de la limite de Carnot, prédisant une limite maximale de conversion énergie solaire → électricité de 93%. L’écart important entre ces deux limites découle des pertes intrinsèques, essentiellement liées à la conversion inefficace du spectre solaire et à la disparité entre les angles solides d’absorption et d’émission. Pour surmonter ces pertes et se rapprocher de la limite de Carnot, trois stratégies sont envisagées dans cette thèse : les cellules multi-jonction àconcentration, la combinaison de la concentration et de la restriction angulaire et les systèmes hybrides PV/CSP. Chacune de ces stratégies est limitée par des mécanismes qui dégradent leur performance.L’objectif de cette thèse est donc de comprendre dans quelle mesure les différents mécanismes limitants sont susceptibles d’affecter les performances des différentes stratégies étudiées, et d’optimiser l’architecture des cellules dans le but d’accroitre leur efficacité de conversion. Dans ce but, un modèle détaillé de cellule solaire tenant compte des principaux mécanismes limitant a été développé. Un outil d’optimisation par algorithme génétique a également été mis au point, afin d’explorer l’espace des différents paramètres étudiés pour identifier les conditions d’opération optimales. Nous démontrons l’importance majeure que revêt l’adaptation des propriétés optoélectroniques des matériaux utilisés aux conditions opératoires, que ce soit dans le cas des cellules solaires à concentration endurant des pertes résistives significatives, ou encore dans le cas de cellules solaires fonctionnant à des niveaux de températures très supérieurs à l’ambiante. Enfin, nous avons déterminé l’effet des principaux facteurs limitant que constituent les pertes résistives et les recombinaisons non-radiatives sur les cellules solairessimultanément soumises au flux solaire concentré et à la restriction angulaire du rayonnement émis. / The maximum efficiency limit attainable with a single-junction PV cell is ~ 33% according to the detailed balance formalism (also known as Shockley-Queisser model), which remains far from the Carnot limit, predicting a solar to electricity efficiency upper value of 93%. The large gap between both limits is due to intrinsic loss mechanisms, including the inefficient conversion of the solar spectrum and the large discrepancy between the solid angles of absorption and emission. To overcome these losses and get closer to the Carnot limit, three different strategies are considered in this thesis: concentrated multi-junction solarcells, the combination of solar concentration and angular confinement, and hybrid PV/CSP systems. Each strategy is inherently limited by several loss mechanisms that degrade their performances. The objective of this thesis is, hence, to better understand the extent to which these strategies are likely to be penalized by these losses, and to tailor the cell properties toward maximizing their efficiencies. To address these questions, a detailed-balance model of PV cell accounting for the main loss mechanisms was developed. A genetic-algorithm optimization tool was also implemented, aiming at exploring the parameter space and identifying the optimal operation conditions. We demonstrate the uttermost importance of tailoring the electronic properties of the materials used with both multi-junction solar cells undergoing significant series resistance losses, and PV cells operating at temperature levels exceeding ambient temperature. We also investigate the extent to which series resistances losses and non-radiative recombination are likely to affect the ability of PV cells simultaneously submitted to concentrated sunlight and angular restriction of the light emitted by band-to-band recombination.