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[en] We show how Cooper-pair-assisted transport, which describes the stimulated transport of electrons in the presence of Cooper-pairs, can be engineered and controlled with cold atoms, in regimes that are difficult to access for condensed matter systems. Our model is a channel connecting two cold atomic gases, and the mechanism to generate such a transport relies on the coupling of the channel to a molecular BEC, with diatomic molecules of fermionic atoms. Our results are obtained using a Floquet–Redfield master equation that accounts for an exact treatment of the interaction between atoms in the channel. We explore, in particular, the impact of the coupling to the BEC and the interaction between atoms in the junction on its transport properties, revealing non-trivial dependence of the produced particle current. We also study the effects of finite temperatures of the reservoirs and the robustness of the current against additional dissipation acting on the junction. Our work is experimentally relevant and has potential applications to dissipation engineering of transport with cold atoms, studies of thermoelectric effects, quantum heat engines, or Floquet Majorana fermions. (paper)
[en] After a synthesis of the 4. quarter 2020 news and a focus on the implementation of the French solar energy development plan 'PlaceAuSoleil', this publication presents in a series of graphs the situation of photovoltaic energy development in France and in the whole world: evolution of the world's photovoltaic park (new and cumulated capacities), world comparison of production costs of new power generation capacities, photovoltaic power generation in France (photovoltaic share in the French power consumption, new connected capacities per surface size and for self-consumption, evolution of connected capacities rate, self-consumption market trend, residential market analysis and feed-in tariffs per surface size, pending projects, evolution of feed-in tariffs in continental France, extra public burdens induced by new connections with respect to surface size.
[en] After a synthesis of the 3. quarter 2020 news and a focus on the implementation of the French solar energy development plan 'PlaceAuSoleil', this publication presents in a series of graphs the situation of photovoltaic energy development in France and in the whole world: evolution of the world's photovoltaic park (new and cumulated capacities), world comparison of production costs of new power generation capacities, photovoltaic power generation in France (photovoltaic share in the French power consumption, new connected capacities per surface size and for self-consumption, evolution of connected capacities rate, self-consumption market trend, residential market analysis and feed-in tariffs per surface size, pending projects, evolution of feed-in tariffs in continental France, extra public burdens induced by new connections with respect to surface size.
[en] The author reports a study which aimed at developing a photovoltaic generator with concentration by coupling of an existing linear concentrator based on segmented mirrors with photovoltaic cells specifically designed to operate under flow concentration. The author first briefly recalls basic principles of the photovoltaic effect, and the development of conventional analytic models for PN junctions. He analyses the various loss factors which limits the energy efficiency. He describes the structure of N+PP+ cells which allows better performance than the NP structure to be obtained. In the next part, the author describes cells which are foreseen to be operated under concentration, and reports their experimental study (electrical, optical and thermal characterisation). Based on the obtained results, the author addresses the optimisation of the electrical and thermal design of the generator, and reports an experimental study of the generator associated with the linear concentrator. The last part reports a comparative economic study between the studied concentration-based system, and systems without concentration
[fr]L'objectif du travail est de realiser un generateur photovoltaique a concentration par couplage d'un concentrateur lineaire a miroirs segmentes existant avec des cellules photovoltaiques specialement concues pour travailler sous concentration de flux. L'optimisation d'un tel dispositif doit commencer par la connaissance du comportement de la photopile sous concentration: etude des parametres electriques et thermoelectriques en relation avec la densite du flux lumineux concentre (et donc, de la temperature locale). L'experimentation est faite sur 80 photopiles au silicium, adaptees a fonctionner sous concentration moyenne (∼20) et mises au point par la RTC (Radio Technique Compelec - CAEN) en collaboration avec le LEP (Laboratoires d'Electronique et de Physique Appliquee LIMEIL-BREVANNES). Ces photopiles servent egalement a realiser le generateur destine a fonctionner sur le concentrateur existant. Dans un premier chapitre, nous rappelons brievement les principes de base de l'effet photovoltaique et developpons les modeles traditionnels analytiques pour les jonctions PN. Nous analysons les divers facteurs de perte qui limitent le rendement energetique. Nous decrivons ensuite la structure des photopiles N+PP+ permettant d'obtenir des performances meilleures que celle de la structure NP. Le deuxieme chapitre est consacre a la description des cellules prevues pour fonctionner sous concentration et a leur etude experimentale (caracterisation electrique, optique et thermique). Au vu des resultats precedents, le troisieme chapitre porte sur l'optimisation de la conception electrique et thermique du generateur. Il est suivi d'une etude experimentale du generateur associe au concentrateur lineaire. Le quatrieme chapitre est consacre a une etude economique comparative entre le systeme a concentration etudie par rapport aux systemes sans concentration. (auteur)
[en] Silicon nanowires, whose thermal conductivity is strongly reduced with respect to that of the bulk silicon, are very promising for high-efficient thermoelectric conversion. This work focuses on the development of a technique for the fabrication of thermoelectric generators which are based on vertical silicon nanowire forests, achieved through a metal-assisted chemical etch. As heavily doped nanowires are essential in thermoelectric applications, this chemical process has been applied both on lightly and on highly doped (> 1019 cm−3) silicon substrates. A comparison of the results shows that the etch behaves in a completely distinct way when applied to the differently doped substrates. The results of this comparison and a preliminary insight into the diverse behavior occurred are reported. The different initial nucleation of silver, which determines the hole injection, essential to the etching of silicon, seems to be the key point of this different behavior.
[en] Ternary Heusler compounds form a numerous class of intermetallics, which include two families with general compositions ABC and AB2C, usually referred to as half- and full-Heusler compounds, respectively. Given their tunable electronic properties, made possible by adjusting the chemical composition, these materials are currently considered for the possible use in sustainable technologies such as solar energy and thermoelectric conversion. According to theoretical predictions, Sb substitution in the TiFe2Sn full-Heusler compound is thought to yield band structure modifications that should enhance the thermoelectric power factor. In this work, we tested the phase stability and the structural and microstructural properties of such heavily doped compounds. We synthesized polycrystalline TiFe2Sn1−xSbx samples, with x = 0, 0.1, 0.2 and 1.0 by arc melting, followed by an annealing treatment. The structural characterization, performed by x-ray powder diffraction and microscopy analyses, confirmed the formation of the pseudo-ternary Heusler structure (cF16, Fm-3m, prototype: MnCu2Al) in all samples, with only few percent amounts of secondary phases and only slight deviations from nominal stoichiometry. With increasing Sb substitution, we found a steady decrease in the lattice parameter, confirming that the replacement takes place at the Sn site. Quite unusually, the as-cast samples exhibited a higher lattice contraction than the annealed ones. The fully substituted x = 1.0 compound, again adopting the MnCu2Al structure, does not form as stoichiometric phase and turned out to be strongly Fe deficient. The physical behavior at room temperature indicated that annealing with increasing temperature is beneficial for electrical and thermoelectrical transport. Moreover, we measured a slight improvement in electrical and thermoelectrical properties in the x = 0.1 sample and a suppression in the x = 0.2 sample, as compared to the undoped x = 0 sample.
[en] Bismuth telluride (Bi2Te3) has garnered significant interest in thermoelectric applications and three-dimensional topological insulators due to its unique electronic, transport, and thermal properties. Bi2Te3 and Sb2Te3 chalcogenide compounds have the same crystal structure. While Sb2Te3 has been shown to be a prototypical phase change memory (PCM) compound along the pseudobinary tie-line of Ge-Sb-Te alloys, whether Bi2Te3 can also exhibit PCM functionality is still not well established. In this work, a systematic study on the structural, dynamical, and electronic properties of amorphous Bi2Te3 during the quenching process has been performed by using ab initio molecular dynamics simulations. Pair correlation function, coordination number, bond-angle distribution functions, and a novel atomistic cluster alignment method are used to explore the structural characteristics of Bi2Te3 as a function of temperature. Our study shows that there are many distorted octahedral clusters in amorphous Bi2Te3. In comparison with the local structures in Sb2Te3, we found that the degree of distortion of the octahedrons in the Bi2Te3 system is smaller than that in Sb2Te3 system. Moreover, the changes in the dynamical properties of Bi2Te3 from liquid to glassy state are also explored. The approximate range of liquid-to-glass transition temperature is determined to be between 673 and 723 K. The electronic properties of Bi2Te3 and Sb2Te3 are also analysed by density-of-states and Bader charge calculations, both of them in glass state are semiconductors. Our studies provide useful insights into the local structure and dynamical properties of Bi2Te3 at the atomistic level during the fast cooling process, and suggest that the compound can be a candidate for PCM materials. (paper)
[en] A first report presents an overview of the context of ground-based photovoltaic power plants: accelerating growth, development perspectives for 2020, evolution of the regulatory framework, calls for tenders for ground-based plants in France and in Germany, market actors. It describes and comments the technological aspects of the photovoltaic module which is at the heart of the system: fundamental differences between two fabrication processes, technological differences (crystalline silicon, thin layer technologies), evolution of efficiency per technology, energy performance, paths to be explored to keep on decreasing the module price. It reports an analysis of the investment in a ground-based plant of 10 MW in 2016 with a 50/50 distribution among module and BOS (Balance of System), and finally reports a modelling study of the LCOE (Levelized cost of energy). A second document proposes a more detailed presentation of the various technologies (efficiencies and scientific and technological locks, bibliometric study, actors), of the evolution of electricity cost depending on the technologies (LCOE analysis, parameter impact study and sensitivity study), and an analysis of industrial investments.
[fr]A la demande du groupe programmatique 4 'Energies solaires' (GP4) de l'Alliance nationale de coordination de la recherche pour l'energie (Ancre), le CVT a realise une etude visant a evaluer 'Le potentiel technologique et economique des filieres photovoltaiques a haut rendement' au travers de quatre axes majeurs: - L'analyse des avancees technologiques en cours aux sens de la R et D, avec une etude bibliometrique sur le depot de brevets et de publications; - L'identification des verrous scientifiques et technologiques au developpement; - L'etude des investissements annonces dans de nouvelles capacites industrielles; - La prevision de l'evolution du prix de l'electricite delivree selon les technologies. Ce rapport adresse le dernier sujet; le cout moyenne de l'electricite appele LCOE. Dans le cas du photovoltaique, pour le calculer, il est necessaire de definir trois parametres fondamentaux qui sont: - le type d'installation (residentiel, industriel, centrale au sol), - le lieu d'installation precis (coordonnees geographiques), - l'annee et le pays d'investissement. Ainsi la centrale au sol de quelques MWc raccordee au reseau de distribution, sans contrainte particuliere pour l'injection de l'electricite a ete prise comme installation de reference, localisee en France, Allemagne, Italie et Californie. Pour realiser ce travail, des experts academiques des filieres photovoltaiques ont ete consultes ainsi que des acteurs industriels des centrales au sol francais et etrangers comme des equipementiers: fabricants de modules, onduleurs, support-structure, trackers, des installateurs, des investisseurs et des exploitants. L'etude a permis d'adresser les questions suivantes: - Quels couts d'investissement et de production de l'electricite en 2016? - Quelles evolutions du cout de production de l'electricite photovoltaique peut-on attendre? - Quel est le potentiel de baisse de cout inherente a chaque technologie? - Quelle est l'importance des differentes composantes du LCOE? - Quel impact de la localisation (niveau d'ensoleillement et politiques locales)?
[en] Molecular beam epitaxy was applied to evaporate a set of Au/ZnTe:I/CdTe:I/GaAs/In heterostructures. The resulted heterostructures were examined for photovoltaic energy conversion application. Electrical characteristics were studied for understanding the relevant electrical transport mechanisms. The current–voltage (I–V) characteristics were checked under dark and light conditions. Ideality factor indicates the recombination mechanisms in the designed device; its value equals (3.22). Under various light intensities (1–140 mW cm−2), the I–V curves are affected highly by reverse voltage bias. The open-circuit voltage increases exponentially with the illumination and its values of this device increased with increasing light intensity (L), where 55 mV at 1 mW cm−2 and 465 mV at 140 mW cm−2. Electrical as well as power related parameters of the designed device were interpreted. Photosensitivity and Responsitivity of the studied device showed a high photoresponse under different light intensities. Au/ZnTe:I/CdTe:I/GaAs/In heterostructures is a promising material for photosensor and optoelectronic applications.
[en] Copper Zinc Tin Sulfide (CZTS) is a growing semiconductor chalcogenide that has the potential to act as an alternative nontoxic absorber for commercial silicon-based devices in the sustainable photovoltaic conversion of solar energy in the near future. A debut attempt was made to economically fabricate this earth-abundant solar absorber thin film through indigenously designed cost-effective nebulizer assisted chemical spray pyrolysis technique without high-temperature annealing. The deposition was carried out at different spray volumes to modify the thickness of the absorber material directly on a bare soda-lime glass substrate and effect of CZTS film thickness on its structural, morphological, optical and electrical properties were studied by using appropriate characterization techniques. The film with a thickness of 740 nm for a precursor spray volume of 12 ml resulted in CZTS film with better energy conversion characteristics. (paper)