The aim of the project is to provide low-cost and high efficiency tandem cells grown on crystalline silicon (c-Si) substrates, with merging both the monocristalline Si approach with the high-efficiency monocristalline multijunction approach based on III-V materials. These CPV cells will be used under natural lighting and under low light concentrators (100 suns) developed by IRDEP-CNRS, and benchmarked under medium concentration by Heliotrop sas. The PV cells efficiency is one of the most important parameters for the final cost of electricity, since it impacts directly the ratio between produced energy and production cost. With 22% efficiency modules based on c-Si, the technology seems to reach its limits. To increase further the efficiency of c-Si cells and modules, going to multijunction devices (association of two different absorbing layers in the same cell) seems to be the obvious choice. While many projects tend to focus on all silicon technology, best high bandgap cells are yet based on III-V compounds. This project proposes to demonstrate the proof-of-concept for a monolithic integration of high efficiency multijunction CPV device on a low cost monocristalline silicon substrate upon which a III-V lattice-matched material will be grown using molecular beam Epitaxy (MBE). This Lattice-Matched heterostructure with its very low structural defect densities (Dislocations, AntiPhase Domains, point defects) will be capable of sustaining III-V high performing PV devices onto silicon with long life-time. This novel route overcomes the problems of high cost substrates (as compared to Ge or III-V substrates used currently for this kind of CPV), the killer structural defect formation and reliability issues of lattice mismatched systems (metamorphic approach) and the low reliability and low lifetime of hybrid techniques (such as wafer bonding). The integration of photovoltaic functions onto a single silicon substrate will also achieve a reduction in the use of III-V based semiconducting materials in high-efficiency multijunction CPVs. The two main scientific and technologic objectives of the project are : 1) The achievement of GaAsPN (1.7 eV) single cell on Si (with a 15% efficiency under low concentration, i.e. 100 sun). 2) The demonstration of a high efficiency and low cost multi-junction solar cell: GaAsPN pn cell at 1.7 eV on Si pn cell at 1.1 eV (25% efficiency under low concentration, i.e. 100 sun, as a first step towards very high-efficiencies >30%) Lattice-matched layers and slightly tilted substrates are used to overcome the two main difficulties faced by the growth of III-V materials on silicon substrates: misfit dislocations and antiphase lattice defects, in order to obtain defect-free III-V materials and to get large minority carrier diffusion lengths for the PV applications. The PV devices will consist in high efficiency tandem cells III-V/Si double-pn-junctions separated with a Buried Tunnel Junction. The final structure will include a first bottom Si pn (1.1eV low gap) grown on the Si substrate, then a thin GaP layers is grown by MBE to prevent structural defects formation, a top cell GaAsPN pn (1.7eV large gap) junction is then grown on top of it. The project relies on a high quality consortium which brings together six french partners, and an associated European partner, with high, established competence and complementary methodology and expertise in their fields and leading appropriate workpackages: FOTON (growth of III-V materials), INL (Si-based PV technology), CEMES-CNRS (structural characterizations), IRDEP-CNRS (research in PV development), EDF R&D (a European leader in the Energy sector), HELIOTROP (French manufacturer of high concentration photovoltaic modules (HCPV)) and AALTO (a Finnish associated academic partner specialised in point defects analysis). The partners are active in European research consortia and in networks of excellence and they drive many projects on the national and international level.

Particle and radiation beams are commonly used in our daily life. For example, electrons are accelerated and deflected in the cathode tube of television or computer screens. Higher-energy electrons slowing down in targets with high atomic number produce X rays by the so-called Bremsstrahlung process. Such X rays are routinely used for radiography and non destructive material or body inspection, for example to check human bodies (to visualize tumour cells, dental caries and osseous fractures) or to increase the safety of travellers by inspecting their luggage. Ionizing radiations are efficiently used in radiation therapy to cure cancers by damaging the DNA of cells, for which most of the radiation effect is through free radicals, notably hydroxyl radicals, which result from the ionization of water. To cure cancer, it is also very important to have detailed localisation of tumour cells and detailed knowledge of surrounding regions crossed by the ionizing radiation which will irradiate the patients. These data are crucial for optimizing treatment planning since the dose deposition depends sensitively on the constitution of the body. Such images are also performed with X ray beams or using radio-isotopes produced with particle beams. From the fundamental point of view, the development of ultra short bunches of energetic particles and X ray photons is of crucial importance in biology, chemistry, and solid state physics, where these beams could be used to diagnose the electronic, atomic or molecular dynamics with unprecedented, simultaneous time and space resolution. On the other hand, achievement of high X ray intensities will extend nonlinear optics to the X ray spectral range and permit the creation of new states of matter such as dense plasmas of astrophysical or geophysical interests. Intense and energetic photon and neutron beams are also important developments that can benefit to the nuclear physicists community. It has been demonstrated in the last ten years that short pulse delivered by compact lasers can generate these various particle sources[1]. These bright sources of electrons, protons, gamma radiation and neutrons are now more and more reproducible and particularly their parameters (energy, brightness, emittance, …) have been found to be adjustable. The LOA has played with other important laboratories in Europe, in Asia and in America a major rule in the development of these innovative sources of particle and radiation. The excellent knowledge of the Romanian groups in nuclear physics and in particle and radiation detectors added to the knowledge of the LOA groups on these sources development will give a new impulse in these research areas, it will contribute through this jointed and collaborative ANR to build up a strong exchange of knowledge, to train nuclear physicists from Romania to use and to master the experimental and complex apparatus around nice and performance laser plasma interaction platform recently upgraded. The work that will be covered and achieved during this three years contract will be of course of major relevance to prepare the ELI-NP (Extreme Light Infrasctructure – Nuclear Physics) Romanian project.

La théorie économique récente s'attache à analyser plus précisément l'hétérogénéité des préférences et la genèse des goûts. En effet, il a souvent été reproché aux économistes d'avoir une vue étroite sur les facteurs déterminant les choix des individus (rationalité de l'homo oeconomicus), et notamment, de ne pas suffisamment s'intéresser à leurs dimensions subjectives. Et empiriquement, il est illusoire de vouloir expliquer la distribution de certaines variables (patrimoine, revenu, consommation,...) sans prendre en compte cette hétérogénéité. - Pour expliquer les comportements humains, la microéconomie du consommateur, outre la distribution des revenus et la structure des prix, prend pourtant en compte le système des préférences et des croyances des individus. Mais il est vrai que les tests empiriques de ces prédictions théoriques ne contrôlent pas l'hétérogénéité des préférences et des croyances individuelles. C'est d'abord sur ces dimensions subjectives des comportements, notamment sur leurs mesures empiriques, que portera principalement notre projet. - Mais comment la théorie économique explique-t-elle cette hétérogénéité des préférences individuelles ? En fait, derrière le voile de l'ignorance, elle suppose ex-ante l'homogénéité des agents : au départ, tous les individus sont identiques (modèle d'Harsanyi). Les différences de goût ne seront alors dues qu'à des différences de parcours et d'environnement. Notre étude s'applique ainsi à étudier ces facteurs individuels qui vont révéler les préférences. - Les questions d'actualité sur le devenir des systèmes collectifs d'assurance sociale concernant la redistribution, le financement des systèmes de retraites, de santé et de chômage, seront au centre de notre étude. - Les liens entre les politiques publiques dans ces domaines et les comportements individuels ne sont pas univoques. D'un côté, les politiques influencent les comportements des individus (offre de travail, épargne pour la retraite, précaution contre le risque de chômage, financement des coûts de la dépendance...) et par là même les inégalités (distribution de revenu, de consommation ou de patrimoine). Inversement, les individus, par leur vote ou par leurs opinions, peuvent agir, en amont, sur ces politiques sociales. - Les données ou enquêtes disponibles ne permettent pas d'avoir accès à ces indicateurs de préférences et d'opinion simultanément aux autres informations socio-économiques. Même s'il existe des données sur les sphères financière et professionnelle des individus, il est essentiel de disposer d'une enquête qui les combine avec des données sur leurs goûts, leur histoire, leur situation dans d'autres domaines (santé, famille, logement, éducation, etc.) et leurs anticipations. La plupart des questions seront donc originales mais pour des raisons de comparaisons internationales, nous reprendrons également certaines formulations d'autres enquêtes, européennes et américaines. - Ce projet propose donc la construction d'une enquête centrée sur la mesure empirique de ces facteurs individuels subjectifs susceptibles d'améliorer notre connaissance des comportements humains (en matière d'épargne et de patrimoine, de santé, de retraite, de chômage, de solidarité, d'inégalités). Ce faisant, on contribuera aussi au débat scientifique commun aux sciences sociales et cognitives sur l'importance des facteurs psychologiques dans la théorie de la décision. -