A bridged low band gap A-D-A quaterthiophene as efficient donor for organic solar cells

International audience[small alpha],[small omega]-Bis(dicyanovinyl)quaterthiophene 1 with a median 4,4-diethyl-4H-cyclopenta[2,1-b:3,4-b[prime or minute]]dithiophene has been synthesized. UV-Vis absorption data show that the covalent bridging of the inner 2,2[prime or minute]-bithiophene leads to a significant reduction of the HOMO-LUMO gap essentially due to an increase of the HOMO level as confirmed by electrochemical and theoretical results. X-ray diffraction analysis of a single crystal of 1 shows that except for the out-of-plane ethyl groups, the conjugated system displays a quasi-planar geometry while the molecular packing exhibits strong [small pi]-stacking interactions and multiple short intermolecular contacts. Quaterthiophene 1 has been used as active donor material in organic solar cells of various architectures including bi-layer planar hetero-junctions and hybrid co-evaporated bulk hetero-junctions with C60 as electron acceptor material. A maximum conversion efficiency of 4.30% is obtained with a hybrid co-evaporated device. These results are discussed in terms of structure-properties relationships with reference to the open-chain parent [small alpha],[small omega]-bis(dicyanovinyl)quaterthiophene 2

The ArT\'eMiS wide-field submillimeter camera: preliminary on-sky performances at 350 microns

ArTeMiS is a wide-field submillimeter camera operating at three wavelengths simultaneously (200, 350 and 450 microns). A preliminary version of the instrument equipped with the 350 microns focal plane, has been successfully installed and tested on APEX telescope in Chile during the 2013 and 2014 austral winters. This instrument is developed by CEA (Saclay and Grenoble, France), IAS (France) and University of Manchester (UK) in collaboration with ESO. We introduce the mechanical and optical design, as well as the cryogenics and electronics of the ArTeMiS camera. ArTeMiS detectors are similar to the ones developed for the Herschel PACS photometer but they are adapted to the high optical load encountered at APEX site. Ultimately, ArTeMiS will contain 4 sub-arrays at 200 microns and 2x8 sub-arrays at 350 and 450 microns. We show preliminary lab measurements like the responsivity of the instrument to hot and cold loads illumination and NEP calculation. Details on the on-sky commissioning runs made in 2013 and 2014 at APEX are shown. We used planets (Mars, Saturn, Uranus) to determine the flat-field and to get the flux calibration. A pointing model was established in the first days of the runs. The average relative pointing accuracy is 3 arcsec. The beam at 350 microns has been estimated to be 8.5 arcsec, which is in good agreement with the beam of the 12 m APEX dish. Several observing modes have been tested, like On-The-Fly for beam-maps or large maps, spirals or raster of spirals for compact sources. With this preliminary version of ArTeMiS, we concluded that the mapping speed is already more than 5 times better than the previous 350 microns instrument at APEX. The median NEFD at 350 microns is 600 mJy.s1/2, with best values at 300 mJy.s1/2. The complete instrument with 5760 pixels and optimized settings will be installed during the first half of 2015.Comment: 11 pages, 11 figures. Presented at SPIE Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VII, June 24, 2014. To be published in Proceedings of SPIE Volume 915

Large bolometer arrays with superconducting NbSi sensors for future space experiments

International audienceNew techniques in microelectronics allow to build large arrays of bolometers filling the focal plane of submillimeter and millimeter telescopes. The expected sensitivity increase is the key for the next generation of space experiments in this wavelength range. Superconducting bolometers offer currently the best prospects in terms of sensitivity and multiplexed readout. We present here the developments led in France based on NbSi alloy thermometers. The manufacturing process of a 23 pixel array and the test setup are described

Guelb el Ahmar (Bathonian, Anoual Syncline, eastern Morocco): First continental flora and fauna including mammals from the Middle Jurassic of Africa

We report the discovery in Mesozoic continental “red beds” of Anoual Syncline, Morocco, of the new Guelb el Ahmar (GEA) fossiliferous sites in the Bathonian Anoual Formation. They produced one of the richest continental biotic assemblages from the Jurassic of Gondwana, including plants, invertebrates and vertebrates. Both the sedimentological facies and the biotic assemblage indicate a lacustrine depositional environment. The flora is represented by tree trunks (three families), pollen (13 species, five major clades) and charophytes. It suggests local forests and humid (non-arid) conditions. The vertebrate fauna is dominated by microvertebrates recovered by screening–washing. It is rich and diverse, with at least 29 species of all major groups (osteichthyans, lissamphibians, chelonians, diapsids, mammals), except chondrichthyans. It includes the first mammals discovered in the Middle Jurassic of Arabo-Africa. The GEA sites yielded some of the earliest known representatives of osteoglossiform fishes, albanerpetontid and caudate amphibians, squamates (scincomorphans, anguimorphan), cladotherian mammals, and likely choristoderes. The choristoderes, if confirmed, are the first found in Gondwana, the albanerpetontid and caudatan amphibians are among the very few known in Gondwana, and the anguimorph lizard is the first known from the Mesozoic of Gondwana. Mammals (Amphitheriida, cf. Dryolestida) remain poorly known, but are the earliest cladotherians known in Gondwana. The GEA biotic assemblage is characterized by the presence of Pangean and Laurasian (especially European) taxa, and quasi absence of Gondwanan taxa. The paleobiogeographical analysis suggests either a major fossil bias in Gondwana during the Middle Jurassic, and an overall vicariant Pangean context for the GEA assemblage, or alternatively, noticeable Laurasian (European) affinities and North-South dispersals. The close resemblance between the Bathonian faunas of GEA and Britain is remarkable, even in a Pangean context. The similarity between the local Anoual Syncline Guelb el Ahmar and Ksar Metlili faunas raises questions on the ?Berriasian age of the latter

Synthèse et étude de systèmes conjugués pour le photovoltaïque organique

Les systèmes conjugués sont depuis une vingtaine d'années très étudiés pour leurs propriétés optoélectroniques et leur versatilité synthétique qui permettent leur incorporation dans des composants électroniques organiques. Parmi ceux-ci, les cellules solaires organiques en hétérojonction à base de chromophores donneur et accepteur d'électrons font l'objet d'un intérêt grandissant. Dans ce contexte, le travail présenté porte sur la synthèse et l'étude de systèmes moléculaires conçus pour une incorporation en tant que donneurs d'électrons dans des cellules solaires organiques. Le premier chapitre rappelle l'historique des cellules solaires puis s'attache à décrire en détails les fonctionnements, avantages et limitations des composants organiques. La seconde partie du chapitre est consacrée à la description de cellules solaires " en réseaux interpénétrés " dans lesquelles donneur et accepteur d'électrons sont intimement mélangés avec en particulier l'incorporation de dérivés moléculaires comme donneurs d'électrons dans ces dispositifs. Les deux chapitres suivants sont consacrés aux synthèses et études de composés de la famille de la triphénylamine ( TPA ). Le chapitre deux traite de TPA substituées par des groupes susceptibles d'engendrer de fortes interactions intermoléculaires alors que le chapitre trois s'intéresse à l'amélioration des propriétés spectroscopiques et électroniques par modification structurale des TPA. Dans ces chapitres, la synthèse et les études des produits sont présentées. Le dernier chapitre est consacré à des dérivés du dicétopyrrolopyrrole ( DPP ). Après un rappel bibliographique, les synthèses et propriétés de DPP fonctionnalisés sont présentées.Conjugated systems have been widely studied for 20 years for their optoelectronic properties and synthetic versatility that allow incorporation into various organic electronic devices ( OSCs, OLEDs, OFETs ... ). A growing interest in organic heterojunction solar celles based on chromophoric electron donors and acceptors is noted. In this context, the work presented in this manuscript focuses on the synthesis and study of molecular systems incorporable as donor in organic photovoltaic cells. The first chapter begins with a brief recall of solar cells history followed by the description of the workings, avantages and limitations of organic devices. The second part of this chapter is devoted to the description of bulk heterojunction solar cells ( BHJ-SC ) in which interpenetrating networks of donor and acceptor are intimately mixed. A particular focus is dedicated to BHJ-SC based on molecular systems. The two next chapters are devoted the synthesis and study of compounds of the triphenylamine ( TPA ) family. Chapter two deals with the synthesis of TPA susbtituted with groups able to promote strong intermolecular interactions, while the third chapter focuses on the improvement of spectroscopic and electronic properties by structural modification in those systems. In both part, synthesis, spectroscopic, electrochemical and theoretical studies are presented. The fourth and final chapter is dedicated to the diketopyrrolopyrrole ( DPP ) core. After a brief state of the art, the synthesis and properties of a serie of products are detailed.ANGERS-BU Lettres et Sciences (490072106) / SudocSudocFranceF