Hyperbranched Quasi-1D TiO2 Nanostructure for Hybrid Organic-Inorganic Solar Cells

The performance of hybrid solar cells is strongly affected by the device morphology. In this work we demonstrate a Poly(3-hexylthiophene-2,5-diyl)/TiO2 hybrid solar cell where the TiO2 photoanode comprises an array of tree-like hyperbranched quasi-1D nanostructures self-assembled from the gas phase. This advanced architecture enables us to increase the power conversion efficiency to over 1%, doubling the efficiency with respect to state of the art devices employing standard mesoporous titania photoanodes. This improvement is attributed to several peculiar features of this array of nanostructures: high interfacial area; increased optical density thanks to the enhanced light scattering; and enhanced crystallization of Poly(3-hexylthiophene-2,5-diyl) inside the quasi-1D nanostructure

Photoemission Spectroscopy and Atomic Force Microscopy Investigation of Vapor Phase Co-Deposited Silver/Poly(3-hexylthiophene) Composites

Nanocomposite matrices of silver/poly(3-hexylthiophene) (P3HT) were prepared in ultrahigh vacuum through vapor-phase co-deposition. Change in microstructure, chemical nature and electronic properties with increasing filler (Ag) content were investigated using in-situ XPS and UPS, and ambient AFM. At least two chemical binding states occur between Ag nanoparticles and sulfur in P3HT at the immediate contact layer but no evidence of interaction between Ag and carbon (in P3HT) was found. AFM images reveal a change in Ag nanoparticles size with concentration which modifies the microstructure and the average roughness of the surface. Under co-deposition, P3HT largely retains its conjugated structures, which is evidenced by the similar XPS and UPS spectra to those of P3HT films deposited on other substrates. We demonstrate here that the magnitude of the barrier height for hole injection and the position of the highest occupied band edge (HOB) with respect to the Fermi level of Ag can be controlled and changed by adjusting the metal (Ag) content in the composite. Furthermore, UPS reveals distinct features related to the C 2p (Sigma states) in the 5-12 eV regions, indicating the presence of ordered P3HT which is different from solution processed films.Comment: Scudier and Wei provided equal contributio

Simple Approach to Hybrid Polymer/Porous Metal Oxide Solar Cells from Solution-Processed ZnO Nanocrystals

This work is devoted to the development of hybrid bulk heterojunction solar cells based on porous zinc oxide (ZnO) electrodes and poly(3-hexylthiophene) (P3HT), using simple synthesis procedures and deposition techniques. Starting from ZnO nanocrystals with well-controlled properties, porous ZnO electrodes of suitable porosity are deposited by spin-coating, varying the main experimental parameters such as composition of the initial ZnO formulation and choice of the organic ligand. Significant charge transfer yields are observed in the corresponding solar cells, and the influence of processing conditions on device performance is investigated using conventional techniques as well as transient photovoltage/photocurrent decay measurements. The temperature used to sinter the ZnO electrode is found to be specifically crucial to ensure efficient charge transport in the device while avoiding a loss in interfacial area through nanocrystal coalescence. Using 8 × 13 nm ZnO nanorods, the best device exhibits a power conversion efficiency of 0.35% under 100 mW·cm -2 AM1.5G simulated solar emission. This strategy, using processing in air with simple deposition techniques, competes with related approaches based on nanostructured ZnO processed using more complex procedures. Moreover, device performance and photophysics are found to be greatly influenced by the morphology of the starting ZnO nanocrystals, illustrating that fine control of the inorganic component can effectively tune the performance of hybrid bulk heterojunction solar cells. © 2010 American Chemical Society

Transfer Learning for Prostate Cancer Mapping Based on Multicentric MR Imaging Databases

International audienceThis paper addresses the issue of fusing datasets coming from different imaging protocols or scanners to boost the performance of computer aided diagnostic system. We present novel contributions in the field of subspace alignment methods that are part of domain adaptation framework. We first introduce a simple approach based on scaling the features of the different distribution and accounting for the class information. We also extend an unsupervised landmark based approach that has been recently developed to the supervised setting. These methods are evaluated in the context of prostate cancer screening based on two patient MRI databases acquired on different scanners. We demonstrate promising performance of the scaling based method when both databases contain similar number of annotated samples, and stable performance of the landmark based method even with unbalanced datasets

Suivi de la ZRV de type « bassin » de Marguerittes (30). Bilan du fonctionnement à débit Q1 et Q2

La conception de la ZRV de Marguerittes est détaillée dans le document qui décrit le contexte général de création de cette ZRV (Boutin et Walaszek, 2014). Les périodes d'acquisition des données analysées sont différentes selon les paramètres : (données hydriques, Paramètres chimiques : Majeurs sous forme de prélèvements ponctuels et bilans 24h ou enregistrement en continu, Micropolluants, prélèvements de dépôts par bathymétrie, Indicateurs de contamination fécale, Végétaux). Le compartiment « sol » n'est pas étudié sur ce site, les bassins ayant été étanchéifiés. Ce rapport s'attache à présenter les résultats et analyses du suivi de la ZRV de Marguerittes selon les aspects hydrauliques et des évolutions de qualité des différents paramètres physicochimiques contenues dans les eaux, sans exclure les boues. Une conclusion sous forme de bilan de masse, intègre les résultats du compartiment « végétal »