Publications

2015

• Atomic characterization of Au clusters in vapor-liquid-solid grown silicon nanowires
  
  • Chen Wanghua
  • Pareige Philippe
  • Castro Celia
  • Xu Tao
  • Grandidier B.
  • Stiévenard Didier
  • Roca I Cabarrocas Pere
  Journal of Applied Physics, American Institute of Physics, 2015, 118 (10), pp.104301. (10.1063/1.4930143)
  DOI : 10.1063/1.4930143
• Exploring nanomaterials with 3D electron microscopy
  
  • Ersen O.
  • Florea I.
  • Hirlimann C.
  • Pham-Huu C.
  Materials Today, Elsevier, 2015, 18 (7), pp.395-408. In this review we focus on recent developments in the field of 3D imaging at the nanoscale, when applied to nanomaterials and nanostructures. We demonstrate, by highlighting examples, that recent progress in the use of electron microscopy techniques based on tomography allows one to fill the gap between the development of new materials and their structures and characterization. A special emphasis is put on two new 3D approaches: quantitative and analytical 3D tomography. The first approach gives access to the quantitative exploration of specific parameters within nano-objects and/or nanostructures while the latter, based on electron energy loss spectroscopy, details the 3D chemical composition of such systems at the nanometre scale. (10.1016/j.mattod.2015.04.004)
  DOI : 10.1016/j.mattod.2015.04.004
• Inkjet printing of photopolymerizable small molecules for OLED applications
  
  • Olivier Simon
  • Derue Lionel
  • Geffroy Bernard
  • Ishow Eléna
  • Maindron Tony
  , 2015, 9566, pp.95661N. The elaboration of organic light-emitting diodes (OLEDs) via a solution deposition process turns out to be a cheaper alternative to the vacuum evaporation technique. However the most popular spin-coating wet deposition process mainly used in the semiconductor industry is not applicable for large mother glass substrates used in display applications. The inkjet technology addresses this drawback and appears to be a good solution to produce on a large scale wet deposited OLEDs1. This process has been commonly used for polymer deposition and only a few examples2–4 have demonstrated the possibility of depositing small molecules in functional devices. Deposition of small molecules from inkjet printing is supposed to be easier than polymers because monomers do not show polydispersity and consequently the viscosity of the solution containing the monomers, the ink, is easily controllable in production. This work aims at fabricating OLEDs composed of inkjet-printed hole-transporting molecules and a new class of fluorescent molecules that have been further UV-photopolymerized right after deposition. (10.1117/12.2186995)
  DOI : 10.1117/12.2186995
• A Non-volatile Memory Based on Disordered Graphene
  
  • Loisel Loic
  • Maurice Ange
  • Lebental Bérengère
  • Vezzoli Stefano
  • Cojocaru Costel-Sorin
  • Tay Beng Kang
  , 2015, pp.2p. We report on the demonstration and characterization of a non-volatile graphene-based memory, where the resistance level can be reversibly modulated with a contrast exceeding 400. We study two-terminal devices consisting of highly crystalline (Raman I(D)/I(G) H 0.2) monolayer CVD-graphene micro-ribbons transferred on SiO2 after growth on Cu. Electrical characterizations right after fabrication show the expected Ohmic behavior with k© resistance level and no memory effect. A breakdown technique turns the resistive devices into memories: we apply a voltage sweep up to 30V (a few mA). During the sweep, several moderate jumps in resistance are observed, followed by a final rise to a high resistance state (several M©). As evidenced by Raman mapping, the resulting material is highly disordered graphene (I(D)/I(G) H 1.3) covering the whole device surface. After breakdown, the resistance can be reversibly set at two well-separated levels (e.g. 0.1 M© and 10 M©) by applying low voltage pulses (10V; 1-100 ŒA) in vacuum. Both conductance states feature the Poole-Frenkel conduction mode, as is typical in disordered carbon. No loss of matter or physical gap is observed with either SEM or AFM. Overall, our results suggest that the reversible switching is mostly due to thermally-induced increase or decrease in sp2 grain size in disordered graphene. This is significantly different from the commonly reported switching mechanism based on conducting filaments bridging a physical gap.
• Ultrathin PECVD epitaxial Si solar cells on glass via low-temperature transfer process
  
  • Cariou Romain
  • Chen Wanghua
  • Cosme-Bolanos Ismael
  • Maurice Jean-Luc
  • Foldyna Martin
  • Depauw Valérie
  • Patriarche Gilles
  • Gaucher Alexandre
  • Cattoni Andrea
  • Massiot Ines
  • Collin Stéphane
  • Cadel Emmanuel
  • Pareige Philippe
  • Roca I Cabarrocas Pere
  Progress in Photovoltaics, Wiley, 2015, 24 (8), pp.1075 - 1084. (10.1002/pip.2762)
  DOI : 10.1002/pip.2762
• Optimization of Picrosirius red staining protocol to determine collagen fiber orientations in vaginal and uterine cervical tissues by Mueller polarized microscopy
  
  • Nazac André
  • Bancelin Stéphane
  • Teig Benjamin
  • Haj Ibrahim Bicher
  • Fernandez Hervé
  • Schanne-Klein Marie-Claire
  • de Martino Antonello
  Microscopy Research and Technique, Wiley, 2015, 78 (8), pp.723-730. Polarized microscopy provides unique information on anisotropic samples. In its most complete implementation, namely Mueller microscopy, this technique is well suited for the visualization of fibrillar proteins orientations, with collagen in the first place. However, the intrinsic optical anisotropy of unstained tissues has to be enhanced by Picrosirius Red (PR) staining to enable Mueller measurements. In this work, we compared the orientation mapping provided by Mueller and second harmonic generation (SHG) microscopies on PR stained samples of vaginal and uterine cervix tissues. SHG is a multiphoton technique that is highly specific to fibrillar collagen, and was taken as the gold standard for its visualization. We showed that Mueller microscopy can be safely used to determine collagen orientation in PR stained cervical tissue. In contrast, in vaginal samples, Mueller microscopy revealed orientations not only of collagen but also of other anisotropic structures. Thus PR is not fully specific to collagen, which necessitates comparison to SHG microscopy in every type of tissue. In addition to this study of PR specificity, we determined the optimal values of the staining parameters. We found that staining times of 5min, and sample thicknesses of 5 mu m were sufficient in cervical and vaginal tissues. Microsc. Res. Tech. 78:723-730, 2015. (c) 2015 Wiley Periodicals, Inc. (10.1002/jemt.22530)
  DOI : 10.1002/jemt.22530
• Investigating inhomogeneous electronic properties of radial junction solar cells using correlative microscopy
  
  • Müller Martin
  • Hývl Matěj
  • Kratzer Markus
  • Teichert Christian
  • Misra Soumyadeep
  • Foldyna Martin
  • Yu Linwei
  • Roca I Cabarrocas Pere
  • Itoh Takashi
  • Hájková Zdeňka
  • Vetushka Aliaksei
  • Ledinský Martin
  • Kočka Jan
  • Fejfar Antonín
  Japanese Journal of Applied Physics, Japan Society of Applied Physics, 2015, 54 (8S1). (10.7567/JJAP.54.08KA08)
  DOI : 10.7567/JJAP.54.08KA08
• High structural quality InGaN/GaN multiple quantum well solar cells
  
  • Dogmus Ezgi
  • Zegaoui Malek
  • Largeau Ludovic
  • Tchernycheva Maria
  • Neplokh Vladimir
  • Weiszer Saskia
  • Schuster Fabian
  • Stutzmann Martin
  • Foldyna Martin
  • Medjdoub F
  Physica Status Solidi C: Current Topics in Solid State Physics, Wiley, 2015. (10.1002/pssc.201510137)
  DOI : 10.1002/pssc.201510137
• Small molecule-based photocrosslinkable fluorescent materials toward multilayered and high-resolution emissive patterning
  
  • Olivier Simon
  • Derue Lionel
  • Geffroy Bernard
  • Maindron Tony
  • Ishow Eléna
  Journal of Materials Chemistry, Royal Society of Chemistry, 2015, 3, pp.8403-8412. a Solution-processable green and red-emitting fluorophores possessing photopolymerizable acrylate units have been synthesized. Photocrosslinking was successfully performed in neat thin films at room temperature under low-dose UV irradiation at 365 nm. No further curing step was necessary to achieve insoluble emissive thin films displaying high optical quality. Up to 80% of the green emitting material processed as a non-doped thin film remained after photopolymerization. Despite competitive energy transfer occurring between the excited photoinitiator and the radiative excited state of red-emitting materials, up to 40% of the initial thickness could be achieved after development. The very low RMS roughness of the green and red photocrosslinked thin films after development (RMS o 0.7 nm) allowed us to fabricate multicolored stacks again with high optical quality (RMS roughness o 1.3 nm) after two cycles of irradiation and development involving successively red and green emitters. Resolved patterns as small as 600 nm in width could be obtained upon photolithography performed under an air atmosphere. High adhesion of the photocrosslinked materials on surfaces makes the resulting emissive thin films very promising for realizing complex emissive structures on flat or bend substrates as required in multiple applications such as optical data storage, organic lasers, organic light emitting diodes or counterfeiting. (10.1039/c5tc01453k)
  DOI : 10.1039/c5tc01453k
• Ink-jet printing NiO for efficient p-type and tandem DSSC
  
  • Brisse Romain
  • Faddoul Rita
  • Kaeffer Nicolas
  • Palacin Serge
  • Artero Vincent
  • Geffroy Bernard
  • Berthelot Thomas
  • Gustavsson Thomas
  • Jousselme Bruno
  , 2015.
• Bridged alpha,omega-bis(dicyanovinyl)quaterthiophenes for photovoltaic applications
  
  • Baert François
  • Cabanetos Clément
  • Leliège Antoine
  • Kirchner Eva
  • Segut Olivier
  • Alévêque Olivier
  • Allain Magali
  • Gijun Seo
  • Jung Sungyeop
  • Tondelier Denis
  • Geffroy Bernard
  • Roncali Jean
  • Leriche Philippe
  • Blanchard Philippe
  , 2015.
• Mesures et modélisation du comportement de panneaux photovoltaïques en environnement réel
  
  • Badosa Jordi
  • Bourdin Vincent
  • Jaffré Alexandre
  • Migan-Dubois Anne
  • Nassar Joaquim
  • Pavlov Marko
  • Pons Michel
  , 2015.
• Equivalent Circuit Modeling for a High-Performance Large-Area Organic Photovoltaic Module
  
  • Kim Chang-Hyun
  • Beliatis Michail J.
  • Gandhi Keyur K.
  • Rozanski Lynn J.
  • Bonnassieux Yvan
  • Horowitz Gilles
  • Silva S. Ravi P.
  IEEE Journal of Photovoltaics, IEEE, 2015, 5 (4), pp.1100-1105. For organic photovoltaics (OPVs) to contribute significantly to energy generation, they need to be scaled to large areas, much like all organic electronics. Therefore, there is a need for the development of a specific model that describes the electrical properties related to the size effects and cell interconnections. We report here on the equivalent circuit models for a high-performance series-connected OPV module based on a polymer:fullerene bulkheterojunction formulation. We examine the validity of the effective single cell methodology in the conventional framework and suggest a modified model that includes the net series resistance and additional parasitic leakage conductions. The photocurrent is found to follow the diffusion-limited voltage dependence, for which an empirical treatment enables an improved reproduction of the measurement near the short-circuit point. (10.1109/JPHOTOV.2015.2419136)
  DOI : 10.1109/JPHOTOV.2015.2419136
• Donor/Acceptor Dihydroindeno[1,2-a]fluorene and Dihydroindeno[2,1-b]fluorene: Towards New Families of Organic Semiconductors
  
  • Romain Maxime
  • Jeannin Olivier
  • Rault-Berthelot Joëlle
  • Poriel Cyril
  • Tondelier Denis
  • Geffroy Bernard
  • Jacques Emmanuel
  Chemistry, Wiley, 2015, 21 (26), pp.9426-9439. New families of donor/acceptor semiconductors based on dihydroindeno[1,2-a]fluorene and dihydroindeno[2,1-b]fluorene are reported. Due to the spiro bridges, this new generation of dihydroindenofluorenes allows a spatial separation of HOMO and LUMO, which retains the high ET value of the dihydroindenofluorene backbone and excellent physical properties. This control of the electronic and physical properties has allowed a second generation of dihydroindeno[1,2-a]fluorene to be obtained with strongly enhanced performance in green and sky-blue phosphorescent organic light-emitting diodes (PhOLEDs) relative to the first generation of materials. To date, this is the highest performance ever reported for a blue PhOLED by using a dihydroindenofluorene derivative. Through this structure-property relationship study, a remarkable difference of performance between syn and anti isomers has also been highlighted. This surprising behaviour has been attributed to the different symmetry of the two molecules, and highlights the importance of the geometry profiles in the design of host materials for PhOLEDs. (10.1002/chem.201500336)
  DOI : 10.1002/chem.201500336
• SiGe Low Temperature Epitaxy by PECVD on III-V MOVPE Grown Material for High Efficiency Tandem Solar Cell Applications
  
  • Decobert Jean
  • Cariou Romain
  • Louarn Kevin
  • Fortin Catherine
  • Lachaume Raphaël
  • Alvarez J
  • Kleider Jean-Paul
  • Foldyna Martin
  • Cabarrocas Pere Roca I.
  , 2015.
• Phosphorus-based chromophores: Emitters for OLEDs
  
  • Duffy Matthew P.
  • Bouit Pierre-Antoine
  • Geffroy Bernard
  • Tondelier Denis
  • Hissler Muriel
  Phosphorus, Sulfur, and Silicon and the Related Elements, Taylor & Francis, 2015, 190 (5-6), pp.845-853. In this paper, we present the development of white OLEDs (WOLEDs) using organophosphorus derivatives as fluorescent emitters. The structural changes that we have performed on and around the phosphole ring (functionalization of the phosphorus atom, nature of the substituents at the 2 and 5 position) allow the ability to tune the emission wavelengths and the color emitted by the OLEDs. Using this concept, we developed organophosphorus dopants emitting orange light, which can be mixed with a blue emitting matrix for the development of WOLEDs. The OLEDs structure allows the development of flexible OLEDs with good performance and CIE coordinates which are independent from the current density. (10.1080/10426507.2014.980414)
  DOI : 10.1080/10426507.2014.980414
• Boosting light emission from Si-based thin film over Si and SiO_2 nanowires architecture
  
  • Yu Zhongwei
  • Qian Shengyi
  • Yu Linwei
  • Misra Soumyadeep
  • Zhang Pei
  • Wang Junzhuan
  • Shi Yi
  • Xu Ling
  • Xu Jun
  • Chen Kunji
  • Roca I Cabarrocas Pere
  Optics Express, Optical Society of America - OSA Publishing, 2015, 23 (5). (10.1364/OE.23.005388)
  DOI : 10.1364/OE.23.005388
• Synthèse des activités photovoltaïques au SIRTA
  
  • Migan-Dubois Anne
  • Badosa Jordi
  • Lapouge F.
  • Nassar Joaquim
  • Mambrini Thomas
  • Pavlov Marko
  • Bourdin Vincent
  , 2015.
• Wireless nanosensors for embedded measurement in concrete structures
  
  • Michelis Fulvio
  • Bodelot Laurence
  • Laheurte Jean-Marc
  • Zaki Fadi
  • Bonnassieux Yvan
  • Lebental Bérengère
  , 2015, pp.6p. In this work we propose a wireless architecture for embedded monitoring in concrete. The modular structure of the system allows it to be adapted to different types of sensors. We present the application of such architecture for the detection of microcracks in concrete. A carbon nanotube strain sensor recently developed by the group is used to track mechanical deformations. Full temperature compensation is achieved by a specific conditioning circuit.
• Nanosensors for embedded monitoring of construction materials: the '2D conformable' route
  
  • Lebental Bérengère
  • Ghaddab Boutheina
  • Michelis Fulvio
  , 2015, pp.6p. We propose an approach to embedded monitoring of construction materials relying on 2D, conformable architectures that are expected to be lower cost and more robust than their 3D counterparts. In this article, we present two examples: a RFID-enabled carbon nanotube strain sensor on plastic for microcrack monitoring in concrete and a nanoparticle-asphalt sandwich for weigh-in-motion applications.
• Etude de nanofils de silicium comme matériau d'électrode négative de batterie lithium-ion
  
  • Lucie Leveau
  , 2015. Le silicium est un matériau d’électrode prometteur pour augmenter la capacité de stockage des batteries Li-ion. Il subit malheureusement d’importantes variations de volume lors du cyclage qui diminuent la durée de vie des électrodes. Une des clés pour remédier à ce problème est l’utilisation de nanofils de silicium, synthétisés par dépôt chimique en phase vapeur, pouvant accommoder plus facilement ces variations de volume. La thèse présentée ici s’attache à étudier les performances de ce nouveau type d’électrode et les possibilités d’amélioration en vue d’une utilisation en batterie Li-ion. Dans un premier temps, des analyses par résonance magnétique nucléaire (RMN), spectroscopie de perte d’énergie des électrons et tomographie électronique ont été effectuées à différents stades du premier cycle afin d’étudier l’insertion et l’extraction du lithium dans ce matériau. Différentes stratégies de cyclage ont ensuite été abordées pour augmenter la durée de vie. Des analyses ex-situ d’électrodes par microscopie électronique et RMN ont alors permis de mieux comprendre le vieillissement, mettant notamment en évidence la dégradation continue de l’électrolyte sur le silicium qui est à l’origine d’une consommation irréversible de lithium. La prélithiation des électrodes apparaît comme une voie prometteuse pour remédier à ce problème. Enfin, de nouvelles structures plus denses à base de nano-arbres de silicium ont été synthétisées et ont permis de multiplier par plus d’un facteur 6 la capacité surfacique. Ce travail ouvre ainsi des perspectives intéressantes pour l’élaboration de cellules lithium-ion complètes de grande densité d’énergie utilisant une anode de silicium nanostructurée.
• Realistic modeling of tandem cells formed by low temperature PECVD epitaxy of silicon-germanium on gallium arsenide
  
  • Lachaume Raphaël
  • Cariou Romain
  • Decobert Jean
  • Foldyna Martin
  • Hamon Gwenaelle
  • Cabarrocas Pere Roca I.
  • Alvarez J
  • Kleider Jean-Paul
  , 2015. Multijunction solar cells based on III-V compounds have by far the highest conversion efficiency. However, the fabrication cost is very high. An attractive solution to lower the cost while maintaining high efficiencies is to design multijunctions on cheaper substrates such as silicon [1]. Different routes have been taken to cope with lattice mismatch issues between Si and III-Vs: epitaxial growth of GaAs on Si with or without buffer layers or non-epitaxial techniques such as mechanical stacking. A novel approach has been recently presented consisting in direct epitaxial growth of thin Si or SiGe layers on GaAs by low temperature PECVD [2], where the high crystal quality reported opens a new way for making III-V/Si tandem solar cells. For a given thickness of the epi-Si or epi-SiGe bottom cell (typically less than 5 µm), it is crucial to find the optimum composition of the III-V top cell. This depends on both optical and electrical properties of the entire structure. Actually, the common efficiency calculations are based on the ideal radiative limit [1] and suffer from limiting assumptions, e.g. complete absorption in the sub-cells, no non-radiative recombination in the bottom cell. In this paper we thus propose an extensive numerical simulation study using TCAD tools to calculate realistic maximum efficiencies and facilitate the design of III-V/epi-SiGe tandem cells. [1] J. Connolly et al., Prog. Photovolt: Res. Appl 22 (2014) 810 [2] R. Cariou et al., 40th IEEE PVSC (2014)
• Difluorinated 6,13-Bis(triisopropylsilylethynyl)pentacene: Synthesis, Crystallinity, and Charge-Transport Properties
  
  • Kim Chang-Hyun
  • Hlaing Htay
  • Payne Marcia
  • Parkin Sean
  • Anthony John E.
  • Kymissis Ioannis
  ChemPhysChem, Wiley-VCH Verlag, 2015, 16 (6), pp.1251–1257. Fluorination has been demonstrated to improve stability and processing in thiophene-containing small-molecule semiconductors. Here, the impact of partial fluorination on these parameters in a pentacene derivative is examined. Although the improvement in photostability is not as dramatic, there is a clear improvement in the stability of the chromophore upon fluorination. The improvement in processability is more dramatic; devices formed by spin-coating with the fluorinated derivative perform substantially better than those formed from the nonfluorinated compound. (10.1002/cphc.201402750)
  DOI : 10.1002/cphc.201402750
• Photocathodes based on organic semiconductors coupled to a MoS3 catalyst for solar hydrogen production
  
  • Bourgeteau Thiphaine
  • Tondelier Denis
  • Geffroy Bernard
  • Artero Vincent
  • Jousselme Bruno
  , 2015.
• Lifetime assessment in crystalline silicon: From nanopatterned wafer to ultra-thin crystalline films for solar cells
  
  • Cosme I.
  • Cariou R.
  • Chen W.
  • Foldyna M.
  • Boukhicha R.
  • Roca I Cabarrocas P.
  • Lee K.D.
  • Trompoukis C.
  • Depauw V.
  Solar Energy Materials and Solar Cells, Elsevier, 2015, 135 (3). (10.1016/j.solmat.2014.10.019)
  DOI : 10.1016/j.solmat.2014.10.019