Publications

2017

• On the Mechanism of In Nanoparticle Formation by Exposing ITO Thin Films to Hydrogen Plasmas
  
  • Fan Zheng
  • Maurice Jean-Luc
  • Chen Wanghua
  • Guilet Stephane
  • Cambril Edmond
  • Lafosse Xavier
  • Couraud Laurent
  • Merghem Kamel
  • Yu Linwei
  • Bouchoule Sophie
  • Roca I Cabarrocas Pere
  Langmuir, American Chemical Society, 2017, 33 (43), pp.12114-12119. (10.1021/acs.langmuir.7b01743)
  DOI : 10.1021/acs.langmuir.7b01743
• Epitaxial growth of silicon by PECVD from SiF4/H2/Ar gas mixtures for photovoltaics
  
  • Leal Ronan
  , 2017. This doctoral work aimed to assess the potential of low-temperature (200-300°C) epitaxy by plasma-enhanced chemical vapor deposition (PECVD) using SiF4/H2/Ar gas mixtures for the emitter formation in nPERT solar cells. The first part of this PhD thesis concerned the identification and the optimization of the process conditions to perform lowly strained intrinsic epi-layers with a smooth epi/wafer interface. We also investigated the causes of epitaxy breakdown and found out that a twinning-induced mechanism was responsible. Subsequently we focused on the growth mechanisms by studying the initial stages of growth and a Volmer-Weber growth mode has been highlighted. Finally, the process conditions for intrinsic epitaxy were transferred from a researchPECVD reactor to a 6 inch semi-industrial one. Inhomogeneity and growth rate issues have been tackled by fluid dynamics simulations resulting in the design of a new shower head. Boron-doped epi-layers grown at 300°C with an as-deposited hole concentration of 4.1019 cm-3 and a doping efficiency up to 70 % have been achieved keeping a low mosaicity and a low variation of the lattice parameter. The growth rate in these conditions reached 1.1 Å/s, i.e 15 times higher than what obtained at the beginning of this PhD for boron-doped epi-layers. Finally, the passivation of epitaxial layers has been investigated and lifetimes up to 160 μs for a 200 nm thick intrinsic layer passivated with
• InGaN/GaN nanowire flexible light emitting diodes and photodetectors
  
  • Guan Nan
  • Dai Xing
  • Zhang Hezhi
  • Mancini Lorenzo
  • Kapoor Akanksha
  • Bougerol Catherine
  • Julien François
  • Cavassilas Nicolas
  • Foldyna Martin
  • Durand Christophe
  • Eymery J.
  • Tchernycheva Maria
  , 2017. (10.1109/ICTON.2017.8024808)
  DOI : 10.1109/ICTON.2017.8024808
• Low temperature plasma epitaxy of Silicon on III-V for tandem solar cells
  
  • Hamon Gwenaelle
  • Vaissière Nicolas Vaissiere
  • Cariou Romain
  • Chen Wanghua
  • Foldyna Martin
  • Lachaume Raphaël
  • Maurice Jean-Luc
  • Alvarez José
  • Decobert Jean
  • Kleider Jean-Paul
  • Cabarrocas Pere Roca I.
  , 2017.
• A Solar Cell Architecture for Enhancing Performance While Reducing Absorber Thickness and Back Contact Requirements
  
  • Fonash Stephen
  • Nam Wook Jun
  • Dornstetter Jean-Christophe
  • Al-Ghzaiwat Mutaz
  • Foldyna Martin
  • Roca I Cabarrocas Pere
  IEEE Journal of Photovoltaics, IEEE, 2017, 7 (4), pp.974 - 979. (10.1109/JPHOTOV.2017.2703854)
  DOI : 10.1109/JPHOTOV.2017.2703854
• Inverse metamorphic III-V/epi-SiGe tandem solar cell performance assessed by optical and electrical modeling
  
  • Lachaume Raphaël
  • Foldyna Martin
  • Hamon Gwenaelle
  • Vaissière Nicolas Vaissiere
  • Decobert Jean
  • Cariou Romain
  • Roca I Cabarrocas Pere Roca I Cabarrocas
  • Alvarez J
  • Kleider Jean-Paul
  , 2017.
• Step-by-step evaluation of photovoltaic module performance related to outdoor parameters: evaluation of the uncertainty
  
  • Migan-Dubois Anne
  • Badosa Jordi
  • Calderón Obaldía Fausto
  • Atlan Olivier
  • Bourdin Vincent
  • Pavlov Marko
  • Young Kim Dae
  • Bonnassieux Yvan
  , 2017, pp.626-631. Knowing the uncertainty in the PV production forecast is crucial in the optimization of smart-grid operations and in its stability. In this paper, we present uncertainty calculation in the PV energy production forecast process, calculated step by step. From horizontal irradiance and ambient temperature, all the steps needed to evaluate the PV production are studied with a special focus on the comparison between calculation and measurements. The uncertainty is evaluated by computing the relative mean bias error and the relative mean absolute error. (10.1109/PVSC.2017.8366615)
  DOI : 10.1109/PVSC.2017.8366615
• Structural Instabilities Related to Highly Anharmonic Phonons in Halide Perovskites
  
  • Marronnier Arthur
  • Lee Heejae
  • Geffroy Bernard
  • Even Jacky
  • Bonnassieux Yvan
  • Roma Guido
  Journal of Physical Chemistry Letters, American Chemical Society, 2017, 8 (12), pp.2659–2665. Hybrid perovskites have emerged over the past five years as absorber layers for novel high-efficiency low-cost solar cells combining the advantages of organic and inorganic semiconductors. Unfortunately, electrical transport in these materials is still poorly understood. Employing the linear response approach of density functional theory, we reveal strong anharmonic effects and a double-well phonon instability at the center of the Brillouin zone for both cubic and orthorhombic phases of inorganic CsPbI3. Previously reported soft phonon modes are stabilized at the actual lower-symmetry equilibrium structure, which occurs in a very flat energy landscape, highlighting the strong competition between the different phases of CsPbI3. Factoring these low-energy phonons into electron–phonon interactions and band gap calculations could help better understand the electrical transport properties in these materials. Furthermore, the perovskite oscillations through the corresponding energy barrier could explain the underlying ferroelectricity and the dynamical Rashba effect predicted in halide perovskites for photovoltaics. (10.1021/acs.jpclett.7b00807)
  DOI : 10.1021/acs.jpclett.7b00807
• Circularly polarized OLED based on thermally activated delayed fluorescence molecules
  
  • Feuillastre Sophie
  • Pauton Mathilde
  • Gao Longhui
  • Desmarchelier Alaric
  • Pieters Grégory
  • Riives Adrian J
  • Muller Gilles
  • Clavier Gilles
  • Tondelier Denis
  • Geffroy Bernard
  , 2017. Organic Light-Emitting Diodes (OLEDs) have already entered the mass production market in small size displays (smart phone…) or larger display devices for OLED televisions. However, the request in the market continues to grow for low-power consumption, low-cost and flexible devices. Direct emission of circularly polarized light from OLEDs can improve the contrast ratio of the OLED display, increase the efficiency and simplify device architecture. Circularly polarized luminescence (CPL) emitters represent an important family of molecules, where efficient and easy syntheses, high quantum yields and dissymmetry factors are key challenges. Purely organic CPL emitters are often tedious to synthesize and require chiral purification methods. The development of thermally activated delayed fluorescence (TADF) materials for optoelectronic applications is an active area of recent research . TADF emitters are a class of fluorophore that enable harvesting triplet states for fluorescent emission by a reverse intersystem-crossing phenomenon. This allows maximal emission efficiencies, especially in organic electroluminescent devices (OLEDs) that generate 75% triplet exciton. We have developed a class of purely organic luminophore that combines CPL with TADF in a modular design, and exhibits attractive photophysical properties. This presentation will disclose the concept, preparation, and properties of this new class of molecules, and present their application in OLED devices. Structure-properties relationships have also been explored and will be discussed. Abstract: Thermally activated delayed fluorescence (TADF) emitters are a class of fluorophores that enable harvesting triplet states for light emission by a reverse intersystem crossing phenomenon. This allows theoretically maximal emission efficiencies, especially in organic electroluminescent devices (OLEDs) that generate 75% triplet excitons.
• Estimation de l'incertitude lors de la prévision de la production d'énergie d'origine photovoltaïque pour améliorer l'efficacité et la gestion d'un micro-réseau
  
  • Migan-Dubois Anne
  • Calderón Obaldía Fausto
  • Badosa Jordi
  • Bourdin Vincent
  • Bonnassieux Yvan
  • Dumbia Lassina
  , 2017.
• Solar energy predictability for photovoltaic management applications
  
  • Badosa Jordi
  • Migan-Dubois Anne
  • Bourdin Vincent
  • Calderón Obaldía Fausto
  • Atlan Olivier
  • Pavlov Marko
  • Kim Daeyoung
  • Haeffelin Martial
  • Bonnassieux Yvan
  , 2017.
• Optimizing tin dioxide nanoparticles distribution for silicon nanowires growth
  
  • Dai Letian
  • Al-Ghzaiwat Mutaz
  • Chen Wanghua
  • Foldyna Martin
  • Maurin Isabelle
  • Levtchenko Alexandra
  • Le Gall Sylvain
  • Lachaume Raphaël
  • Alvarez J
  • Kleider Jean-Paul
  • Maurice J.-L.
  • Cabarrocas P.Roca I
  • Gacoin Thierry
  , 2017.
• Mesure de la permittivité du a-Si:H entre 0.5 et 3 THz
  
  • Zerounian N.
  • Grimault-Jacquin A. S.
  • Aniel Frédéric
  • Kleider Jean-Paul
  • Cabarrocas P.Roca I
  , 2017.
• New exotic nanostructured materials : Theoretical predictions and experimental verifications
  
  • Jardali Fatme
  , 2017. This thesis is devoted to the study of advanced, exotic forms of nanostructured materials that could lead to the next big advance for nanodevices. Two distinct topics have been considered. The first one is related to plasma-born aromatic silicon nanoclusters (SiNCs), while the second is dedicated to two-dimensional silicon and germanium materials. Based on molecular dynamics simulations and ab initio calculations, as well as, on experimental investigations, we explore a variety of intriguing properties of those exotic materials that are expected to be far superior to those of their conventional counterparts.In the first part of the thesis, we begin with theoretical studies and show that it is possible to obtain aromatic behavior in simple hydrogenated SiNCs with size of ~1nm. We demonstrate that low-temperature silane/hydrogen plasmas close to dust formation present the ideal environment to exploit the natural tendency of silicon to over-coordination for the construction of structures with electron-deficient bonds. Those nanoclusters form spontaneously by self-assembly in plasmas, do not possess tetrahedral structures, are more stable than any other known SiNCs of this size, and have strong aromatic-like properties due to their high electron delocalization. We demonstrate that non-tetrahedral SiNCs exhibit metallic-like bonding schemes that strongly resemble the one of a homogeneous electron gas in small metal clusters. Standard tetrahedral SiNCs of this size can absorb light only in the ultraviolet, while our calculations have shown that pure, but over-coordinated SiNCs absorb light in the ultraviolet, visible, and infrared spectral region. In this thesis, we present first experimental evidence that supports our theoretical predictions. Using incoherent broadband cavity enhanced absorption spectroscopy, we have measured the absorption of SiNCs, in situ, in a plasma reactor and found that they do absorb light in the visible region. In addition, our absorption measurements in the presence of an applied electric field have provided clear evidence that aromatic SiNCs possess a permanent dipole moment, and we have measured it to be between 2 and 2.5 Debye, in excellent agreement to prior ab initio calculations. Finally, our transmission electron microscopy images of such SiNCs, after their deposition under optimized plasma conditions, have revealed the presence of another exotic form of silicon with a primitive hexagonal structure. Such a structure usually forms after exposing diamond-cubic silicon to extremely high pressures. We tentatively claim that those conditions were, actually, achieved in our experiments due to the “chemistry with a hammer”.In the second part of the thesis, we have undertaken in-depth theoretical and experimental studies on the growth of a new allotropic form of silicon and germanium: a single layer of silicon or germanium atoms, only one atom thick and packed in a hexagonal lattice that closely resembles the lattice of graphene, namely silicene and germanene. In order to rule out any intermixing between silicon or germanium atoms and the underneath substrate atoms, as it was the case for metallic substrates, and to maintain their promising features to be new Dirac materials, we have performed our depositions on a chemically inert graphite substrate. One of our crucial findings is that the silicene or germanene monolayers interact with the graphite substrate via van der Waals forces only. The van der Waals interaction is strong enough to stabilize the deposited monolayers even above room temperature, but weak enough to prevent any hybridization or alloying between silicon or germanium and carbon atoms. Consequently, the outstanding electronic properties of free-standing silicene and germanene, such as Dirac cones and massless electrons, are preserved even after their deposition on graphite surfaces.
• Polarization gating based on Mueller matrices
  
  • Lizana Angel
  • van Eeckhout Albert
  • Adamczyk Kamil
  • Rodríguez Carla
  • Escalera Juan Carlos
  • Garcia-Caurel Enrique
  • Moreno Ignacio
  • Campos Juan
  Journal of Biomedical Optics, Society of Photo-optical Instrumentation Engineers, 2017, 22 (05), pp.1. We present mathematical formulas generalizing polarization gating (PG) techniques. PG refers to a collection of imaging methods based on the combination of different controlled polarization channels. In particular, we show how using the measured Mueller matrix (MM) of a sample, a widespread number of PG configurations can be evaluated just from analytical expressions based on the MM coefficients. We also show the interest of controlling the helicity of the states of polarization used for PG-based metrology, as this parameter has an impact in the image contrast of samples. In addition, we highlight the interest of combining PG techniques with tools of data analysis related to theMM formalism, such as the well-knownMM decompositions. The method discussed in this work is illustrated with the results of polarimetric measurements done on artificial phantoms and real ex-vivo tissues (10.1117/1.JBO.22.5.056004)
  DOI : 10.1117/1.JBO.22.5.056004
• The Role of Oxygen in the Degradation of Methylammonium Lead Trihalide Perovskite Photoactive Layers
  
  • Pellereau Eric
  • Fregnaux Matthieu
  • Dindault Chloé
  • Tondelier Denis
  • Geffroy Bernard
  • Bouree Jean Eric
  • Bourgeteau Tiphaine
  • Lee Heejae
  • Marronnier Arthur
  • Roma Guido
  • Bouttemy Muriel
  • Aureau Damien
  • Vigneron Jacky
  • Steunou Nathalie
  • Etcheberry Arnaud
  • Bonnassieux Yvan
  , 2017. Perovskite materials have already proven their ability to reach photo-electric power conversion efficiencies higher than 22% in appropriate devices. If their instability against time could be solved, they could quickly compete with silicon since they benefit from low-cost manufacturing processes. Our work is dedicated to this stability study using the benefit of X-ray Photoelectron Spectroscopy (XPS) as a main tool, and coupled with XRD and SEM-EDX analysis. Using XPS, it is possible to track the surface (10 nm) changes the perovskite undergoes, in terms of both composition and chemical environments, and is therefore efficient towards understanding the first steps of the degradation process. At first, samples of spin-coated thin-film perovskite without capping on the top (glass/ITO/PEDOT:PSS/MAPI), were aged in different conditions (light with air and vacuum respectively), and analyzed using XPS at different times. The figure below presents the survey spectrum obtained for a fresh sample, and shows that all the expected elements can be identified with this spectrometry method. Starting from an initial known composition, the results obtained reveal interesting changes the material undergoes during the ageing. For example, it was observed that both nitrogen and iodine gradually escape the surface, and also, that metallic lead is observed in the final stages of the degradation process. Then, other currently ongoing experiments are designed to highlight the influence of oxygen and light as previously mentioned , but also to disentangle the influence of the bottom layers on the ageing. This will certainly provide other innovative results on the mechanisms governing the perovskite degradation.
• Fabrication and characterization of evaporated hybrid perovskite based solar cells
  
  • Dindault Chloé
  • Geffroy Bernard
  • Bonnassieux Yvan
  • Tondelier Denis
  , 2017. Over the last years, interest for hybrid perovskite materials as light absorber in photovoltaic devices has increased continuously, from only 14 publications in 2012 to over 2200 in 2016 [1]. Hybrid perovskite deposition techniques can be sort out in two families: wet processing and vacuum deposition. If the first is the most widely used, the second appears more suitable for future commercialization of perovskite solar cells. Indeed, wet processing is highly user dependant and hardly allows homogeneous large surface deposition when vacuum based deposition permits high reproducibility between batches and homogeneity over large area. In this context we report here experimental details to fabricate evaporated hybrid perovskite films including material densities, heating temperatures and deposition rates. The obtained layers will be characterized by absorption spectra, XRD (X-Ray Diffraction) or SEM (Scanning Electron Microscopy). Evaporated hybrid perovskite layers will also be incorporated in photovoltaic devices (structure being ITO/PEDOT:PSS/Perovskite/PCBM/Ag) and characterized by J-V and EQE (External Quantum Efficiency) measurements.
• Anharmonicity in Hybrid and Inorganic Perovskite Materials used for Photovoltaics Applications References
  
  • Marronnier Arthur
  • Lee Heejae
  • Dindault Chloé
  • Tondelier Denis
  • Geffroy Bernard
  • Bourée Jean Eric
  • Bonnassieux Yvan
  • Roma Guido
  , 2017. Hybrid organic-inorganic perovskite materials have emerged over the past five years as absorber layers for new high-efficiency yet low-cost solar cells that combine the advantages of organic and inorganic semiconductors. Despite this sky rocketing evolution, the physics behind the electronic transport in these materials is still poorly understood. Here, employing the linear response (DFPT) approach of Density Functional Theory (DFT) and frozen phonon calculations, we reveal strong anharmonic effects in the inorganic CsPbI$_3$ perovskite structure compared to the hybrid CH$_3$ NH$_3$ PbI$_3$ (MAPbI$_3$) material, and found a double-well instability at the center of the Brillouin Zone. We show that previously reported soft modes are stabilized at the actual lower symmetry equilibrium structure, which occurs in a very flat energy landscape. These findings highlight the crucial role played by temperature in these materials, showing that this perovskite structure can oscillate between two equilibrium states at room temperature. Taking into account these low energy-highly occupied phonon states into the models used for electron-phonon interactions and band gap calculations could lead to a better understanding of the electrical transport properties of perovskite solar cells.
• Modeling of a silane-hydrogen plasma discharge including nanoparticle dynamics for photovoltaic applications.
  
  • Orlac'H Jean-Maxime
  , 2017. This thesis addresses the modeling of silicon nanoparticle dynamics in radio-frequency capacitively-coupled silane plasma discharges for photovoltaic applications.A complete derivation of fluid equations for a two-temperature reactive polyatomic plasma has been achieved in the framework of the kinetic theory of gases. From an asymptotic analysis of the Boltzmann equation, the Chapman-Enskog method was applied to derive the zeroth-order “Euler-type” equations and the first-order “Navier-Stokes-type” equations. Expressions for transport fluxes have been obtained in terms of the macroscopic variables gradients, and associated transport coefficients have been derived.The multicomponent fluid plasma model thus derived has been simplified and implemented numerically in order to model a plasma enhanced chemical vapor deposition reactor as used for silicon thin films deposition. A software has been written in FORTRAN and validated against a benchmark model from the literature. The plasma model has then been applied to typical conditions for low temperature plasma enhanced silicon epitaxy. The main plasma species densities are in good agreement with existing experimental data. The influence of silane plasma chemistry on the DC bias voltage has also been investigated using “tailored voltage” asymmetric waveforms.The model has then been enriched with a sectional model accounting for size and charge of nanoparticles. An estimation of the accommodation coefficient of silane on nanoparticles was obtained from a comparison with existing experimental results. Results of the simulations confirm the critical role of positive ions in the deposition process.The model implemented in this work opens the path for a systematic study of the evolution of the plasma properties as a function of the process conditions and of the influence of nanoparticles on the plasma physicochemical properties.
• Direct Growth of Crystalline Silicon on GaAs by Low Temperature PECVD: Towards Hybrid Tunnel Junctions for III-V/Si Tandem Cells
  
  • Hamon Gwenaëlle
  • Vaissière Nicolas Vaissiere
  • Decobert Jean
  • Lachaume Raphaël
  • Cariou Romain
  • Chen Wanghua
  • Alvarez J
  • Kleider Jean-Paul
  • Roca I Cabarrocas Pere Roca I Cabarrocas
  , 2017.
• Développement d'un colposcope polarimétrique de Müller pour le dépistage du cancer du col utérin : premières mesures in-vivo.
  
  • Deby Stanislas
  , 2017. Cette thèse a été consacrée au développement et à la mise en oeuvre d’un imageur polarimétrique de Müller installé sur un colposcope standard dans le but de diagnostiquer invivo des lésions précancéreuses du col utérin.Ce travail s’est appuyé sur le développement réalisé durant les dix dernières années au LPICM à l'École polytechnique d’une nouvelle technologie d'imagerie médicale non invasive et a priori adaptée à la détection précoce du cancer : l’imagerie polarimétrique.
• Direct Experimental Evidence of Halide Ionic Migration under Bias in CH 3 NH 3 PbI 3−x Cl x ‑Based Perovskite Solar Cells Using GD-OES Analysis
  
  • Lee Heejae
  • Gaiaschi Sofia
  • Chapon Patrick
  • Marronnier Arthur
  • Lee Heeryung
  • Vanel Jean-Charles
  • Tondelier Denis
  • Boureé Jean-Eric
  • Bonnassieux Yvan
  • Geffroy Bernard
  ACS Energy Letters, American Chemical Society, 2017, 2, pp.943 - 949. In recent decades, the development of organic–inorganic hybrid perovskite solar cells (PSCs) has been increasing very quickly due to their high initial efficiency and low-cost process. However, key points such as crystal growth mechanisms, current–voltage hysteresis, and instability remain still unexplained or misunderstood. Among several possibilities, ionic migration in PSCs has been suggested to explain the hysteresis effect. However, direct experimental evidence of ionic migration under operation or measurement conditions of PSCs is still missing. This work shows directly the ionic migration of halogen components (I– and Cl–) of a CH3NH3PbI3–xClx perovskite film under an applied bias using glow discharge optical emission spectrometry (GD-OES). Furthermore, no migration of lead and nitrogen ions is observed on a polarization time scale less than 2 min. The ratio of fixed to mobile iodide ions is deduced from the evolution of the GD-OES profile lines as a function of the applied bias. The average length of iodide and chloride ion migration is deduced from the experimental results. (10.1021/acsenergylett.7b00150)
  DOI : 10.1021/acsenergylett.7b00150
• From Silicon to Germanium Nanowires : growth processes and solar cell structures
  
  • Tang Jian
  , 2017. This thesis is dedicated to develop new solar cell architectures based on nanowires produced by a plasma-assisted Vapor Liquid Solid process. By optical modeling, detailed field and absorption profiles in the NW solar cells have been obtained and a 14 mA/cm2 matched photocurrent has been achieved for a-Si:H/µc-Si:H tandem solar cells. An electrical model for radial PN junction NW solar cells has also been developed from first principle rules, allowing a good understanding of the carrier transport. By analyzing step by step the SiNWs growth in a PECVD system we could propose a detailed explanation for the strong evolution of the NW density, morphology and crystallinity during growth. The rare hexagonal phase of Si has been observed in the as grown SiNWs with diameters smaller than 10 nm. For the first of time, we have provided TEM characterizations from [11-20] direction to give a clear proof of the hexagonal Si phase in as grown SiNWs. To develop low band bap, high mobility material for multi junction NW solar cells, we added germane to silane during the plasma-assisted VLS growth process. Ge contents from 0 to 100% have been achieved with Sn, In and Cu catalysts. We have found that above a critical temperature (~ 350 °C), micrometer long cylindrical Ge NWs can be obtained. NW based PIN radial junction solar cells having a-Si:H, a-SiGe:H and µc-Si:H as intrinsic absorber layers have been fabricated. For the SiGeNWs based solar cells, a 6% energy conversion efficiency has been achieved with p-i-n configuration. To our knowledge, this is the first demonstration of SiGeNWs based photovoltaic device.
• Spirobifluorene Regioisomerism: A Structure–Property Relationship Study
  
  • Sicard Lambert
  • Quinton Cassandre
  • Peltier Jean-David
  • Tondelier Denis
  • Geffroy Bernard
  • Biapo Urelle
  • Métivier Rémi
  • Jeannin Olivier
  • Rault-Berthelot Joëlle
  • Poriel Cyril
  • Thiery Sébastien
  Chemistry - A European Journal, Wiley-VCH Verlag, 2017, 23 (32), pp.7719-7727. The present works report the first structure–prop-erty relationship study of a key class of organic semiconductors , that is, the four spirobifluorene positional isomers possessing a para-, meta-or ortho-linkage. The remarkable and surprising impact of the ring bridging and of the linkages on the electronic properties of the regioisomers has been particularly highlighted and rationalised. The impact of the ring bridging on the photophysical properties has been stressed with notably the different influence of the linkages and the bridge on the singlet and triplet excited states. The first member of a new family of spirobifluorenes substituted in the 1-position, which presents better performance in blue phosphorescent OLEDs than those of its regioisomers, is reported. These features highlight not only the great potential of 1-substituted spirobifluorenes, but also the remarkable impact of regioisomerism on electronic properties. (10.1002/chem.201700570)
  DOI : 10.1002/chem.201700570
• Influence of deposition rate on the structural properties of plasma-enhanced CVD epitaxial silicon
  
  • Chen Wanghua
  • Cariou Romain
  • Hamon Gwenaëlle
  • Léal Ronan
  • Maurice Jean-Luc
  • Cabarrocas Pere Roca I
  Scientific Reports, Nature Publishing Group, 2017, 7 (1). (10.1038/srep43968)
  DOI : 10.1038/srep43968