Publications

2016

• Graphitization and amorphization of textured carbon using high-energy nanosecond laser pulses
  
  • Loisel Loïc
  • Châtelet Marc
  • Giudicelli Guillaume
  • Lebihain Mathias
  • Yang Yi
  • Cojocaru Costel-Sorin
  • Constantinescu Andrei
  • Tay Beng Kang
  • Lebental Bérengère
  Carbon, Elsevier, 2016, 105, pp.227-232. Laser pulses can effectively induce local structural changes and modify the physical properties of carbon allotropes. So far, only graphitization has been demonstrated using low laser energies (≤1 J/cm2). The novelty of this paper is a result of laser-induced amorphization of a highly anisotropic carbon allotrope by using high energy (1.5–15.4 J/cm2) 5 ns, 532 nm Nd-YAG laser pulses. Moreover, cycling phase change, between an amorphous and a crystalline phase, is also obtained by adjusting the pulse energy. However, cycling ability is restricted to a few cycles as a consequence of laser-induced surface damages caused by both high temperatures during and high thermal gradients during and after laser exposure. The occurrence of graphitization or amorphization depends on the amount of solid crystalline seeds during solidification from the melt, which is controlled by the post-pulse temperature of the carbon surface. This study uncovers new applications of carbon allotropes, such as optically-controlled reversible phase-change memories. (10.1016/j.carbon.2016.04.026)
  DOI : 10.1016/j.carbon.2016.04.026
• Modeling of Mueller Matrix Response from Diffracting Structures
  
  • Kohut K
  • Postava K
  • Mrazkova M
  • Foldyna M
  • Cabarrocas P. Roca I
  • Mičica M
  • Pištora J
  Journal of Nanoscience and Nanotechnology, American Scientific Publishers, 2016, 16 (8), pp.7805 - 7809. (10.1166/jnn.2016.12553)
  DOI : 10.1166/jnn.2016.12553
• Noble metal-free hydrogen-evolving photocathodes based on small molecule organic semiconductors
  
  • Morozan Adina
  • Bourgeteau Tiphaine
  • Tondelier Denis
  • Geffroy Bernard
  • Jousselme Bruno
  • Artero Vincent
  Nanotechnology, Institute of Physics, 2016, 27 (35), pp.355401. Organic semiconductors have great potential for producing hydrogen in a sustainable and economically-viable manner because they rely on readily available materials with highly tunable properties. We demonstrate here the relevance of heterojunctions to the construction of H2-evolving photocathodes, exclusively based on earth-abundant elements. Boron subnaphthalocyanine chloride proved a very promising acceptor in that perspective. It absorbs a part of the solar spectrum complementary to α-sexithiophene as a donor, thus generating large photocurrents and providing a record onset potential for light-driven H2 evolution under acidic aqueous conditions using a nanoparticulate amorphous molybdenum sulfide catalyst. (10.1088/0957-4484/27/35/355401)
  DOI : 10.1088/0957-4484/27/35/355401
• Geometric and chemical components of the giant piezoresistance in silicon nanowires
  
  • Mcclarty M.
  • Jegenyes N.
  • Gaudet M.
  • Toccafondi C.
  • Ossikovski R.
  • Vaurette Francois
  • Arscott S.
  • Rowe A.
  Applied Physics Letters, American Institute of Physics, 2016, 109 (2), pp.023102. (10.1063/1.4955403)
  DOI : 10.1063/1.4955403
• Hybrid kinetic/fluid modeling of silicon nanoparticles dynamics in silane plasma discharges
  
  • Orlac’h J.-M.
  • Giovangigli V.
  • Novikova T.
  • Cabarrocas P. Roca I
  , 2016, pp.130004. (10.1063/1.4967630)
  DOI : 10.1063/1.4967630
• Zinc oxide as a hole blocking layer for perovskite solar cells deposited in atmospheric conditions
  
  • Hadouchi Warda
  • Rousset Jean
  • Tondelier Denis
  • Geffroy Bernard
  • Bonnassieux Yvan
  RSC Advances, Royal Society of Chemistry, 2016, 6 (72), pp.67715-67723. be Zinc oxide (ZnO) is a widely used transparent conductive oxide owing to its tunable optoelectronic properties, particularly in the field of solar energy conversion. In this study a thin layer of this compound has been employed as a hole-blocking layer in a planar perovskite based solar cell in substitution for the classical titanium dioxide (TiO 2) bilayer. The introduction of intrinsic ZnO between the perovskite layer and the degenerate n-type doped contact leads to a large reduction of the recombination at this interface. Optimization of the ZnO layer properties together with that of the perovskite deposition parameters leads to the measurement of a power conversion efficiency of 14.2% measured at a reverse scan on a 0.175 cm 2 cell. Moreover, the ageing cell performance has been investigated over more than two months for both encapsulated and non-encapsulated devices. When a decrease of the fill factor with time, possibly related to the degradation of the cell contact, is observed, the short circuit current (>18 mA cm À2) and the open circuit (>1 V) potential remain remarkably constant. (10.1039/c6ra16865e)
  DOI : 10.1039/c6ra16865e
• OLED for display and lighting applications: current issues and future directions
  
  • Geffroy Bernard
  , 2016. Organic Electronics have received a lot of attention during the last years and advancements are leading to commercial products. Organic Light-Emitting Diodes (OLEDs) have already entered the mass production market in small size displays (smart phones, ...) or larger area display devices for OLEDtelevisions. However, the request in the market continues to grow for low-power, low-cost and flexible devices. OLEDs have also shown a great potential for lighting applications and worldwide research is ongoing to create high-brightness, high efficiency and long life white OLEDs for lighting. This presentation will give an introduction to OLED operation mechanisms and review recent insights into OLEDs materials, device structures and manufacturing processes. Some recent results from our group on the use of new host materials and TADF emitters will be presented.
• Optimization and optical characterization of vertical nanowire arrays for core-shell structure solar cells
  
  • Foldyna Martin
  • Togonal Alienor Svietlana
  • Roca I Cabarrocas Pere
  • Rusli Rusli
  Solar Energy Materials and Solar Cells, Elsevier, 2016, 159, pp.640 - 648. (10.1016/j.solmat.2016.06.014)
  DOI : 10.1016/j.solmat.2016.06.014
• Ex vivo Mueller polarimetric imaging of the uterine cervix: a first statistical evaluation
  
  • Rehbinder Jean
  • Haddad Huda
  • Deby Stanislas
  • Teig Benjamin
  • Nazac André
  • Novikova Tatiana
  • Pierangelo Angelo
  • Moreau François
  Journal of Biomedical Optics, Society of Photo-optical Instrumentation Engineers, 2016, 21 (7), pp.071113.
• Special Section Guest Editorial: Polarized Light for Biomedical Applications
  
  • Novikova Tatiana
  • Meglinski Igor
  • Ramella-Roman Jessica
  • Tuchin Valery
  Journal of Biomedical Optics, Society of Photo-optical Instrumentation Engineers, 2016, 21 (7), pp.071001. (10.1117/1.JBO.21.7.071001)
  DOI : 10.1117/1.JBO.21.7.071001
• Special Section Guest Editorial: Polarized Light for Biomedical Applications
  
  • Novikova Tatiana
  • Meglinski Igor
  • Ramella-Roman Jessica
  • Tuchin Valery
  Journal of Biomedical Optics, Society of Photo-optical Instrumentation Engineers, 2016, 21 (7), pp.071001. (10.1117/1.JBO.21.7.071001)
  DOI : 10.1117/1.JBO.21.7.071001
• Wide range local resistance imaging on fragile materials by conducting probe atomic force microscopy in intermittent contact mode
  
  • Vecchiola Aymeric
  • Chrétien Pascal
  • Delprat Sophie
  • Bouzehouane Karim
  • Schneegans Olivier
  • Seneor Pierre
  • Mattana Richard
  • Tatay Sergio
  • Geffroy Bernard
  • Bonnassieux Yvan
  • Mencaraglia Denis
  • Houzé Frédéric
  Applied Physics Letters, American Institute of Physics, 2016, 108, pp.243101. An imaging technique associating a slowly intermittent contact mode of atomic force microscopy (AFM) with a home-made multi-purpose resistance sensing device is presented. It aims at extending the widespread resistance measurements classically operated in contact mode AFM to broaden their application fields to soft materials (molecular electronics, biology) and fragile or weakly anchored nano-objects, for which nanoscale electrical characterization is highly demanded and often proves to be a challenging task in contact mode. Compared with the state of the art concerning less aggressive solutions for AFM electrical imaging, our technique brings a significantly wider range of resistance measurement (over 10 decades) without any manual switching, which is a major advantage for the characterization of materials with large on-sample resistance variations. After describing the basics of the set-up, we report on preliminary investigations focused on academic samples of self-assembled monolayers with various thicknesses as a demonstrator of the imaging capabilities of our instrument, from qualitative and semi-quantitative viewpoints. Then two application examples are presented, regarding an organic photovoltaic thin film and an array of individual vertical carbon nanotubes. Both attest the relevance of the technique for the control and optimization of technological processes (10.1063/1.4953870)
  DOI : 10.1063/1.4953870
• Modulation of the Physicochemical Properties of Donor–Spiro–Acceptor Derivatives through Donor Unit Planarisation: Phenylacridine versus Indoloacridine. New Hosts for Green and Blue Phosphorescent Organic Light-Emitting Diodes (PhOLEDs)
  
  • Thierry Sébastien
  • Tondelier Denis
  • Geffroy Bernard
  • Jeannin Olivier
  • Rault-Berthelot Joelle
  • Poriel Cyril
  Chemistry - A European Journal, Wiley-VCH Verlag, 2016, 22 (29), pp.10136-10149. This work reports a detailed structure–property relationship study of a series of efficient host materials based on the donor–spiro–acceptor (D-spiro-A) design for green and sky-blue phosphorescent organic light-emitting diodes (PhOLEDs). The electronic and physical effects of the indoloacridine (IA) fragment connected through a spiro bridge to different acceptor units, namely, fluorene, dioxothioxanthene or diazafluorene moiety, have been investigated in depth. The resulting host materials have been easily synthesised through short, efficient, low-cost, and highly adaptable synthetic routes by using common intermediates. The dyes possess a very high triplet energy (ET) and tuneable HOMO/LUMO levels, depending on the strength of the donor/acceptor combination. The peculiar electrochemical and optical properties of the IA moiety have been investigated though a fine comparison with their phenylacridine counterparts to study the influence of planarisation. Finally, these molecules have been incorporated as hosts in green and sky-blue PhOLEDs. For the derivative SIA-TXO2 as a host, external quantum efficiencies as high as 23 and 14 % have been obtained for green and sky-blue PhOLEDs, respectively. (10.1002/chem.201600652)
  DOI : 10.1002/chem.201600652
• All-Solution-Processed Organic Light-Emitting Diodes Based on Photostable Photo-cross-linkable Fluorescent Small Molecules
  
  • Derue Lionel
  • Olivier Simon
  • Tondelier Denis
  • Maindron Tony
  • Geffroy Bernard
  • Ishow Eléna
  ACS Applied Materials & Interfaces, Washington, D.C. : American Chemical Society, 2016, 8, pp.16207-16217. We demonstrate herein the fabrication of small molecule-based OLEDs where four organic layers from the hole-to the electron-transporting layers have successively been deposited by using an all-solution process. The key feature of the device relies on a novel photopolymerizable red-emitting material, made of small fluorophores substituted with two acrylate units, and displaying high-quality film-forming properties as well as high emission quantum yield as nondoped thin films. Insoluble emissive layers were obtained upon UV irradiation using low illumination doses, with no further need of postcuring. Very low photodegradation was noticed, giving rise to bright layers with a remarkable surface quality, characterized by a mean RMS roughness as low as 0.7 nm after development. Comparative experiments between solution-processed OLEDs and vacuum-processed OLEDs made of fluorophores with close architectures show external quantum efficiencies in the same range while displaying distinct behaviors in terms of current and power efficiencies. They validate the proof of concept of nondoped solution-processable emissive layers exclusively made of photopolymerized fluorophores, thereby reducing the amount of components and opening the way toward cost-effective fabrication of solution-processed OLED multilayer architectures. (10.1021/acsami.6b05197)
  DOI : 10.1021/acsami.6b05197
• Direct growth of crystalline Silicon on GaAs by Low Temperature PECVD: toward hybrid tunnel junctions for III-V/Si tandem cells
  
  • Hamon Gwenaëlle
  • Decobert Jean
  • Vaissiere N.
  • Lachaume Raphaël
  • Cariou Romain
  • Chen Wanghua
  • Alvarez José
  • Habka Nada
  • Kleider Jean-Paul
  • Cabarrocas Pere Roca I.
  , 2016.
• Silicon nano-trees as high areal capacity anodes for lithium-ion batteries
  
  • Leveau Lucie
  • Laïk Barbara
  • Pereira-Ramos Jean Pierre
  • Gohier Aurelien
  • Tran-Van Pierre
  • Cojocaru Costel-Sorin
  Journal of Power Sources, Elsevier, 2016, 316, pp.1-7. (10.1016/j.jpowsour.2016.03.053)
  DOI : 10.1016/j.jpowsour.2016.03.053
• Caracterisation de tissus biologiques par polarimetrie de mueller à travers une fibre optique endoscopique
  
  • Vizet Jérémy
  • Manhas Sandeep
  • Tran Jacqueline
  • Validire P.
  • Benali Abdallah
  • Garcia-Caurel Enric
  • Pierangelo Angelo
  • de Martino Antonello
  • Pagnoux Dominique
  , 2016.
• Aging of Solution processed perovskite solar cells
  
  • Lee Heejae
  • Marronnier Arthur
  • Tondelier Denis
  • Tusseau-Nenez Sandrine
  • Bonassieux Yvan
  • Geffroy Bernard
  , 2016. In recent years, perovskite (CH3NH3PbI3-XClX) solar cells have been studied steadily due to their potential properties: low-cost processing and possibility to produce large area by low temperature processes. The perovskite film used as light absorber is obtained by solution process and has a crystalline structure. Many different solvents are being developed and gradually adopted for high-performance inorganic-organic hybrid perovskite solar cells. PEDOT:PSS and PC60BM are used as hole transport layer (HTL) and electron transport layer (ETL), respectively. The size of active area is 0.28cm 2. In this study, 9.54% of power conversion efficiency (PCE) is obtained with a saturated current density (Jsc) of 15.03 mA/cm 2. The degradation of the performance of the solar cell is studied with XRD measurements as well as electrical characterizations. The perovskite solar cell performance decreases with aging time (Table 1 and Figure 1a) and XRD data show the growing of the PbI2 peak and a decreasing of the CH3NH3PbI3 (MAPbI3) peak.
• Study of different hole transporting materials for hybrid perovskite solar cells
  
  • Dindault Chloé
  • Dalinot Clément
  • Tondelier Denis
  • Leriche Philippe
  • Bonnassieux Yvan
  • Geffroy Bernard
  , 2016. Over the last years, interest for organolead trihalide perovskite materials (ABX3 where A is an ammonium cation, B a metal cation and X an halide) as light absorber in solar cells has increased continuously [1]. One of the most studied hybrid perovskite material is methylammonium lead triiodide (MAPbI3) leading to 15 to 20% efficiencies in a FTO/TiO2/mp-TiO2/MAPbI3/Au structure [2,3]. A new method for preparation and one-step process deposition of the perovskite material [4] is here used in a planar heterojunction FTO/compact-TiO2/MAPbI3/HTM/Au structure leading to 11% efficiency (on 0.28 cm² cell) when Spiro-MeOTAD is used as HTM (J/V curve Figure 1 (left)). Five new spiro-based HTM (Figure 1 (right)) are then compared to this reference system.
• Elucidating Methylamonium and Cesium based Hybrid Perovskites' Dielectric Properties using Ab Initio Calculations and Ellipsometry Measurements
  
  • Marronnier Arthur
  • Lee Heejae
  • Tondelier Denis
  • Geffroy Bernard
  • Bourée Jean-Eric
  • Roma Guido
  • Bonnassieux Yvan
  , 2016. Methylamonium lead halide 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. Similar to inorganic semiconductors, hybrid perovskites (mostly CH3NH3PbI3 and more recently cesium-based) have shown low exciton binding energies 1 (≈ 5-30 meV) indicating a potentially high value (≈ 70) at low frequencies for their relative dielectric constant. Others studies have even found giant values (≈ 1000 in the dark) for the dielectric constant 2 at very low frequencies (<1 Hz). Understanding the excitons' physics in these materials is crucial in order to increase the charge extraction and improve the solar cells' efficiency. Here, we study the phonon modes and dielectric properties of both methylamonium (CH3NH3PbI3) and cesium (CsPbI3) lead iodide perovskite structures using DFT (Density Functional Theory) calculations. Phonon frequencies for both the cubic (T>600K) and orthorhombic (T<530K) phases of CsPbI3 are derived using the linear response approach (DFPT). As for the orthorhombic phase (figure 1), we find that CsPbI3 shows a very flat energy profile around its equilibrium structure (figure 2). We derive the dielectric matrix in the high frequency regime (> 1 THz) from the linear response and aim to extract the low frequency dielectric constant from the phonon frequency splitting between normal and longitudinal modes. The results are expected to determine the possibility of a giant dielectric constant for these hybrid perovskites. The dielectric properties obtained for CH3NH3PbI3 are being compared to ellipsometry measurements performed in collaboration with Horiba Jobin Yvon company.
• Low temperature plasma enhanced CVD epitaxial growth of silicon on GaAs: a new paradigm for III-V/Si integration
  
  • Cariou Romain
  • Chen Wanghua
  • Maurice Jean-Luc
  • Yu Jingwen
  • Patriarche Gilles
  • Mauguin Olivia
  • Largeau Ludovic
  • Decobert Jean
  • Roca I Cabarrocas Pere
  Scientific Reports, Nature Publishing Group, 2016, 6 (1). The integration of III-V semiconductors with silicon is a key issue for photonics, microelectronics and photovoltaics. With the standard approach, namely the epitaxial growth of III-V on silicon, thick and complex buffer layers are required to limit the crystalline defects caused by the interface polarity issues, the thermal expansion, and lattice mismatches. To overcome these problems, we have developed a reverse and innovative approach to combine III-V and silicon: the straightforward epitaxial growth of silicon on GaAs at low temperature by plasma enhanced CVD (PECVD). Indeed we show that both GaAs surface cleaning by SiF4 plasma and subsequent epitaxial growth from SiH4/H2 precursors can be achieved at 175 °C. The GaAs native oxide etching is monitored with in-situ spectroscopic ellipsometry and Raman spectroscopy is used to assess the epitaxial silicon quality. We found that SiH4 dilution in hydrogen during deposition controls the layer structure: the epitaxial growth happens for deposition conditions at the transition between the microcrystalline and amorphous growth regimes. SIMS and STEM-HAADF bring evidences for the interface chemical sharpness. Together, TEM and XRD analysis demonstrate that PECVD enables the growth of high quality relaxed single crystal silicon on GaAs. (10.1038/srep25674)
  DOI : 10.1038/srep25674
• In-Depth Analysis of III-V/Epi-SiGe Tandem Solar Cell Performance Including Advanced Light Trapping Schemes
  
  • Lachaume Raphaël
  • Foldyna Martin
  • Hamon Gwenaëlle
  • Decobert Jean
  • Cariou Romain
  • Cabarrocas Pere Roca I.
  • Alvarez José
  • Kleider Jean-Paul
  , 2016. The growing interest in new concepts of III-V/Si tandem solar cells arises from the need to reduce the cost of high efficiency III-V based multi-junctions by using low cost substrates such as silicon. Because it is still a challenge to grow III-V materials directly onto Si wafers due to thermal expansion and lattice mismatch issues, other ways of combining III-V compounds and Si have been developed. Among them is the reversed metamorphic concept recently proposed by Cariou et al.. In the latter approach, the Si bottom cell is deposited by low temperature PECVD (<200°C) directly on the III-V top-cell, preventing the degradation of the electrical properties of the underlying III-V layers grown by MOVPE. Though the possibility to obtain a high crystalline quality for the epitaxial silicon or silicon-germanium alloys has already been demonstrated by the same authors, precise evaluations of both the electrical properties of the epi-Si absorber and the overall performance of such a tandem cell are mandatory. For this purpose, in this work we propose an in-depth electrical and optical analysis of the potential of this concept in terms of efficiency by means of simulations and characterization.
• Charge Transport and Contact Resistance in Coplanar Devices Based on Colloidal Polyaniline Dispersion
  
  • Masillamani Appan Merari
  • Perinka Nikola
  • Hajna Milena
  • Stejskal Jaroslav
  • Tondelier Denis
  • Bonnassieux Yvan
  • Vanel Jean-Charles
  • Geffroy Bernard
  • Mencaraglia Denis
  Journal of Polymer Science Part B: Polymer Physics, Wiley, 2016, 54, pp.1710-1716. The charge transport properties of thin films prepared from colloidal dispersion of polyaniline stabilized by poly(N-vinylpyrrolidone) (PANI/PVP) have been investigated. The electrical characterization of coplanar device comprising of gold electrodes and PANI/PVP film deposited by spin coating served to gain insights into the contact and bulk resistance. The films prepared from PANI/PVP colloidal dispersion show high stability over a large temperature range. Temperature dependent measurements in the range from 90 to 350 K reveal that the charge transport can be described by a three-dimensional variable-range hopping mechanism as the dominant mode in the films. The stability of the films cast from dispersion within a large temperature range opens the possibility of the application as a polymer semiconductor layer in sensors and charge-transport interlayer in organic solar cells. (10.1002/polb.24074)
  DOI : 10.1002/polb.24074
• Study of Electronic Properties of Hydrogenated Amorphous Silicon Thin Film from SiH4/H2 using Tailored Voltage Waveforms
  
  • Wang Junkang
  • Ventosinos Federico
  • Longeaud Christophe
  • Bruneau Bastien
  • Daineka D.
  • Elyaakoubi Mustapha
  • Stephanos E.
  • Kleider Jean-Paul
  • Johnson Erik
  , 2016.
• Silicon Nanowires for Photovoltaics : from the Material to the Device
  
  • Togonal Alienor
  , 2016. Silicon Nanowire (SiNW) based solar cells offer an interesting choice towards low-cost and highly efficient solar cells. Indeed solar cells based on SiNWs benefit from their outstanding optical properties such as extreme light trapping and very low reflectance. In this research project, we have fabricated disordered SiNWs using a low-cost top-down approach named the Metal-Assisted-Chemical-Etching process (MACE). The MACE process was first optimized to reduce the strong agglomeration observed at the top-end of the SiNWs by tuning the wettability properties of both the initial substrate and the SiNWs surface. By combining the MACE process with the nanosphere lithography, we have also produced ordered SiNW arrays with an accurate control over the pitch, diameter and length. The optical properties of these SiNW arrays were then investigated both theoretically and experimentally in order to identify the geometrical configuration giving the best optical performance. Disordered and ordered SiNW arrays have been integrated into two types of solar cells: heterojunction with intrinsic thin layer (HIT) and hybrid devices. SiNW based HIT devices were fabricated by RF-PECVD and the optimization of the process conditions has allowed us to reach efficiency as high as 12.9% with excellent fill factor above 80%. Hybrid solar cells based on the combination of SiNWs with an organic layer have also been studied and characterized. The possible transfer of this concept to the thin film technology is finally explored.