Alberto Salleo Stanford University
Ana Claudia Arias Palo Alto Research Center, Inc.
Dean M. DeLongchamp National Institute of Standards and Technology
Cherie R. Kagan University of Pennsylvania
G1: Conformal Macroelectronics
Monday PM, December 01, 2008
Room 207 (Hynes)
9:30 AM - **G1.1
Single Crystalline Inorganic Semiconductors for Unusual Format Electronics.
John Rogers 1 Show Abstract
1 Materials Science and Engineering, University of Illinois-Urbana Champaign, Urbana, Illinois, United States
10:00 AM - G1.2
High Throughput Transfer Printing of Large Scale Chemically Derived Graphene.
Matthew Allen 1 2 3 , Vincent Tung 2 3 , Richard Kaner 1 2 3 , Yang Yang 2 3 Show Abstract
1 Chemistry and Biochemistry, UCLA, Los Angeles, California, United States, 2 , California NanoSystem Institute, Los Angeles, California, United States, 3 Materials Science and engineering, UCLA, Los Angeles, California, United States
Single layer graphene has attracted intense research interest since its discovery in 2003. However, difficulties in producing single layer specimens have encouraged the development of chemical routes. One such method is the oxidation, exfoliation, and subsequent reduction of graphite oxide through solution processing. Although graphite oxide produced specimens have been used to fabricate electrical devices, wafer scale processing has not yet been achieved due to the inability of registration in well-defined locations. Here we report a transfer printing process that allows for precise patterning of chemically derived graphene. Utilizing a polydimethylsiloxane (PDMS) stamp and the manipulation of surface energies, we successfully transfer spin-coated materials from one substrate to another. The method is capable of transferring sharp features to precise locations as confirmed by Raman mapping. This represents the first large scale, high throughput transfer printing of graphene and paves the way for future complementary circuit design.
10:15 AM - G1.3
Yarn-like Devices for Smart Wearable Electronics.
Piero Cosseddu 1 2 , Giorgio Mattana 1 2 , Gianluca Atzeni 1 , Magdalena Cybula 3 , Izabela Kruscinska 3 , Annalisa Bonfiglio 1 2 Show Abstract
1 Dept. of Electrical and Electronic Engineering, University of Cagliari, Cagliari Italy, 2 S3 nanoStructures and bioSystems at Surfaces, CNR-INFM, Modena Italy, 3 3Technical University of Lodz, 3Technical University of Lodz, Lodz Poland
Organic materials are becoming of great appeal also in the field of e-textiles, as they show an interesting combination of electronic and mechanical properties that can be favourably exploited in smart textiles.We present an example of organic field effect transistor (OFET) characterized by textile process fully compatible size and geometry. The devices have been obtained starting from a cylindrical metal fibre with typical diameters ranging around 45-60 µm, acting as the gate electrode, covered by a uniform insulating layers (polymide, and polypyrrole in the undoped state), which acts as the gate dielectric for the final device. As a result, this yarn is very flexible and can be employed, alone or twisted to another fibre, in textile processes.Different organic semiconductors were tested as the active layer forming the channel of the final device, and were deposited directly on the bare insulating yarn surface, while source and drain electrodes were realized afterwards in order to obtain a top contact configuration. AFM and SEM measurements demonstrated that both the dielectric and the organic semiconductor layers were uniformly deposited on the structure allowing to obtain well performing devices.When pentacene was used as organic semiconductor we obtained high performances unipolar p-type OFETs with an average hole mobility very close to 0.1 cm^2/Vs, and Ion/Ioff up to 10^4. In this paper we will show also how, thanks to the flexibility of the final structure, these devices can be employed as deformation sensors, as the output current varies reproducibly by applying a mechanical stimulus to the whole structure.Moreover, we will show how, using a double layer structure as active layer, employing pentacene/C60 heterojunction, it was possible to obtain ambipolar OFETs devices with very good mobility, up to 3x10^-2cm^2/Vs and 1.5x10^-2cm^2/Vs for the p- and n-type regime respectively. This was possible thanks to the improvements of the C60 layer structural and morphological characteristics, as supported by AFM and XRD characterization, which allowed, even by using high work function metals (Cu, Au and PEDOT:PSS) for the realization of the source and drain electrodes, to obtain a very efficient electron injection into the channel. These findings are very important because demonstrate the possibility of realizing organic complementary circuits by using very thin yarns suitable to be employed into a textile process. We will show our first preliminary attempts on the realization of complementary inverters by using the reported technology, which paves the way for the easy realization of smart wearable electronics.
10:30 AM - G1.4
Sintering Metal Nanoparticles.
Howard Wang 1 Show Abstract
1 Department of Mechanical Engineering, Binghamton University, SUNY, Binghamton, New York, United States
10:45 AM - G1.5
A Hemispherical Electronic Eye Camera Based on Compressible Silicon Optoelectronics.
Heung Cho Ko 1 , Mark Stoykovich 1 , Jizhou Song 2 , Viktor Malyarchuk 3 , Won Mook Choi 1 , Chang-Jae Yu 1 , Joseph Geddes 4 , Jianliang Xiao 5 , Shuodao Wang 5 , Yonggang Huang 5 6 , John Rogers 1 2 3 Show Abstract
1 Department of Materials Science and Engineering , University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 2 Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 3 Frederick-Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 4 Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 5 Department of Mechanical Engineering, Northwestern University, Evanston, Illinois, United States, 6 Department of Civil and Environmental Engineering, Northwestern University, Evanston, Illinois, United States
The human eye represents a remarkable imaging device, with many attractive design features. Prominent among these is a hemispherical detector geometry, similar to that found in many other biological systems, that enables wide field of view and low aberrations with simple, few component, imaging optics. This type of configuration is extremely difficult to achieve using established optoelectronics technologies, due to the intrinsically planar nature of the patterning, deposition, etching, materials growth and doping methods that exist for fabricating such systems. In this study, we introduce a route to curvilinear optoelectronics and electronic eye imagers that begins with well established electronic materials and planar processing approaches to create optoelectronic systems on flat, two dimensional surfaces, in unusual designs that allow full compressibility/stretchability to large levels of strain (~50% or more). This feature enables planar layouts to be geometrically transformed (i.e. conformally wrapped) to nearly arbitrary curvilinear shapes. In the example presented here, we use a hemispherical, elastomeric transfer element to accomplish this transformation with an electrically interconnected array of single crystalline silicon photodiodes and current blocking p-n junction diodes assembled in a passive matrix layout. The resulting hemispherical focal plane arrays, when combined with imaging optics and hemispherical housings, yield electronic cameras that have overall sizes and shapes comparable to the human eye. In a general sense, these methods, taken together with our theoretical analyses of their associated mechanics, provide practical routes for integrating well developed planar device technologies onto the surfaces of complex curvilinear objects, suitable for diverse applications that cannot be addressed using conventional means. Reference: Ko, H. C.; Stoykovich, M. P.; Song, J.; Malyarchuk, V.; Choi, W. M.; Yu, C.-J.; Geddes III, J.; Xiao, J.; Wang, S.; Huang, Y.; Rogers, J. A., Nature, in press.
11:00 AM - G1: Conformal
G2: Macroelectronics on Flexible Substrates
Monday PM, December 01, 2008
Room 207 (Hynes)
11:30 AM - **G2.1
Roll-to-Roll Manufacturing of Electronics on Flexible Substrates using Self-Aligned Imprint Lithography.
Ohseung Kwon 1 , Marcia Almanza-Workman 1 , Alison Chaiken 1 , Robert Cobene 1 , Robert Garcia 1 , Warren Jackson 1 , Mehrban Jam 1 , Albert Jeans 1 , Kim Han-Jun 1 , Hao Luo 1 , Ping Mei 1 , Craig Perlov 1 , Carl Taussig 1 , Frank Jeffrey 2 , Steve Braymen 2 , Don Larson 2 , Jason Hauschildt 2 Show Abstract
1 , HP Laboratories, Palo Alto, California, United States, 2 , Power Film Solar Inc., Ames, Iowa, United States
12:00 PM - G2.2
Influence of Mechanical Deformation on the Electrical Performance of OTFTs.
Piero Cosseddu 1 2 , Emanuele Orgiu 1 2 , Ileana Manunza 1 2 , Francesco Arca 1 , Gabriele Cocco 1 , Andrea Spanu 1 , Annalisa Bonfiglio 1 2 Show Abstract
1 Dept. of Electrical and Electronic Engineering, University of Cagliari, Cagliari Italy, 2 S3 nanoStructures and bioSystems at Surfaces, CNR-INFM, Modena Italy
Here we propose fully flexible organic field effect transistors (OFETs) assembled on plastic films as sensors for physiological parameters monitoring. Starting from a highly flexible and free standing OFET structure, realized using a very thin PET foil (1.4 um thick) acting at the same time as gate dielectric and as flexible mechanical support for the whole structure, we realized mechanical sensors in which a sharp and reversible sensitivity of the device output current to an elastic deformation, induced by means of a mechanical stimulus on the device channel, is observed. A careful analysis of the output current dependence from the applied pressure shows that this phenomenon might depend on the induced mobility, threshold voltage, trap states and contact resistances variation due to morphological and structural changes taking place within the semiconductor layer upon mechanical stimulus application.In order to have a deeper understanding of the physical causes dominating this behavior, we also present a preliminary investigation on the effective correlation between sensitivity and morphological/interfacial properties of both different organic semiconductor films (employed as active/sensitive layers) and polymeric dielectrics (whose interface with different polymers/semiconductor gives place to different electrical behavior).We realized OFET based mechanical sensors employing different organic semiconductors, namely small molecules (pentacene) deposited by thermal evaporation and different polymers (P3HT and pentacene TIPS) which can be deposited either by spin coating or drop casting, usually leading to organic films with very different morphological and structural characteristics. At the same time several flexible polymeric gate insulators have been tested in order to evaluate the different interfacial trap states dependence on mechanical stimuli. As a result, these films are expected to give rise to very different material-dependent sensitivity.Due to its high flexibility the proposed structures can be applied to any kind of substrate, fabric and/or 3D structure so opening the way for a wide range of possible applications. In this talk we will show how such a configuration can be used for monitoring different physiological parameters, as human posture by using a matrix of sensors embedded into a sole shoe, and human breathing rate by applying the same structure to wearable elastic bends placed around the diaphragm area.Thanks to the flexibility and low cost processing employed technique our devices pave the way for the realization of flexible arrays or matrixes of sensors to be employed in a wide range of innovative applications, such as sensorized clothes for physiological parameter detection, or in robotics for the realization of artificial “robot skin”.I. Manunza et al., Biosensors and Bioelectronics 22, 2775-2779, (2007)A. Bonfiglio,et al., Proc. SPIE Photonics 2007, S. Diego (USA) 26-31, August 2007
12:15 PM - G2.3
A Novel Hybrid Inorganic-polymeric Permeation Barrier for Flexible Displays.
Prashant Mandlik 1 , Lin Han 1 , Jonathan Gartside 1 , I-Chun Cheng 3 , Sigurd Wagner 1 , Jeff Silvernail 2 , Rui-Qing Ma 2 , Mike Hack 2 , Julie Brown 2 Show Abstract
1 , Princeton University, Princeton, New Jersey, United States, 3 , National Taiwan University, Taipei Taiwan, 2 , Universal Display Corporation, Ewing, New Jersey, United States
Monday, 12/1New Presentation Time/Paper NumberG2.4 @ 11:30 AM to G2.3 @ 11:15 AMA Novel Hybrid Inorganic-polymeric Permeation Barrier for Flexible Displays. Prashant Mandlik
12:30 PM - G2.4
Formation of Solution Processable Organic Composites with Functionalized Carbon Naotubes for OTFTs.
Silvia Janietz 1 , Tatjana Egorov-Brening 1 , Bjoern Gruber 1 Show Abstract
1 Polymer Electronics, FhG-IAP, Potsdam, Brandenburg, Germany
Monday, 12/1New Presentation Time/Paper NumberG2.5 @ 11:45 AM to G2.4 @ 11:30 AMFormation of Solution Processable Organic Composites with Functionalized Carbon Naotubes for OTFTs. Silvia Janietz
12:45 PM - G2.5
Three Dimensional Patterning of Indium Tin Oxide and Its Application to Hemispherical Organic Focal Plane Arrays.
Xin Xu 1 2 , Momchil Mihnev 3 , Andre Taylor 5 , Stephen Forrest 2 3 4 Show Abstract
1 Electrical Engineering, Princeton University, Princeton, New Jersey, United States, 2 Physics, University of Michigan, Ann Arbor, Michigan, United States, 3 Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan, United States, 5 Chemical Engineering, Yale University , New Haven, Connecticut, United States, 4 Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States
Monday, 12/1Transfer Poster G5.24 to G2.5 @ 11:45 AMThree Dimensional Patterning of Indium Tin Oxide and Its Application to Hemispherical Organic Focal Plane Arrays. Xin Xu
G3: Large-Area Compatible Processes and Materials I
Monday PM, December 01, 2008
Room 207 (Hynes)
2:30 PM - **G3.1
ZnO Thin-film Transistors Deposited by a High-speed Continuous Atomic Layer Process.
Shelby Nelson 1 , Mitchell Burberry 1 , Diane Freeman 1 , Peter Cowdery-Corvan 1 , Lee Tutt 1 , David Levy 1 Show Abstract
1 , Eastman Kodak Company, Rochester, New York, United States
3:00 PM - G3.2
Rheology of Thin Polymeric Coatings: In Situ Assessment of Rheology for Process Design.
Amélie Revaux 1 , Jérémie Teisseire 1 , Etienne Barthel 1 , Maud Foresti 2 , Ingve Simonsen 3 , Elin Sondergard 1 Show Abstract
1 Surface du Verre et Interfaces, CNRS/Saint-Gobain, Aubervilliers France, 2 O2M, Saint-Gobain Recherche, Aubervilliers France, 3 Physics Department, NTNU, Trondheim Norway
Rheology is a key issue for processing thin films of advanced functional polymeric materials. In particular complex devices require the 3D structuration of the film for which hot embossing is a very efficient process. Here we address the problem of the rheology of thin polymeric films in two different ways. For polymer embossing, the viscous flow is a key issue: embossing large scale structures on thin films result in confined viscous flow. Assuming newtonian behavior, we propose an analytical solution for the viscous flow of fluid films with periodic boundary conditions. The solution quantifies the impact of confinement on the structuration dynamics and is a guideline for process design. From this general model, the relevant limits are recovered: bulk relaxation for thick films and lubrication approximation for very thin films. Conversely, in numerous cases, it is necessary to assess the film rheology directly because bulk samples are either not available or not relevant. In such cases, the relaxation of structures under the action of surface tension is an interesting technique for rheology characterization. For that purpose, we have developped an in situ multiple order diffraction technique which allows direct monitoring of the height and shape of the structures. We demonstrate the use of the method through quantification of the impact of confinement on surface relaxation of PMMA structures.
3:15 PM - G3.3
Single and Multi-domain Thin Films of Pentacene Formed by Transferring Crystals Dispersed in Liquid Media.
Takashi Minakata 1 Show Abstract
1 Central R&D Laboratories, Asahi-KASEI Corporation, Fuji-shi, Shizuoka-ken, Japan
3:30 PM - **G3.4
Stability and Mechanical Properties of Organic Thin-film Transistors Manufactured by Sub-femtoliter Inkjets.
Takao Someya 1 , Tsuyoshi Sekitani 1 , Yoshiaki Noguchi 1 , Tomoyuki Yokota 1 , Ute Zschieschang 2 , Hagen Klauk 2 Show Abstract
1 Quantum-Phase Electronics Center, University of Tokyo, Tokyo Japan, 2 , Max Planck Institute for Solid State Research, Stuttgart Germany
4:00 PM - G3: Processes
G4: Materials and Systems for Emissive Large-Area Displays
Monday PM, December 01, 2008
Room 207 (Hynes)
4:30 PM - **G4.1
OLED Degradation Analysis by Synchrotron Radiation FT-IR Microscopy.
Brian D'Andrade 1 , Patrizia Melpignano 2 , Lisa Vaccari 3 , Giovanni Birarda 3 , Maya Kiskinova 3 , Viviana Biondo 2 Show Abstract
1 , Universal Display Corporation, Ewing, New Jersey, United States, 2 , Centro Ricerche Plast-Optica, Amaro Italy, 3 , Sincrotrone Trieste S.C.p.A., Basovizza Italy
5:00 PM - G4.2
Long-life Red Phosphorescent Organic Light-emitting Devices Having Graded Compositions.
Junji Kido 1 , Myoung-Gu Lee 1 , Yong-Jin Pu 1 , Ken-Ichi Nakayama 1 , Masaaki Yokoyama 1 Show Abstract
1 Organic Device Engineering, Yamagata University, Yonezawa, Yamagata, Japan
Organic light-emitting devices having graded junctions were developed. In such devices, graded junctions between hole-transporting materials (HTM) and electron-transporting materials (ETM) are formed. A typical device structure employed in this study was ITO/ HTM / HTM:ETM (graded composition) / ETM / Al. The organic layers were fabricated by the in-line vacuum evaporator, which was developed in our laboratory. For a red phosphorescent OLED, NP, Ir(piq)3 and BAlq were used as HTM, emitter and ETM respectively. In the device structure of ITO/ NPD / Ir(piq)3 / BAlq / Liq / Al, various patterns of gradual mixing of the organic layers were evaluated. Red emission peaking at 620nm and a high external quantum efficiency of 10 percent were observed. The graded mixing of the NPD/BAlq interface provided the longer lifetime. A lifetime of over 20000 hrs was observed at the initial luminance of 6500 cd/m2, which is equivalent to 200000 hrs at 1000 cd/m2. The long lifetime is attributed to the elimination of interfaces between the materials and degradation of the materials at the interfaces is suppressed.
5:15 PM - G4.3
Tailored Ambipolar Charge-Transporting Host Materials for Blue Electrophosphorescent OLEDs.
Asanga Padmaperuma 1 , Linda Sapochak 1 Show Abstract
1 , Pacific Northwest National Laboratory, Richland, Washington, United States
State-of-the-art OLEDs utilize an organic host material tailored for charge transport physically doped (5-20% by wt) with an organometallic phosphor optimized for light emission efficiency and color. Development of blue phosphorescent OLEDs, a crucial component of organic solid state lighting, is challenging because the host, as well as the charge injection layers require wide band gap materials with triplet exciton energies, ET >2.8 eV. We previously showed that organic phosphine oxide (PO) host materials exhibit good electron injection and transport properties while maintaining ET ~ 3.0 eV. Such materials, however, show no measurable ability to inject and transport holes, making it impossible to achieve charge balance in the recombination zone. Here, we present design strategies for engineering ambipolar charge-transporting PO host materials for blue OLEDs by combining hole-transporting moieties (HTm) with PO-based electron-transporting moieties (ETm). Three design approaches were considered, including: a –HTm and ETm share a common linkage; b –HTm and ETm are spatially separated by an inert spacer; and c –diphosphine oxide ETm is electronically isolated from HTm via P=O moieties. Theoretical modeling using the NWChem computional package was applied to the PO-ETm, a triarylamine-HTm and a combination of the two moieties using the different design approaches to form ambipolar materials. Three energy parameters were considered: HOMO and LUMO energies, intramolecular reorganizational energies (λi), and charge transfer integrals. We find that for each ambipolar charge transporting material design approach the HOMO energy varies slightly, but the LUMO energy is tunable over 1 eV. Computed λi‘s and charge transfer integrals show a stronger dependence upon design approach. These results will be presented and a general strategy for designing ambipolar charge transporting host materials using PO-moieties for blue phosphorescent OLEDs will be discussed.
5:30 PM - G4.4
Solution Processable Triplet Emitters and High Band Gap Hosts Based on Cyclic Phosphazene Cores.
Mui Siang Soh 1 , Alan Sellinger 1 , Alejandra Soriano 2 , Henk Bolink 2 Show Abstract
1 , Institute of Materials Research and Engineering (IMRE) and the Agency for Science, Technology and Research (A*STAR), Republic of Singapore Singapore, 2 , Instituto de Ciencia Molecular (ICMol), Universidad de Valencia, P.O. Box 22085, 46071 Valencia Spain
Triplet based organic light emitting diodes (OLEDs), which offer the potential of using both the singlet and triplet excitons, have gained tremendous attention in recent years for use in full color displays, solid-state lighting and display backlights. In the area of solution processable materials development, there is a particular need for both new emitters and hosts. In this regard, new solution processable host materials with higher triplet energy states, particularly for blue and green emitters, remains a challenge. In this presentation, we report on dendrimers based on 3-dimensional cyclic phosphazene (CP) cores that represent a new class of versatile materials for application in solution processable OLEDs. For example, the dendrimers are easily prepared in high yield from readily available materials using Buchwald-Hartwig amination and Suzuki chemistry to decorate the periphery of the inorganic CP cores with dendrons having emissive and/or host-transport properties. The synthesized dendrimers are completely amorphous with high glass transition temperatures due to their three dimensional architecture. As the dendrimers are monodisperse, they can be purified to a high degree using chromatographic techniques, are soluble in common solvents, and form defect free thin films upon spin and/or dip coating. Furthermore, the dendrons can be selected from triplet and/or high band gap carbazole based moieties to produce highly efficient devices with blue through red emission. The synthesis, characterization, and preliminary device results using these dendrimers as active materials in solution processed OLEDs will be discussed.
Bolink, H.J., Barea, E., Costa, R.D., Santamaria, S.G., Sudhakar, S., Zhen, C., Sellinger, A., “Efficient Blue Emitting Organic Light Emitting Diodes based on Fluorescent Solution Processable Cyclic Phosphazenes”, Org. Elect., 2008, 9(2), 155-163.
Bolink, H.J., Santamaria, S.G., Sudhakar, S., Zhen, C., Sellinger, A., “Solution Processable Phosphorescent Dendrimers based on Cyclic Phosphazenes for use in Organic Light Emitting Diodes (OLEDs)”, Chem. Comm., 2008, 618-620.
Sundarraj, S. Sellinger A., “Nanocomposite Dendrimers based on Cyclic Phosphazene Cores: Amorphous Materials for Electroluminescent Devices”, Macromol. Rap. Comm, 2006, 27(4), 247-254. (journal cover image).
5:45 PM - G4.5
Electrical Properties of a Novel Encapsulation Material for Organic Light-emitting Diodes.
Lin Han 1 , Prashant Mandlik 1 , Sigurd Wagner 1 , Jeff Silvernail 2 , Rui-Qing Ma 2 , Mike Hack 2 , Julie Brown 2 Show Abstract
1 Electrical Engineering, Princeton University, Princeton, New Jersey, United States, 2 , Universal Display Corp., Ewing, New Jersey, United States
We report electrical properties of a novel, highly effective, single-compound encapsulation layer for the protection of organic light emitting displays from oxygen and humidity. OLEDs coated with this material still function after 10,000 hours of accelerated shelf lift test by storage at 65oC and 85% relative humidity. The material is a single-phase hybrid of silica and silicone. It combines the hermeticity of silica glass with the flexibility of silicone rubber in varying ratios. We first describe the deposition of this hybrid material by plasma-enhanced chemical vapor deposition from environmentally friendly precursor gases — oxygen and hexamethyl disiloxane (HMDSO). Then we discuss its electrical properties in the context of a number of chemical and mechanical properties, including infrared absorption spectra, surface roughness and wetting angle, and indentation hardness. We evaluate the electrical properties from capacitance-voltage (at 1 MHz) and current–voltage measurements on p-type Si / hybrid layer / Cr structures. The relative dielectric constant varies from about 4.5 for films whose chemo-mechanical properties are silica-like to 2 for films that essentially are plasma-polymerized silicone. Because films with silica-like properties are promising candidates for other areas outside of OLED encapsulation, such as interlevel dielectrics in flexible electronics, we have studied this novel film for these applications and will report experimental results.
G5: Poster Session: Hybrid and Organic Materials for Large-Area Functional Systems I
Tuesday AM, December 02, 2008
Exhibition Hall D (Hynes)
9:00 PM - G5.1
High-Throughput Solution Processing of Large Scale Graphene.
Vincent Tung 1 2 , Mattew Allen 3 2 , Yang Yang 1 2 , Richard Kaner 3 2 Show Abstract
1 Materials and Science, Uniersity of California, Los Angeles, Los Angeles, California, United States, 2 , California Nano System Institute, Los Angeles, California, United States, 3 Chemistry Department, Uniersity of California, Los Angeles, Los Angeles, California, United States
Single layer graphene is of great interest for electronic applications as an atomically thin, zero band gap semiconductor. Experimental results have been sparse due to the difficulty of creating single layer samples. Here we report a new solution process for the large-scale production of single layered graphene over the entire area of a wafer. By dispersing graphite oxide paper in pure hydrazine we are able to remove oxygen functionalities and restore the planar geometry of single sheets. The graphene sheets produced have the largest area (up to 40 μm x 60 μm) of any yet reported, making them far easier to process. Field effect devices are fabricated by conventional photolithography, displaying currents that are 3 orders of magnitude higher than any previously reported for chemically produced graphene7. The size of these sheets enables a wide range of characterization techniques, including optical microscopy, SEM and AFM performed on the same specimen. This versatile solution process holds great promise for nanoelectronic applications.
9:00 PM - G5.10
Design of Hierarchically Structured Porous Carbons.
Nicolas Brun 1 2 , Gilles Pecastaings 3 , Odile Babot 2 , Marc Birot 2 , Alain Soum 3 , Clément Sanchez 4 , Mathieu Morcrette 5 , Rénal Backov 1 Show Abstract
1 , Centre de Recherche Paul Pascal UPR 8641 CNRS, PESSAC France, 2 , Institut des Sciences Moléculaires UMR 5255 CNRS Université Bordeaux 1, TALENCE France, 3 , Laboratoire de Chimie des Polymères Organiques UMR 5629 CNRS ENSCPB Université Bordeaux 1, PESSAC France, 4 , Laboratoire de Chimie de la Matière Condensée de Paris UMR 7574 CNRS Université Pierre et Marie Curie, PARIS France, 5 , Laboratoire de Réactivité et Chimie des Solides UMR 6007 CNRS Université de Picardie Jules Verne, AMIENS France
9:00 PM - G5.12
Development of New ``High-Speed Deposition" Process for Low-Cost and Flexible Organic Electronic Sensors.
Satoshi Horie 1 , Kenji Ishida 2 , Kei Noda 1 , Shuichiro Kuwajima 1 , Hirofumi Yamada 1 , Kazumi Matsushige 1 Show Abstract
1 , Kyoto university, Kyoto Japan, 2 , Kobe university, Kobe Japan
9:00 PM - G5.13
Easy Functionalisation of High Surface Area Carbon Materials Using Diels-Alder Reactions for Sustainable Catalysis.
Philippe Makowski 1 , Frédéric Goettmann 2 , Arne Thomas 1 , Markus Antonietti 1 Show Abstract
1 , max planck institute of colloids and interfaces, Potsdam Germany, 2 , Institut de chimie separative de Marcoule ICSM, bagnols/Cez France
9:00 PM - G5.14
Tuning Energetic Levels in Nanocrystal Quantum Dots Through Surface Manipulations.
Nir Tessler 1 , Vladislav Medvedev 1 , Michal Soreni-Harari 1 , Nir Yaacobi-Gross 1 Show Abstract
1 Electrical Engineering, Technion. Israel Institute of Technology, Haifa Israel
Tuning of the relative position of energy levels between nanocrystals (guest) and conjugated polymers (host) as well as of inter-nanocrystal (NC) coupling is reported along with the implication on device performance. In the context of LEDs and Photocells, one of the important factors in hybrid polymer-NC devices is the relative position of the energy levels of the components. In LEDs, the conduction and valence bands of the NC should be enclosed within the polymer bands (type I). Conversely, a staggered band alignment is required in a photocell (type II). Band alignments are not easily tunable as they are determined mostly by the material properties. In the context of transistors it is important to enhance the inter-dot coupling (i.e. electronic transport) while keeping the solution processibility.We report on tuning of the electronic level positions with respect to the vacuum level in colloidal InAs NCs using surface ligand exchange. We show that through a choice of ligand the inter-dot coupling is enhanced, thus supporting higher currents. By performing detailed electrochemical as well as scanning tunneling spectroscopy measurements on particles capped with different ligands we show that the organic surface capping layer of the inorganic NC is taking part and affecting its electronic system. The energy levels' shifting is largely dependent on the surface linking group while the polarity of the ligand molecules has a lesser effect. Improved device performance upon energy level tuning and enhanced inter dot coupling are demonstrated in several prototype devices using I-V measurements as well as photocurrent measurements of single and double layer devices.
9:00 PM - G5.15
Functional Monolayer Nanoparticle/polymer Composites Formed by Evaporation Induced Self-assembly at a Fluid Interface.
Shisheng Xiong 1 , Yongqian Gao 2 , Jiebin Pang 1 , John Grey 2 , Jeffrey Brinker 1 3 Show Abstract
1 Department of Chemical Engineering, University of New Mexico, Albuquerque, New Mexico, United States, 2 Department of Chemistry, University of New Mexico, Albuquerque, New Mexico, United States, 3 Advanced Material Laboratory, Sandia National Laboratories, Albuquerque, New Mexico, United States
Nanoparticle (NP)/polymer composite materials exhibiting novel mechanical, electronic and optical properties are under extensive investigation for photovoltaics, light-emitting diodes and sensors. However, polydispersity of NP size and severe aggregation of NPs within the polymer matrix, are remain obstacles for further applications where a uniform positioning of nanoparticles is generally required. Recently, we have developed a universal, fast and facile method to prepare robust and transferable NP/polymer composites by evaporation-induced self-assembly at a fluid interface (JACS 2008). The nanoparticles embedded within the polymer matrix are 2D monolayer arrays, ordered in a hexagonal close-packed (hcp) arrangement. Ultra-thin, ordred films exceeding several cm2 can be assembled in seconds and transferred to arbitrary substrates. This approach represents a new means to attain very highly loaded yet flexible particle/polymer nanocomposites, which have eluded most synthetic efforts to date. Moreover, this kind of nanocomposite is tunable by either changing the nanoparticulate building blocks, or using different functional polymers. For instance, with PMMA serving as a negative photoresist, we have successfully demonstrated two modes of electron beam lithographic patterning essential for device fabrication and have shown sub 100-nm features with sub-nm edge roughness. Additionally, metallic and semiconductor nanoparticles have been assembled within a conjugated polymer and transferred onto electrode arrays for investigation of charge transport through NP/polymer film using combined spectroscopic imaging and I-V techniques.
9:00 PM - G5.16
Changes in Conductance of Pentacene at Electronic Interfaces.
Soonjoo Seo 1 , Guowen Peng 2 , Manos Mavrikakis 2 , Robert Hamers 3 , Paul Evans 4 Show Abstract
1 Materials Science, University of Wisconsin-Madison, Madison, Wisconsin, United States, 2 Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, Wisconsin, United States, 3 Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States, 4 Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin, United States
We have used scanning tunneling microscopy (STM) to probe the formation and electronic properties of a nitrobenzene self-assembled monolayer between Si (001) and a pentacene thin film. Differential conductance measurements were performed on few molecular-layer thick pentacene thin films on nitrobenzene-passivated, styrene-passivated and unpassivated Si (001) surfaces using scanning tunneling spectroscopy (STS). High-resolution STM images in conjunction with state-of-the-art density functional theory (DFT) total energy calculations and STM simulations show that nitrobenzene forms a well-ordered monolayer on Si (001). The conductance of pentacene on nitrobenzene-passivated Si (001) is different from that of pentacene on styrene-passivated and bare Si surfaces. The apparent energy gap in tunneling spectra was larger for pentacene on nitrobenzene than for the other surfaces by a factor of two. Our results can provide insight into the energy band lineups of an organic semiconductor at an electronic interface which are related to the charge transport characteristics of organic semiconductors.
9:00 PM - G5.17
Inkjet-Printed Libraries of PPE-PPV Copolymers with Tunable Optical Properties.
Daniel A. M. Egbe 1 2 , Emine Tekin 2 , Thomas Blaudeck 1 , Ulrich Schubert 2 3 , Reinhard Baumann 1 Show Abstract
1 Print and Media Technology, TU Chemnitz, Chemnitz Germany, 2 Macromolecular Chemistry and Nanoscience, TU Eindhoven, Eindhoven Netherlands, 3 Organic and Macromolecular Chemistry, FSU Jena, Jena Germany
Patterning functional materials by inkjet printing has become an established technology for a variety of applications envisaged in organic and large-area electronics such as organic photovoltaic devices or light-emitting diodes. For any of those, tunability of the properties of the film of conjugated polymers is important. In particular, alkoxy side chains attached to the backbone may grant not only an appropriate processability by enhancing the solubility of the polymers, they also can affect the optical and electronic properties of the film. In this contribution, we report on the synergetic effects of position and length of side chains, film thickness and thermal treatment on the optical properties of a series of defect-free, four-fold alkoxy-substituted poly(p-phenylene-ethynylene)-alt-poly(p-phenylene-vinylene)s (PPE-PPV). These polymers were synthesized via a Horner-Wadsworth-Emmons olefination reaction of luminophoric dialdehydes and bisphosphonate esters The thickness libraries of the different PPE-PPVs were prepared by controlled inkjet printing, with the optical properties of the printed libraries screened by high-throughput methods. It was found that the emission colors of the investigated polymers strongly depend on the interchain interactions which increase with increasing film thickness and influenced by the side chains. In conclusion, we could establish a correlation between the intensity of the S1-0 → S0-2 vibronic transition and the red shift of the emission color. Upon annealing at 70 °C for 2h, white emission was observed from thick printed films. This finding is tentatively ascribed to broadened emission spectra covering the whole visible region of the light spectrum and may be attributed to an increased aggregation due to an enhanced planarization of the polymer backbone. Further, the results for inkjet printing of related nanocomposite materials are discussed.
9:00 PM - G5.19
Isolation of Aging Components in Copper Phthalocyanine Organic Transistors.
James Royer 1 , J. Park 2 , C. Colesniuc 3 , A. Sharoni 3 , F. Bohrer 1 , I. Schuller 3 , W. Trogler 1 , A. Kummel 1 Show Abstract
1 Chemistry and Biochemistry, University of California San Diego, La Jolla, California, United States, 2 Materials Science and Engineering Program, University of California San Diego, La Jolla, California, United States, 3 Physics, University of California San Diego, La Jolla, California, United States
A systematic approach to isolating the cause of device degradation (“aging”) in copper phthalocyanine (CuPc) organic thin film transistors (OTFTs) is presented. Aging is one of the primary impediments to the widespread deployment of OTFTs in gas sensors and as drivers for OLEDs. OTFTs with thick (~1000ML) CuPc layers were employed to study aging and the reversal of aging since the effects are most dramatic in thick organic layer OTFTs. Exposure of thick CuPc OTFTs to a sequence of environments including ambient air, clean dry air (20% O2/N2), water vapor and N2 gas isolated the causes of device aging in thick CuPc OTFTs. Initial exposure to ambient air increases the conductivity of the CuPc film but also causes rapid device aging characterized by an increased threshold voltage and the loss of saturation behavior. This is consistent with a loss of control of the channel conductivity by modulation of the gate bias. Conversely, exposure of thick CuPc OTFTs to clean dry air, H2O/N2 mixtures, or clean air/H2O mixtures does not result in aging, consistent with O2, H2O and O2/H2O products not being responsible for the aging. Furthermore, recovery of the threshold voltage and saturation behavior in fully aged thick CuPc devices requires displacement of the agents responsible for aging by H2O at the CuPc grain boundaries. The data is consistent with trace strong oxidants in ambient air being responsible for OTFT aging via formation of fixed charge. The aging effect is only present in thick films and is attributed to dissociative chemisorbing of strong oxidants (e.g. NOx and O3) in grain boundaries to form fixed charges which degrade the control of the OTFT channel conductivity by the gate bias.
9:00 PM - G5.2
Bistable Electrical Switching and Rewritable Memory Effect in a Thin Film Acrylate Copolymer Containing Carbazole-Oxadiazole Donor-Acceptor Pendant Groups.
Eric Teo 1 , Qidan Ling 2 , Siew Lay Lim 2 , En Tang Kang 2 , Daniel Siu Hung Chan 1 , Chun Xiang Zhu 1 Show Abstract
1 Electrical and Computer Engineering, National University of Singapore, Singapore Singapore, 2 Chemical and Biomolecular Engineering, National University of Singapore, Singapore Singapore
The advantage of using organic or polymer materials for memory application lies in the fact that their electronic properties can be easily tuned, by structural design, synthesis and modification, to exhibit a series of memory functions. We have previously reported that an acrylate polymer with hole-transporting carbazole pendant groups can function effectively as a non-volatile WORM memory device. The WORM memory effect was attributed to the presence of a spacer unit between the pendant carbazole group and the polymer backbone. The spacer unit allowed the transition of the pendant carbazole groups from a disoriented state (OFF state) to an ordered face-to-face (or regioregular) conformation (ON state) at the threshold voltage. In this work, we report a change in memory function and mechanism when oxadiazole (acceptor) pendant groups are incorporated into the main chain. The flash (rewritable) memory behavior of the newly synthesized acrylate copolymer material, poly(2-(9H-carbazol-9-yl)ethyl methacrylate-co-4-(5-(4-tert-butylphenyl-1,3,4-oxadiazol-2-yl)phenyl methacrylate), or PCzOx, containing the carbazole-oxadiazole donor-acceptor pendant groups, has been demonstrated. The basic device structure is a MIM structure with Indium-Tin-Oxide (ITO)/glass as the substrate, our synthesized polymer material PCzOx as the active layer and Al as the top electrode. The toluene solution of PCzOx was spin-coated on the ITO, followed by solvent removal in a vacuum chamber. Finally, Al was thermally evaporated through shadow mask onto the PCzOx film. The memory effect of PCzOx was observed in the I-V characteristic of the MIM structure. The as-fabricated device is found to be in its OFF state, showing a current density of ~10-3 Acm-2, and can be programmed to ON state of current density ~10 Acm-2 at a threshold voltage of -1.8 V in the negative sweep. The ON state can be erased to the OFF state by using a reverse sweep (in this case positive sweep) and upon reaching a bias of +3.6 V. Subsequent switching between the ON state and the OFF state (the programming and erasing cycle) can be repeated with good accuracy for the write and erase voltage. The rewritable memory device exhibited a high ON/OFF current ratio of 103, was stable in both OFF and ON states after 107 read cycles, and showed that both the retention time in the ON and OFF state could be sustained under a 2 h voltage stress test. The J-V curve in the OFF state can be well fitted with the Schottky emission model, whereas that of the ON state can be fitted with the Ohmic model. The proposed mechanism based on charge transfer process is supported by the density function theory (DFT) simulation, as well as the UV-visible absorption spectroscopy. The solution-processable copolymer thin film is potentially useful for application in large-area flash memory devices.
9:00 PM - G5.20
Excited State Dynamics in Zn Phthalocyanines.
Leonardo De Boni 1 , Erick Piovesan 1 , Luciana Gaffo 2 , Cleber Mendonca 1 Show Abstract
1 IFSC, University of Sao Paulo, Sao Carlos, Sao Paulo, Brazil, 2 Departamento de Química, Univ. Estadual de Maringa, Maringa Brazil
Phthalocyanines are macrocyclic organic compounds which present excellent stability, and whose optical and electrical properties can be tuned by varying the peripheral groups, the central metal ion as well as the way molecules are assembled. Such features make phthalocyanines promising candidates for a broad range of applications, from organic solar cells to photo-dynamic therapy of cancer. Thanks to the intense reverse saturable absorption exhibited by phthalocyanines, they have been used in several optical applications. Reverse saturable absorption occurs when the excited state absorption cross-section exceeds that of the ground state. In general, for macrocyclic compounds reverse saturable absorption follows from an intersystem crossing from a higher excited singlet state to an excited triplet state. Consequently, the reverse saturable absorption efficiency depends upon the properties of excited states, such as excited states lifetimes, intersystem crossing time and cross-sections.In this work, we investigate the nonlinear absorption dynamics of Zn phthalocyanine in dimethyl sulfoxide. We used single pulse and pulse train Z-scan techniques to determine the dynamics and absorption cross-sections of singlet and triplet states at 532 nm. The excited singlet state absorption cross-section was determined to be 3.2 times higher than the ground state one, giving rise to reverse saturable absorption. We also observed that reverse saturable absorption occurs from the triplet state, after its population by intersystem crossing, whose characteristic time was determined to be 8.9 ns. The triplet state absorption cross-section determined is 2.6 times higher than the ground state one. In addition, we used the white light continuum Z-scan to evaluate the singlet excited state spectrum from 450 nm to 710 nm. The results show two well defined regions, one, above 600 nm, where reverse saturable absorption is predominant. Below 600 nm, we detected a strong saturable absorption. A three-energy-level diagram was used to explain the experimental results, leading to the excited state absorption cross-section determination from 450 nm up to 710 nm. The high excited singlet and triplet states absorption cross-sections of phthalocyanines indicates its use in application requiring reverse saturated absorption in a broad spectral band
9:00 PM - G5.21
Layer-by-Layer Assemblies of Polyelectrolytes with Inorganic Nanoparticles and Organic Functional Molecules.
Sang-Mi Jeon 1 2 , Ki-Se Kim 1 2 , Byeong-Hyeok Sohn 1 2 Show Abstract
1 Chemistry, NANO System Institute, Seoul National University, Seoul Korea (the Republic of), 2 , Center for Nanostructured Materials and Technology, Seoul Korea (the Republic of)
The layer-by-layer (LbL) assembling method based on electrostatic interaction between oppositely charged materials has been employed to create multilayered thin films with a well-controlled thickness in a nanometer scale. In addition, a variety of functional materials such as conducting polymers, organic dyes, metal and semiconductor nanoparticles have been incorporated into LbL thin films. Moreover, the LbL method can effectively generate multifunctional thin films by incorporating more than a single functional component into thin films. In this study, we demonstrate the fabrication of LbL assemblies of polyelectrolytes with inorganic semiconductor nanoparticles and organic fluorescent dyes. We synthesized semiconductor ZnO nanoparticles, of which surface were modified with silane compounds for stable LbL deposition. Fluorophore-labeled polyelectrolytes were also synthesized to attach dye molecules to polyelectrolytes. Then, thin films were fabricated with surface-modified ZnO nanoparticles, pure polyelectrolytes, and dye-labeled polyelectrolytes by the LbL method. Nanoparticles and fluorophores were independently inserted into the desired layer. To control the fluorescence resonance energy transfer (FRET) in the films, the mutual distances between fluorophores and semiconductor nanoparticles were controlled by the number of layers of pure polyelectrolyte layers. Since a variety of functional nanoparticles and molecules can be incorporated into LbL assemblies, hybrid LbL assemblies can be used in many applications such as solar cells and sensors which require the precise control over the distances among functional ingredients.
9:00 PM - G5.23
Layer-by-Layer Polyelectrolyte Multilayer Stabilized by Epoxy Reaction on Polymer Substrates.
Heekyung Lee 1 , Eunju Lee 1 , Hongdoo Kim 1 Show Abstract
1 Chemistry, Kyung Hee University, Yongin, Kyungkido, Korea (the Republic of)
Among various techniques to fabricate ultrathin film coating on the polymer substrate, the method to assemble layer-by-layer (LbL) polyelectrolyte multilayer(PEM) is one of the choices, which gives the capability of large area fabrication and the environmentally benign processing condition using water as solvent. Although this method using pH-adjusted PAH and PAA as polyelectrolyte dipping solutions is simple and easy, it has some draw-backs such that the film is unstable in chemical environments and mechanical property is poor. Fabricated ultrathin film does not keep stable conditions because the self-assembled PEM can be easily removed using acidic or basic solution. In order to overcome this, we have studied the epoxy reaction with PAH and PAA. Epoxy group may react and crosslink with amine or carboxylic group in PEM. GPTMS((3-glycidyloxypropyl)trimethoxysilane) having epoxy group was used as one of coating solution to crosslink with PEM. The trimethoxysilane group helps increase hardness of coating by reaction with colloidal silica suspension in the next process. Another coating solution was prepared by adding trimethoxysilane group solution to colloidal silica suspension through sol-gel method to strengthen the surface hardness of this film. Organic-inorganic hybrid coating using sol-gel method improved the chemical stability and the mechanical hardness on plastic substrates. The chemical and mechanical characteristics of PEM were investigated along with methoxysilane content in the solution. In order to demonstrate the epoxy reaction in LbL multilayer, the reaction was monitored by FT-IR spectra. The epoxy vibrational peak on FT-IR spectrum was disappeared as the reaction was proceeded. With GPTMS and nano silica suspension, the surface hardness was greatly improved. Also, it was found that crosslinking of amine-epoxy group can be done by either heating or UV exposure. The curing method using UV exposure has some advantages such as reduction in reaction time and generating patterns onto the specified area. Since the unexposed area of PEM may be easily removed using acidic solution, it is possible to generate sophisticated pattern on the plastic plate. As an example of this method, copper wiring pattern was made on polymer substrates through electroless plating and the adhesion between Cu and polymer substrate was improved.
9:00 PM - G5.25
Nanoparticle-assisted High Photoconductive Gain in Polymer/fullerene Matrix.
Hsiang-Yu Chen 1 , Michael Lo 2 , Guanwen Yang 1 , Harold Monbouquette 2 , Yang Yang 1 Show Abstract
1 Materials Science and Eng., UCLA, Los Angeles, California, United States, 2 Chemical and Biomolecular Engineering, UCLA, LA, California, United States
Polymer/inorganic nanocrystal composites offer an attractive means to combine the merits of organic and inorganic materials into novel electronic and photonic systems. However, many applications of these composites are limited by 1) the solubility of the nanocrystals in the same solvent as that used for polymers, 2) the lower charge transfer rate between polymer and nanocrystal, and 3) the inefficient electron hopping rate between neighboring nanocrystals. To prevent nanocrystals from aggregating in the solvent, surface ligands such as oleic acid (OA) or tri-n-octylphosphine oxide (TOPO) are often used to enable dispersion of the nanoparticles or nanorods in the solvent; but these ligands hinder charge transfer from polymer to nanocrystals and carrier transport between nanocrystals. Much work has been done to modify the ligands to enhance the charge transfer rate as well as the solubility of the nanocrystals in polymer solutions. In our work, a high photoconductive gain has been achieved by blending cadmium telluride (CdTe) nanoparticles (NPs) into a polymer/fullerene matrix followed by a solvent annealing process. The NP surface capping ligand, N-phenyl-N’-methyldithiocarbamate, renders the NPs highly soluble in the polymer blend thereby enabling high nanocrystal loadings. An external quantum efficiency (EQE) as high as ~8000% (at 350nm) is reached at -4.5V. To our knowledge, this is the highest photoconductive gain obtained so far in polymer-based system under such low applied voltages. Hole-dominant devices coupled with AFM images are studied to uncover the probable mechanism. We observe a higher concentration of CdTe NPs is located near the cathode/polymer interface. These NPs with trapped electrons assist hole injection into the polymer under reverse bias, which contributes to greater than 100% EQE.
9:00 PM - G5.26
Selective Mercury Ion-Sensing with Phosphorescent Ir(III) Complexes.
Dong Ryeol Whang 1 , Youngmin You 1 , Soo Young Park 1 Show Abstract
1 Department of Materials Science and Engineering, Seoul National Univeristy, Seoul Korea (the Republic of)
We report on a selective sensing of Hg2+ with phosphorescent cyclometalated heteroleptic Ir(III) complexes consisting of phenylpyridine-based cyclometalating ligands and an β-diketonate ancillary ligand. The complexes showed very selective responses only to Hg2+ among many different metal ions. Multi-signaling and naked-eye detection of Hg2+ were achieved through the changes in both absorption color and phosphorescence intensity by forming 1:1 complex. Binding constant for the mercury ion was found to be 1.18 × 104 M-1, and the response was observable immediately. From a series of sensing experiments for reference compounds and NMR study, we could elucidate that the α-carbon of the β-diketonate ancillary ligand was a binding site for Hg2+. The phosphorescence quenching mechanism upon Hg2+ binding was explored by quantum chemical calculations.
9:00 PM - G5.28
Low Dielectric Constant Materials Based on Thermally Curable Cyclotriphosphazene Compounds.
Ho Lim 1 , Ji young Chang 1 Show Abstract
1 , Seoul National university, Seoul Korea (the Republic of)
The demand for the low dielectric constant and low dielectric loss materials has increased significantly in recent years as the electronic devices are getting faster and smaller. In this work, we prepared thermoset polymers based on cyclotriphosphazenes, which showed excellent dielectric properties. They also exhibited unusual thermal properties such as flame retardancy and self-extinguishibility due to skeletal nitrogen and phosphorus atoms of a cyclotriphosphazene ring. We synthesized soluble and curable cyclotriphosphazenes by substitution reaction of hexachlorocyclotriphosphazene with thermally reactive groups. The compounds were polymerized thermally to yield highly cross-linked materials. We chose styrene and acetylene compounds as reactive side groups, which are thermally curable under moderate conditions without the evolution of volatiles. Hexakisstyreneoxycyclotriphosphazene (HSP) was prepared by substitution reaction of hexachlorocyclotriphosphazene with sodium salt of 4-hydroxystyrene. The HSP was polymerized in a mold at 180 °C for 2 h under pressure. PolyHSP showed very low dielectric constant (k = 2.4) and low dielectric loss (tanδ = 1 x 10-3). The initial thermal degradation temperature was over 450 °C. No glass transition temperature was observed. We were able to further lower the dielectric constant and dielectric loss by introducing a bulky side group as a cosubstituent. When an acetylene compound was used as a curable group, the resulting polymers showed lower dielectric constant but higher dielectric loss than corresponding polymers obtained from styrene substituted cyclotriphosphazenes.
9:00 PM - G5.29
Bulk-Heterojunction Type Organic Solar Cells Based on New Branched Alkyl Oligothiophenes.
Yuji Yoshida 1 , Kenichi Sasaki 1 2 , Shuichi Nagamatsu 1 3 , Ming Lu 1 4 , Reiko Azumi 1 , Kiyoshi Yase 1 , Masafumi Yamashita 2 Show Abstract
1 , National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Japan, 2 , Tokyo Science University, Noda Japan, 3 , Kyushu Institute of Technology, Iizuka Japan, 4 , Harbin Normal University, Harbin China
Recently, organic thin film solar cells show promise as future low cost solar energy. Especially, it is important to develop the solution-process solar cells because of remarkably decreasing the process cost. Polymer bulk-heterojunction solar cells are so close to the solution that many researchers have developed various soluble semiconducting materials. As well known, the combination of poly(3-hexylthiophene) (P3HT) with soluble fullerene (PCBM) shows highest efficient for bulk-heterojunction solar cells.Oligothiophenes are excellent semiconducting materials for many applications of field effect transistors, solar cells, light-emitting diodes, etc. However, it is difficult to develop high performance and good soluble oligothiophenes. According to the results of previous research, the relationship between carrier mobility and solubility is counterbalanced each other.In this study, we newly synthesized excellent soluble oligothiophene derivertives, 5,5''''-bis(2-hexyldecyl)-2,2':5',2'':5'',2''':5''',2''''-quinquethienyl (BHD5T) and sexithienyl (BHD6T) for solution-process organic devices. As our first trial, we fabricated bulk-heterojunction type solar cells of this oligothiophenes and PCBM.The active layer was spin-coated from the mixed solution of soluble BHD5T/BHD6T and PCBM at the weight ratio of 1:1 in chloroform solution. The device structure is composed of ITO/PEDOT:PSS/Active layer/LiF/Al. The I-V characteristics of the devices were measured under illumination of Xenon lamp at the power of 100mW/cm2. As the results, the power efficiency of this solar cell was up to 0.3 %. It is easily possible to improve the efficiency up to about 1% by tuning device structures such as an exciton-blocking layer, etc.
9:00 PM - G5.3
Partially-Fluorinated Large Acenes for Organic Electronics.
Balaji Purushothaman 1 , Sean Parkin 1 , John Anthony 1 Show Abstract
1 Department of Chemistry, University of Kentucky, Lexington, Kentucky, United States
Electronic devices based on organic materials have been an area of intense research due to their suitability to low cost solution processing techniques such as spin coating and ink-jet printing. Among the small-molecule semiconductors, acene based materials have been the most widely studied class of organic compounds due to their impressive electronic properties such as lower reorganization energy, reduced band gap and higher charge carrier mobility predicted by theoretical studies. However they have poor solubilty, π overlap and are highly unstable. The Anthony group has successfully demonstrated that by peri-functionalization with trialkylsilyl ethynyl groups π – stacking, solubility and stability of acenes can be improved. This approach has not only been applied to pentacenes but also successfully on higher acenes such as hexacene and heptacene. Acene based semiconductors are inherently p-type or hole transporting materials and in recent years efforts have been made towards synthesis of n-type materials by introducing electron withdrawing groups to the acene chromophore. Perfluoropentacene has been reported in the literature and the molecule behaves a n-type material. Introduction fluorine lowers the LUMO energy level of the molecule there by enabling electrons to be injected into the LUMO. Addition of fluorine is also known to improve the environmental stability and π – stacking in molecules by increasing intermolecular interactions between the electronegative fluorine atoms and π electron rich acene chromophore. Recently Anthony group has shown that partialy fluorinated anthradithiophenes exhibit higher mobility and environmental stability without altering the p-type behaviour of these molecules. We have applied same approach to synthesize partially fluorinated acenes of varying degree to improve the photostability and π – stacking in pentacene and hexacene. The effect of partial fluorination on LUMO energies will also be presented.
9:00 PM - G5.30
Large-scale Functional Surface Nanostructures and Their Diverse Applications.
Yong Lei 1 , Gerhard Wilde 1 Show Abstract
1 Institute of Materials Physics, University of Muenster, Muenster Germany
9:00 PM - G5.31
Fabrication of Nanostructures Based on Nanocoating and Lithography Fabrication of Gold Nanofin Arrays Embedded in Polymer Film and its Application for Flexible, Transparent Anisotropic Conductive Film.
Wakana Kubo 1 , Shigenori Fujikawa 1 , Toyoki Kunitake 1 Show Abstract
1 , RIKEN, Saitama Japan
9:00 PM - G5.32
Realisation and Characterisation of Flexible Vertical Channel Organic Field Effect Transistors.
Giorgio Mattana 1 , Piero Cosseddu 1 , Annalisa Bonfiglio 1 Show Abstract
1 , DIEE, Dept. of Electrical and Electronic Engineering, University of Cagliari, Cagliari Italy
Monday 12/1Transfer Oral G2.3 @ 11:15 AM to Poster G5.32Realisation and Characterisation of Flexible Vertical Channel Organic Field Effect Transistors. Giorgio Mattana
9:00 PM - G5.4
Low Temperature Transparent Nanoplatelet Hybrid Gas Barrier Coating Materials via Sol-gel Process.
Masahiro Asuka 1 2 , Wolfgang Sigmund 1 Show Abstract
1 Materials Sciences & Engineering, University of Florida, Gainesville, Florida, United States, 2 High Performance plastics company, Sekisui Chemical Co.LTD., Tokyo Japan
A novel hybrid coating based on a combination of nanoparticles, sol-gel and organic chemistry has been developed. It can be applied to a large variety of surfaces even at low processing temperatures. Low temperatures allow fabrication of the hybrid films on polymers.Nanoplatelets composite hybrid organic/inorganic coating materials have been successfully prepared via this sol-gel process. Transparent coatings from flexible to brittle can be obtained depending on the ratio of the inorganic/organic reagents. Thick films of more than 10 micrometer were achieved via single time dip coating. These barrier coatings are highly transparent (more than 95%) in the visible light while containing more than 60wt% ceramic nanoplatelets. Several substrates have been successfully tested including poly (ethylene terephthalate ) (PET). Moreover these films have excellent gas barrier properties for water vapor and excellent mechanical properties such as flexibility, which are important considerations in opto-electronic devices. Due to the incorporation of organic functional groups for the flexibility of the hybrid film, 3-Glycidoxypropyltrimethoxysilane(GPTMS) was adopted not only as a network former but also as a dispersing agent for nanoparticles during the preparation of the hybrid materials. The talk will present latest results on the characterization of the hybrid barrier coatings. Transmission electron microscopy, nanoindentation and Fourier transform infrared spectroscopy and Fourier transform Raman spectroscopy will be used to explain the development of the structure and its properties. Furthermore, the improvements in barrier coating towards water vapor permeation on PET will be discussed.
9:00 PM - G5.6
Multiscale Chemical Patterning of Self-Assembled Monolayers via Controlled Plasma Flow in Poly(dimethylsiloxane) Microchannels.
Meng-Hsien Lin 1 , Chi-Fan Chen 1 , Hung-Wei Shiu 2 , Chia-Hao Chen 2 , Shangjr (Felix) Gwo 1 3 Show Abstract
1 , Nanoengineering and Microsystems, Hsinchu Taiwan, 2 , National Synchrotron Radiation Research Center, Hsinchu Taiwan, 3 physics, physics, Hsinchu Taiwan
Integration of individual nanoscale objects into functional structures represents a key challenge for emerging fields of nanotechnology. Especially for the interfacing of nanoscopic devices with the macroscopic world, a large number of hierarchical and multilength-scale organization steps based on patterning and controlled assembly are required to implement practical nanodevice applications. Recently, soft lithographic approaches such as microcontact printing, replica molding, and nanoimprint have been developed to overcome this difficulty. The main concerns of soft lithography are durability of stamp, uniformity of large-area processing, and possibility of hierarchical structures. To enhance the applicability of soft lithography, we present here our recent results based on local plasma-induced chemical modification of organosilane monolayers using controlled plasma flow in poly(dimethylsiloxane) (PDMS) stamps.In order to achieve site-specific chemical modification and large-area patterning, we utilized PDMS elastomeric stamps fabricated with microchannel patterns. By directly contacting the PDMS stamps with surfaces terminated by organosilane self-assembled monolayers (SAMs), we can realize the confinement and controlled flow of low-power air plasma within the designated areas of organosilane SAM surfaces. We have successfully applied this method to multiple length scales ranging from full-wafer to sub-micron scale. Furthermore, the patterning resolution can reach a precision of few nanometers, judging by the patterned line edge. Using the plasma-patterned organosilane SAMs, we have demonstrated the possibilities of subsequent templated self-assembly steps for grafting dissimilar SAMs onto designated areas or for site-selective adsorption of functionalized nanoparticles.In this study, we have also understood the nature of plasma-induced chemical modification. First, the technique of synchrotron-radiation X-ray photoelectron spectroscopy (XPS) was applied to confirm the conversion of the original surface methyl groups into three main oxidized groups in the forms of hydroxyl, carbonyl and carboxyl groups. Second, by using focused synchrotron-radiation X-ray scanning photoemission microscopy and spectroscopy (SPEM/S), we have mapped regions of different functional groups on the modified surface, which are in excellent agreement with the PDMS pattern. Finally, by using scanning Kelvin probe microscopy (SKPM), the surface potential changes were quantitatively measured at the surfaces of plasma-modified, dissimilar SAM, and Au-nanoparticles-adsorbed regions. By comparing all the microscopic results [SPEM, SKPM, and scanning electron microscopy (SEM)], we confirm that the plasma-based pattern transfer using PDMS microchannel stamps is very faithful in terms of chemical conversion and spatial size/shape.
9:00 PM - G5.7
Soft Lithographic Approaches for Patterning of Quantum Dot Optoelectronics
Jixin Chen 1 , Yang-Hsiang Chan 1 , Dong Hee Son 1 , James Batteas 1 Show Abstract
1 Department of Chemistry, Texas A&M University, College Station, Texas, United States
Here we demonstrate the direct photolithographic patterning of quantum dot (QD) thin films on surfaces over large areas. CdSe QDs were prepared as thin films of one or multiple particle layers in thickness on solid supports. Photopatterning of these films can be accomplished by local photo-oxidation using scanning confocal laser microscopy as well as by conventional photolithography. Local photo-oxidation of the stabilized film results in significant wavelength shifting of the CdSe quantum dots allowing selective tuning of the local emission wavelength by ca. 50 nm or more affording multiple colors to be spatially patterned from a single starting material. Additionally, the luminescence of the patterned structures can be subsequently turned “off” and “on” by simple ligand exchange. The ability to create nanoscopic structures using scanning laser lithography as well larger arrays via conventional photolithographic methods provide a facile, scalable approach, for creating QD based devices with tunable optical properties.
9:00 PM - G5.8
The Supramolecular Chemistry of Silica-based Organic-Inorganic Hybrid Materials as Chemosensor for Toxic Metal Ions.
Jong Hwa Jung 1 , Doo Ri Bae 1 , Hey Young Lee 1 , Won Seok Han 1 , Eun-jeong Kim 1 , Namjun Cho 2 Show Abstract
1 Chemistry, Gyeongsang National University , Jinju Korea (the Republic of), 2 Applied Chemical Engineering, Korea University of Technology & Education, Chonan Korea (the Republic of)
With recent advances in nanomaterials and nanotechnologies, new methods are emerging to design optical sensors and biosensors, and to develop highly sensitive solid-state sensors. However, in recent years, SBA-15 and MCM-41 have attracted significant interest for the development of optical chemical sensors. Although these materials offer considerable advantages over other methods in the area of sensing technologies, there is still a growing demand to solve one of the major technological challenges in nano-optical sensor: the detection and determination of environmentally important toxic species at a low level of concentration with a rapid-assessment process. Based on this idea, we designed and synthesized an azo-coupled macrocyclic receptor 1, and then grafted 1 onto the surface of SNT as a new approach to the development of nanomaterial chemosensors. The SNT-1 (silica nanotube immobilized with 1) as heterogeneous “naked-eye” colorimetric and spectrophotometric cation sensor was prepared by immobilization of the azo-coupled macrocyclic receptor 1 on the silica nanotube (SNT) via sol-gel reaction. The optical sensing ability of SNT-1 was studied by addition of metal ions such as Ag+, Co2+, Cd2+, Pb2+, Zn2+, Fe3+, Cu2+, and Hg2+ (all as nitrates) in water. Upon the addition of Hg2+ in suspension SNT-1 resulted in a color change from yellow to violet. This is novel rare example for chromogenic sensing of a specific metal ion by inorganic nanotubes. On the other hand, no significant changes in color were observed in the parallel experiments with Co2+, Cd2+, Pb2+, Zn2+, Fe3+, Cu2+, and Ag+. These findings confirm that SNT-1 can be useful as chemosensors for selective detection of Hg2+ over a range of metal ions. More interestingly, SNT-1 by the addition of NO3- and ClO4- was observed color change from yellow to violet and pink, respectively. However, no color changes were observed upon addition of Cl-, Br-, I-, SCN-, or SO42-. Furthermore, the extraction ability of the SNT-1 was also estimated by measuring the amount of Hg2+ adsorbed on the SNT-1 by ion chromatography, resulting in 95% of Hg2+ ion being extracted by SNT-1, suggesting that the SNT-1 is potentially useful as a stationary phase for separation of Hg2+ in liquid chromatography. In order to extend above performance to the portable chemosensor kit, SNT-1 was coated with 50 µm thickness onto glass substrate. The supported SNT-1 only changed from yellow to violet when dipped into Hg2+ solution. On the other hand, no significant change in color was observed in other metal ions solution. The results imply that the supported SNT-1 is applicable as a portable colorimetric sensor for detection of Hg2+ in the environmental field.
9:00 PM - G5.9
Self-assembled Arrays of Mesoporous Silica Cone-like Particles on Different Patterned Surfaces.
Ahmed Khalil 1 2 , Frank Marlow 1 Show Abstract
1 , Max-Planck-Institute für Kohlenforschung, Mülheim an der Ruhr Germany, 2 Nanoparticle Process Technology, Duisburg-Essen University, Duisburg Germany