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Optoelectronic Devices (optoelectronic + device)
Kinds of Optoelectronic Devices Selected AbstractsZnS Branched Architectures as Optoelectronic Devices and Field EmittersADVANCED MATERIALS, Issue 21 2010Zhi-Gang Chen A unique ZnS branched architecture was fabricated by a facile thermal evaporation method. Stable UV emission at 327,nm and superior field emission with a low turn-on field, a high field-enhancement factor, a large current density, and small fluctuation were observed. [source] Mesoscopic Modelling of Polymer-Based Optoelectronic DevicesPLASMA PROCESSES AND POLYMERS, Issue S1 2007Hélder M. C. Barbosa Abstract Substantial progress has been made in fabricating optoelectronic devices using polymers as an active material. In polymer light emitting diodes (PLEDs), a balanced injection of electrons and holes from the electrodes is fundamental to increase their performance. Using a mesoscopic model based on a generalized Monte-Carlo method, we studied the influence of changing zero-field barrier heights at both electrode,polymer interfaces in the performance of a PLED with an active layer of poly(para -phenylenevinylene) (PPV). Our results show that by controlling the electrodes work functions it is possible to tune the region inside the device where charge recombination preferentially takes place. [source] Preface: phys. stat. sol. (c) 1/10PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2004Eun-Kyung Suh The Fifth International Symposium on Blue Laser and Light Emitting Diodes (ISBLLED-2004) was held in Gyeongju, Korea from 15,19 March 2004. Gyeongju, the ancient capital of the thousand-year Silla kingdom (57 B.C. to 935 A.D.) provided additional pleasure to the participants as an exceptional open-air museum with antique treasures scattered all around the city. During the last decade we have witnessed remarkable developments in wide-gap semiconductors and light emitting devices in the spectral range from the visible to deep UV. The purpose of the Symposium was to provide a forum for intensive discussion on the issues and main progress especially in optoelectronic devices, material growth and characterization, and quantum structures of wide bandgap semiconductors. A total of 243 papers including 220 contributed and 23 invited ones were presented and discussed by 487 participants from 17 countries world-wide. Among them, 154 manuscripts were submitted and reviewed by the usual evaluation process of physica status solidi. Some were rejected or withdrawn, and finally 139 papers are published in the special issues of physica status solidi (a), (b), and (c). We gratefully acknowledge the referees for their careful review. The papers are grouped into 7 categories. The subheadings and the number of papers in each are as follows: Optoelectronic devices, 43; Growth and characterization, 45; Nano and quantum structures, 21; Contacts, 8; Zinc oxide, 9; Indium nitride and indium rich InGaN, 6; Others, 7. The special session of the Symposium, "The LED Highlight", designed partially to meet the challenging targets of the technology, i.e., energy savings and clean environment preservation, drew much attention and is edited as a special coloured section in this issue. The next symposium is scheduled for Montpellier, France, in 2006. We wish the organizers of that symposium the best of luck and hope to see all of the ISBLLED-2004 participants again at ISBLLED-2006. ISBLLED-2004 was sponsored by The Research Society for the Wide-gap Semiconductors, Korean Physical Society, Office of Naval Research, Korea Science and Engineering Foundation, Korea Research Foundation, Korea Association for Photonics Industry Development, Asian Office of Aerospace Research and Development, and Korea Photonics Technology Institute. We would like to thank Ms. E. S. Hwang for her devotion to the preparation and the Proceedings of the symposium including the manuscript handling for publication. [source] Investigation of optical band gap in potassium acid phthalate single crystalCRYSTAL RESEARCH AND TECHNOLOGY, Issue 6 2008S. Krishnan Abstract Optical absorption in photonic crystals of potassium acid phthalate has been measured at room temperature, from which the band gap has been determined and the optical band gap was calculated by using absorption spectrum. The analysis of absorption coefficient in the absorption region reveals a direct band gap of 3.70 eV. Further this study includes the theoretical calculations to determine the optical constant of the material and a technique for photonic band gap tuning which is minimally required to develop the optoelectronic device. It was confirmed that potassium acid phthalate crystal has maximum transparency in the entire visible region and hence it exhibits industrial application oriented properties. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] UV Exposition During Typical Lifestyle Behavior in an Urban EnvironmentPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 3 2010Alois W. Schmalwieser In this study the personal exposure to solar UV radiation in an urban environment was measured. Lifestyle in an urban environment is characterized by staying indoors during most of the day. Furthermore, the ambient UV radiation is mitigated by shadowing by buildings. The aim of the study was to find out activities which may contribute to UV-induced health risk in a low exposure environment. Exposure was measured during typical outdoor activities: shopping, walking, sitting in a sidewalk café, cycling, sightseeing and at an open-air pool (solar elevation: 10°,70°). Measurements were taken with an optoelectronic device which was fixed on the chest. Besides the UV Index we used the sun burn time (SBT) for risk assessments. Generalization of our results was made by calculating ratios of personal exposure to the ambient UV radiation. UV exposure was by far the highest when our study subject stayed at the swimming pool. The SBT was around 30 min for melano-compromised skin type. For all other activities, except shopping, the SBT range up to 1 h. With respect to photodamage we found that at high solar elevation (>45°) photoprotective measures should be applied for certain activities even within a city. [source] A novel growth method for ZnAl2O4 single crystalsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 3 2006K. Kumar Abstract ZnAl2O4 is a well-known wide band gap compound semiconductor (Eg=3.8eV), ceramic, opto-mechanical, anti-thermal coating in aero-space vehicles and UV optoelectronic devices. A novel method for the growth of single crystals of a ternary oxide material was developed as a fruit of a long term work. Material to be grown as metal incorporated single crystal was taken as precursor and put into a bath containing acid as reaction speed up reagent (catalyst) as well as solvent with a metal foil as cation scavenger. Using this method, ZnAl2O4 crystals having hexagonal facets are prepared from a single optimized bath. Structural and compositional properties of crystals were studied using Philips, Xpert - MPD: X-ray diffractometer and Philips, ESEM-TMP + EDAX. Thus technique was found to be a new low cost and advantageous method for growth of single crystals of ternary oxide a material. We hope that these data be helpful either as a scientific or technical basis in material processing. Dedicated to Prof. P. Ramasamy © 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim [source] Structural Fabrication and Functional Modulation of Nanoparticle,Polymer CompositesADVANCED FUNCTIONAL MATERIALS, Issue 10 2010Hao Zhang Abstract This review article summarizes recent progress in the fabrication methodologies and functional modulations of nanoparticle (NP),polymer composites. On the basis of the techniques of NP synthesis and surface modification, the fabrication methods of nanocomposites are highlighted; these include surface-initiated polymerization on NPs, in situ formation of NPs in polymer media, and the incorporation through covalent linkages and supramolecular assemblies. In these examples, polymers are foremost hypothesized as inert hosts that stabilize and integrate the functionalities of NPs, thus improving the macroscopic performance of NPs. Furthermore, due to the unique physicochemical properties of polymers, polymer chains are also dynamic under heating, swelling, and stretching. This creates an opportunity for modulating NP functionalities within the preformed nanocomposites, which will undoubtedly promote the developments of optoelectronic devices, optical materials, and intelligent materials. [source] Customized Electronic Coupling in Self-Assembled Donor,Acceptor NanostructuresADVANCED FUNCTIONAL MATERIALS, Issue 22 2009Dimas G. de Oteyza Abstract Charge transfer processes between donor,acceptor complexes and metallic electrodes are at the heart of novel organic optoelectronic devices such as solar cells. Here, a combined approach of surface-sensitive microscopy, synchrotron radiation spectroscopy, and state-of-the-art ab initio calculations is used to demonstrate the delicate balance that exists between intermolecular and molecule,substrate interactions, hybridization, and charge transfer in model donor,acceptor assemblies at metal-organic interfaces. It is shown that charge transfer and chemical properties of interfaces based on single component layers cannot be naively extrapolated to binary donor,acceptor assemblies. In particular, studying the self-assembly of supramolecular nanostructures on Cu(111), composed of fluorinated copper-phthalocyanines (F16CuPc) and diindenoperylene (DIP), it is found that, in reference to the associated single component layers, the donor (DIP) decouples electronically from the metal surface, while the acceptor (F16CuPc) suffers strong hybridization with the substrate. [source] Selective Angle Electroluminescence of Light-Emitting Diodes based on Nanostructured ZnO/GaN HeterojunctionsADVANCED FUNCTIONAL MATERIALS, Issue 21 2009Hang-Kuei Fu Abstract Selective angle electroluminescence of violet light with a peak wavelength of 405,nm from light-emitting diodes based on nanostructured p-GaN/ZnO heterojunctions is reported. The fabrication of well-aligned nanobottles with excellent crystalline quality is achieved by chemical vapor deposition at temperatures as low as 450,°C with a specially designed upside-down arrangement of substrate configuration. Selective angle light sources are essential in our daily life. With the geometry of the nanobottle waveguides, it is very easy to realize such a practical application. Therefore, the discovery reported here should be very useful for the future development of many unique optoelectronic devices. [source] One-Dimensional Microwires Formed by the Co-Assembly of Complementary Aromatic Donors and AcceptorsADVANCED FUNCTIONAL MATERIALS, Issue 11 2009Jie-Yu Wang Abstract A truxene derivative (Tr3) with a C3 symmetric conjugated plane is synthesized; this derivative is a perfect match, in both size and structure, with its oxidized counterpart, the truxenone derivative (TrO3), a new electron acceptor that was recently reported. The complementary pair, Tr3 and TrO3, sets a good platform for the investigation of aromatic donor,acceptor interactions. Detailed 1H NMR experiments, photoluminescence spectroscopy, as well as differential scanning calorimetry are performed to investigate the interaction between Tr3 and TrO3, from solution to mesophase. One-dimensional microbelts readily formed from a 1:1 mixture of Tr3 and TrO3. Scanning electron microscopy, powder X-ray diffraction, as well as fluorescence microscopy are performed to elucidate their co-assembly structure in the solid state. Moreover, modulation of the co-assembly structure is easily realized by changing the concentration or mixing ratio. The present system opens the possibility of forming 1D heterostructures via electron donor,acceptor interaction, and its potential application as P,N junction and photowaveguide materials in optoelectronic devices. [source] Conducting-Polymer Nanomaterials for High-Performance Sensor Applications: Issues and ChallengesADVANCED FUNCTIONAL MATERIALS, Issue 10 2009Hyeonseok Yoon Abstract Owing to their promising applications in electronic and optoelectronic devices, conducting polymers have been continuously studied during the past few decades. Nevertheless, only limited progress had been made in conducting-polymer-based sensors until nanostructured conducting polymers were demonstrated for high-performance signal transducers. Significant advances in the synthesis of conducting-polymer nanomaterials have been recently reported, with enhanced sensitivity relative to their bulk counterparts. Today, conducting-polymer nanomaterials rival metal and inorganic semiconductor nanomaterials in sensing capability. However, there are still several technological challenges to be solved for practical sensor applications of conducting-polymer nanomaterials. Here, the key issues on conducting-polymer nanomaterials in the development of state-of-the-art sensors are discussed. Furthermore, a perspective on next-generation sensor technology from a materials point of view is also given. [source] Field Emission and Cathodoluminescence of ZnS Hexagonal Pyramids of Zinc Blende Structured Single CrystalsADVANCED FUNCTIONAL MATERIALS, Issue 3 2009Zhi-Gang Chen Abstract Single-crystal hexagonal pyramids of zinc blende ZnS are fabricated by facile thermal evaporation in an ammonia atmosphere at 1150,°C. It is found that ZnS pyramids grow along the [111] crystal axis and possess a sharp tip with a diameter of ,10,nm and a micrometer-sized base. The structural model and growth mechanism are proposed based on crystallographic characteristics. This unique ZnS pyramid structure exhibits a low turn-on field (2.81,V µm,1), a high field-enhancement factor (over 3000), a large field-emission current density (20,mA cm,2), and good stability with very small fluctuation (0.9%). These superior field-emission properties are clearly attributed to the pyramid morphology, with micrometer-sized bases and nanotips, and high crystallinity. Moreover, a stable UV emission of 337,nm at room temperature is observed and can be ascribed to the band emission of the zinc blende phase. These results suggest that the ZnS hexagonal pyramids can be expected to find promising applications as field emitters and optoelectronic devices. [source] High Purity GaAs Nanowires Free of Planar Defects: Growth and Characterization,ADVANCED FUNCTIONAL MATERIALS, Issue 23 2008Hannah J. Joyce Abstract We investigate how to tailor the structural, crystallographic and optical properties of GaAs nanowires. Nanowires were grown by Au nanoparticle-catalyzed metalorganic chemical vapor deposition. A high arsine flow rate, that is, a high ratio of group V to group III precursors, imparts significant advantages. It dramatically reduces planar crystallographic defects and reduces intrinsic carbon dopant incorporation. Increasing V/III ratio further, however, instigates nanowire kinking and increases nanowire tapering. By choosing an intermediate V/III ratio we achieve uniform, vertically aligned GaAs nanowires, free of planar crystallographic defects, with excellent optical properties and high purity. These findings will greatly assist the development of future GaAs nanowire-based electronic and optoelectronic devices, and are expected to be more broadly relevant to the rational synthesis of other III,V nanowires. [source] Structural Characterization of Multi-Quantum Wells in Electroabsorption-Modulated Lasers by using Synchrotron Radiation Micrometer-BeamsADVANCED MATERIALS, Issue 18 2010Lorenzo Mino Advanced optoelectronic devices require monolithic integration of different functions at chip level. This is the case of multi-quantum well (MQW) electro absorption modulated lasers (EMLs) realized by using the selective area growth (SAG) technique, and which can be employed in long-distance, high-frequency optical fiber communication applications. We demonstrate that a micrometer-resolved X-ray beam available at third-generation synchrotron radiation sources allows direct measurement of determinant structural parameters of MQW EML structures. [source] Coaxial Metal Nano-/Microcables with Isolating Sheath: Synthetic Methodology and Their Application as InterconnectsADVANCED MATERIALS, Issue 17 2010Min-Rui Gao Abstract Synthesis of coaxial nano-/microcables has been an intensive research subject due to their heterogeneous structures, tuneable properties, and important applications in nano-/micrometer-scale electronic and optoelectronic devices. Research on the fabrication of nanocables via solution strategies has made great progress in the past few years. In this Research News article, rapidly emerging new solution strategies such as hydrothermal carbonization (HTC) and synergistic soft,hard templates (SSHTs) are highlighted. Unique and flexible coaxial nano-/microcables synthesized by those methods have obvious advantages such as long-term stability and their electrical transport properties, compared with bare counterparts, suggesting that they are potential candidates as interconnects in the future. [source] Aqueous-Processable Noncovalent Chemically Converted Graphene,Quantum Dot Composites for Flexible and Transparent Optoelectronic FilmsADVANCED MATERIALS, Issue 5 2010Xiumei Geng The preparation and optoelectronic response of flexible composites via noncovalent coupling of quantum dots to chemically converted graphene is presented. The photoinduced charge transfer is confirmed by photoconductivity measurements and the photosensitivity is improved with increasing loadings of quantum dots. This opens up a new effective route to form composites for future large-area flexible and transparent optoelectronic devices. [source] Controlled Growth of High-Quality ZnO-Based Films and Fabrication of Visible-Blind and Solar-Blind Ultra-Violet DetectorsADVANCED MATERIALS, Issue 45 2009Xiaolong Du Abstract ZnO is a wide-bandgap (3.37,eV at room temperature) oxide semiconductor that is attractive for its great potential in short-wavelength optoelectronic devices, in which high quality films and heterostructures are essential for high performance. In this study, controlled growth of ZnO-based thin films and heterostructures by molecular beam epitaxy (MBE) is demonstrated on different substrates with emphasis on interface engineering. It is revealed that ultrathin AlN or MgO interfacial layers play a key role in establishing structural and chemical compatibility between ZnO and substrates. Furthermore, a quasi-homo buffer is introduced prior to growth of a wurtzite MgZnO epilayer to suppress the phase segregation of rock-salt MgO, achieving wide-range bandgap tuning from 3.3 to 4.55,eV. Finally, a visible-blind UV detector exploiting a double heterojunction of n-ZnO/insulator-MgO/p-Si and a solar-blind UV detector using MgZnO as an active layer are fabricated by using the growth techniques discussed here. [source] Conjugated-Polymer Blends for OptoelectronicsADVANCED MATERIALS, Issue 38-39 2009Christopher R. McNeill Abstract Solution-processed polymer optoelectronic devices such as light-emitting diodes and solar cells have many advantages for large-area manufacture, and show increasing levels of performance. Here, we review recent progress in using blends of two conjugated polymers for optoelectronic devices. The blending of two or more polymers allows tuning of device performance, and for photovoltaics presents an attractive way to combine donor and acceptor materials with a morphology controlled by polymer phase separation. We discuss recent advances in imaging the microstructure of conjugated polymer blends, and we demonstrate how the blend structure leads to performance advantages in both LEDs and photovoltaic devices. [source] Al2O3/ZrO2 Nanolaminates as Ultrahigh Gas-Diffusion Barriers,A Strategy for Reliable Encapsulation of Organic ElectronicsADVANCED MATERIALS, Issue 18 2009Jens Meyer Highly efficient gas-diffusion barriers based on nanolaminates of alternating Al2O3 and ZrO2 layers grown at 80,°C by atomic-layer deposition are presented. Ultralow water-vapor permeation rates are reported, and a dramatic reduction of statistical defects on larger areas was found compared to single Al2O3 layers. This study provides a concept for the encapsulation of organic optoelectronic devices. [source] Magnetic-Field Effects in Organic Semiconducting Materials and DevicesADVANCED MATERIALS, Issue 14-15 2009Bin Hu Abstract It has been experimentally discovered that a low magnetic field (less than 500 mT) can substantially change the electroluminescence, photoluminescence, photocurrent, and electrical-injection current in nonmagnetic organic semiconducting materials, leading to magnetic-field effects (MFEs). Recently, there has been significant driving force in understanding the fundamental mechanisms of magnetic responses from nonmagnetic organic materials because of two potential impacts. First, MFEs can be powerful experimental tools in revealing and elucidating useful and non-useful excited processes occurring in organic electronic, optical, and optoelectronic devices. Second, MFEs can lead to the development of new multifunctional organic devices with integrated electronic, optical, and magnetic properties for energy conversion, optical communication, and sensing technologies. This progress report discusses magnetically sensitive excited states and charge-transport processes involved in MFEs. The discussions focus on both fundamental theories and tuning mechanisms of MFEs in nonmagnetic organic semiconducting materials. [source] Directed Assembly of Polymer Blends Using Nanopatterned TemplatesADVANCED MATERIALS, Issue 7 2009Ming Wei The direct assembly of polymer blends on chemically functionalized surfaces is shown to produce a variety of nonuniform complex patterns. This method provides a powerful tool for easily producing nonuniform patterns in a rapid (30 s), one-step process with high specificity and selectivity for a variety of applications, such as nanolithography, polymeric optoelectronic devices, integrated circuits, and biosensors. [source] A Photosynthetic Reaction Center Covalently Bound to Carbon Nanotubes,ADVANCED MATERIALS, Issue 22 2007I. Carmeli The photosystem reaction center I is covalently bound to carbon nanotubes using carbodiimide chemistry. The hybrid systems are characterized by atomic force microscopy, and UV-VIS spectroscopy, indicating a high degree of conjugation between the photosystem reaction center and the carbon nanotubes. Three different architectures for optoelectronic circuits are presented, which have the potential to serve as basis for molecular optoelectronic devices. [source] Fluorene-based materials and their supramolecular propertiesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2009Robert Abbel Abstract Fluorene-based ,-conjugated polymers and oligomers combine several advantageous properties that make them well-suited candidates for applications in organic optoelectronic devices and chemical sensors. This review highlights strategies to synthesize these materials and to tune their absorption and emission colors. Furthermore, methods to control their supramolecular organization will be discussed. In many cases, a delicate interplay between the chemical structure and the processing conditions are found, resulting in a high sensitivity of both structural features and optical properties. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4215,4233, 2009 [source] PEDOT:Poly(1-vinyl-3-ethylimidazolium) dispersions as alternative materials for optoelectronic devicesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2008Cristina Pozo-Gonzalo PEDOT formulations in acetonitrile have been synthesised using a phase transfer reaction involving two steps; being a polymerization in water and then a subsequent coagulation of the corresponding PEDOT by anion exchange. The strategy followed is to synthesise organic formulations using a less acidic stabilizer and fine-tuned hydrophobic properties which are suitable for using in OLEDs as a HTL (hole transport layer), leading to an interesting starting point for OLED applications. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.] [source] Energy Transfer Enables 1.53 ,m Photoluminescence from Erbium-Doped TiO2 Semiconductor Nanocrystals Synthesized by Ar/O2 Radio-Frequency Thermal PlasmaJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2008Ji-Guang Li Highly crystalline, highly luminescent nanopowders of Er3+ -doped TiO2 have been successfully synthesized via one-step Ar/O2 radio-frequency thermal plasma processing. Energy transfer from the TiO2 host to Er3+ activators has been confirmed by combined means of UV-vis, excitation, and photoluminescence spectroscopies. As a consequence, bright photoluminescence at ,1.53 ,m was observed from the nanopowders either by directly exciting the Er3+ activator or by exciting the TiO2 host lattice. A comparative study shows that the nanopowder of the same system made via coprecipitation lacks the energy transfer. The plasma-generated nanopowders may thus find applications in optoelectronic devices. [source] Syntheses of New 3,6-Carbazole-Based Donor/Acceptor Conjugated Copolymers for Optoelectronic Device ApplicationsMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 18 2010Mei-Hsiu Lai Abstract The syntheses, properties, and optoelectronic device characteristics of four new 3,6-carbazole-based donor/acceptor conjugated copolymers are reported. Such copolymers are used to explore the effects of acceptor strength and backbone coplanarity on the electronic and optoelectronic properties. The optical bandgaps of the studied copolymers are PCzQ (2.29,eV),>,PCzDTQ (1.91,eV),>,PCzTP (1.75,eV),>,PCzDTTP (1.49,eV), which are much smaller than the parent poly(3,6-carbazole). The power conversion efficiency of the photovoltaic cells fabricated from blends of copolymer/PC61BM or PC71BM reached 1.01 and 1.73% by varying the film thickness or blend ratio. The experimental results suggest the potential application of 3,6-carbazole acceptor conjugated copolymers in optoelectronic devices. [source] Synthesis and Study of CdS Nanoparticle-Doped Poly(1,4-dihexyloxybenzene)MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 4 2008Gouri Sankar Paul Abstract A simple, economical and high yielding method to prepare poly(1,4-dihexyloxybenzene), an alkylated derivative of poly(para -phenylene) (PPP), is reported. We further prepared a composite of poly(1,4-dihexyloxybenzene) and CdS nanoparticles and studied their structural, optical, stability and transport properties. It was observed that the conductivity of poly(1,4-dihexyloxybenzene) increased by several orders of magnitude when doped with CdS nanoparticles. Similarly, CdS nanoparticle-doped PPP showed higher thermal stability, when compared to the neat polymer. As these composites could be processed in the same way as organic polymers, they would find applications in many low-cost optoelectronic devices. [source] Orientation and Dynamics of ZnO Nanorod Liquid Crystals in Electric FieldsMACROMOLECULAR RAPID COMMUNICATIONS, Issue 12 2010Matthias Zorn Abstract ZnO nanorod polymer hybrids (i.e., ZnO nanorods coated with a block copolymer with a short anchor block (dopamine) and a longer solubilizing block of polystyrene (PS)) form liquid crystalline (LC) phases if they are dispersed at high concentration e.g., in a PS oligomer matrix. Due to the high mobility of the low Tg -matrix the nanorod polymer hybrids show a switching behavior under an applied AC electric field. Hence, the orientation of the nanorod mesogens can be changed from planar (parallel to the substrate) to homeotropic (perpendicular) in full analogy to the switching of low molecular liquid crystals in an electric field. Dielectric measurements show that such a switching is mainly due to the cooperative LC behavior, because the rods themselves exhibit only a very small effective dipole moment. The process can be investigated by polarizing microscopy. SEM images show the orientations of the individual nanorods, which correspond to the Fredericks transition well known for liquid crystals aligned in an electric field. This was the first time such a transition could be visualized by electron microscopy due to the large nanorod mesogens. The observation is interesting to orient nanorods perpendicular to an electrode and can help to improve optoelectronic devices. [source] Promising Optoelectronic Materials: Polymers Containing Phosphorescent Iridium(III) ComplexesMACROMOLECULAR RAPID COMMUNICATIONS, Issue 9-10 2010Qiang Zhao Abstract As one of the most promising optoelectronic materials, polymers that contain phosphorescent IrIII complexes have attracted more and more interest in recent years. They are a class of well-known electroluminescent materials with excellent performance. So far, efficient green-, red-, and white-emitting polymer light-emitting diodes based on polymers with on-chain IrIII complexes have been realized successfully. For the realization of this class of polymer material, IrIII complexes (as energy guest) can be introduced into the main-chain or side-chain of polymers (as energy host). In this article, we summarize the design principles, synthetic routes, structure,property relationships, and applications in optoelectronic devices of polymers that contain phosphorescent IrIII complexes. [source] Photonic bandgap modification in hollow optical fibers integrated with single walled carbon nanotubesMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 11 2009Marco Pisco Abstract Single-walled carbon nanotubes (SWCNTs) have been infiltrated within the holes of hollow-core optical fibers (HOFs) by Langmuir-Blodgett method in order to develop new in-fiber active and passive optoelectronic devices. Far field transmission characterizations demonstrated HOF's holes successful filling and the SWCNTs' capability to modify the guiding properties of HOFs. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2729,2732, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24725 [source] | |||||||||||||||||||||||||||||||