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Optoelectronic Applications (optoelectronic + application)
Selected AbstractsSynthetic Strategies for Hybrid Materials to Improve Properties for Optoelectronic Applications,ADVANCED FUNCTIONAL MATERIALS, Issue 14 2008Olga García Abstract We report, for the first time to the best of our knowledge, a systematic study to relate the laser action from BODIPY dyes, doped into monolithic hybrid matrices, with the synthetic protocols of the final materials prepared via sol-gel. To this aim, the influence of both the hydrolysis time, increased in a controlled way, and the nature of the neutralization agent (pyridine, 3-amino-propyltriethoxy-silane (APS), N -[3-(trimethoxysilyl)propyl]-ethylene diamine (TSPDA), and N1 -[3-(trimethoxysilyl)propyl]- diethylene triamine (TSPTA) on the laser action of PM567, incorporated into hybrid matrices based on copolymers of methyl methacrylate (MMA) and 2-hydroxyethyl methacrylate (HEMA), with methyltriethoxysilane (TRIEOS) as inorganic precursor, was analyzed. The presence of the amine-modified silane TSPDA as neutralization agent, which is able at the same time to be anchored to the inorganic network enhancing the inorganic-organic compatibility through the matrix interphase, and utilization of hydrolysis times lower than 10 minutes, increased significantly the lasing efficiency and photostability of dye. The extension of this study to the laser behavior of BODIPY dyes embedded in other different hybrid materials based on hydrolyzed-condensed copolymers of MMA with 3-(trimethoxysilyl)propyl methacrylate (TMSPMA) in a 1/1 volumetric proportion, validates the generalization of the above conclusions, which provide guides for the optimization of the synthesis of organic-inorganic hybrid materials with optoelectronic innovative applications independently of their composition. [source] A Conjugated Polymer for Near Infrared Optoelectronic Applications,ADVANCED MATERIALS, Issue 20 2007E. Perzon A new conjugated polymer, LBPP-1, with an unusually low band-gap (ca.,1.0,eV) is presented. Light absorption and photovoltaic response up to 1200,nm in composites with a fullerene is demonstrated. Solar cell performance is presented and the polymer's suitability for photodetection in the infrared region is discussed. [source] Chemically Directed Assembling of Functionalized Luminescent Nanocrystals onto Plasma Modified Substrates Towards Sensing and Optoelectronic ApplicationsPLASMA PROCESSES AND POLYMERS, Issue S1 2009Eloisa Sardella Abstract In this work semiconductor nanocrystals (NCs) were assembled by means of a layer-by-layer procedure, by properly combining RF (13.56,MHz) glow discharge-assisted processes with wet chemistry approaches. Colloidal core shell type NCs formed by CdSe coated with an epitaxial layer of ZnS (CdSe@ZnS) were then assembled, from aqueous solution, onto the plasma modified materials. The obtained results show that spatially resolved NC assembling can be successfully achieved on micro-structured domains obtained by means of plasma assisted processes. Layers of functionalized NCs are thus demonstrated to be materials that can be effectively integrated into devices for application in photovoltaics, electronic nano-devices and biological sensors. [source] Thermally reversible materials based on thermosetting systems modified with polymer dispersed liquid crystals for optoelectronic application,POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 11-12 2006A. Tercjak Abstract The main aim of this research was the generation of new intelligent materials, in this case thermoreversible material, based on an epoxy matrix modified with liquid crystal for optoelectronic application. The samples were prepared by the reaction-induced phase separation (RIPS) of a solution of 4,-(hexyloxy)-4-biphenyl-carbonitrile (HOBC) and polystyrene (PS) in diglicydylether of bisphenol-A epoxy resin (DGEBA). The systems were cured with a stoichiometric amount of an aromatic amine hardener, 4,4,-methylene bis(3-chloro-2,6-diethylaniline) (MCDEA). Taken into account results obtained by differential scanning calorimetry (DSC) and transmission optical microscopy (TOM) equipped with a hot stage it was found that depending on morphology generated by RIPS of HOBC/thermoplastic particles in the epoxy matrix thermally reversible light scattering (TRLS) material can be obtained. Copyright © 2006 John Wiley & Sons, Ltd. [source] Interface Modifications of InAs Quantum-Dots Solids and their Effects on FET PerformanceADVANCED FUNCTIONAL MATERIALS, Issue 6 2010Michal Soreni-Harari Abstract InAs nanocrystals field-effect transistors with an ON/OFF ratio of 105 are reported. By tailoring the interface regions in the active layer step-by-step, the evolution of the ON/OFF ratio can be followed from approximately 5 all the way to around 105. The formation of a semiconducting solid from colloidal nanocrystals is achieved through targeted design of the nanocrystal,nanocrystal interaction. The manipulation characteristics of the nanocrystal interfaces include the matrix surrounding the inorganic core, the interparticle distance, and the order of nanocrystals in the 3D array. Through careful analysis of device characteristics following each treatment, the effect of each on the physical properties of the films are able to be verified. The enhanced performance is related to interparticle spacing, reduction in sub-gap states, and better electronic order (lower , parameter). Films with enhanced charge transport qualities retain their quantum-confined characteristics throughout the procedure, thus making them useful for optoelectronic applications. [source] Ultrasmooth, Large-Area, High-Uniformity, Conductive Transparent Single-Walled-Carbon-Nanotube Films for Photovoltaics Produced by Ultrasonic SprayingADVANCED MATERIALS, Issue 31 2009Robert C. Tenent Single-walled-carbon-nanotube (SWNT) films are prepared with high transparency, electrical conductivity, and uniformity, with exceptionally low surface roughness, on arbitrarily large substrates by ultrasonic spraying. This scalable process is ideally suited for large-area, solution-based production of SWNT electrodes for photovoltaics and other optoelectronic applications. [source] Growth of Silicon Oxide in Thin Film Block Copolymer Scaffolds,ADVANCED MATERIALS, Issue 8 2004H. Kim Thin films of asymmetric diblock copolymers have been used as scaffolds to define an ordered array of nanometer-scale reaction vessels in which high density arrays of silicon oxide nanostructures (see Figure) are produced by exposure to silicon tetrachloride. Such site-specific silicon oxide nanostructures could have widespread uses for sensory and optoelectronic applications. [source] Host copolymers containing pendant carbazole and oxadiazole groups: Synthesis, characterization and optoelectronic applications for efficient green phosphorescent OLEDsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 15 2008Kun-Ming Yeh Abstract Vinyl copolymers (PCOn), containing pendant carbazole and aromatic 1,3,4-oxadiazole attached with dodecyloxy group, were prepared from their corresponding precursor poly(9-vinyl carbazole- co -4-vinylbenzyl chloride) (PCBn) by the Williamson condensation (n: mole% of 4-vinylbenzyl chloride). These copolymers were used as host materials for green phosphorescent light-emitting diodes after blending 4 wt % of Ir(ppy)3. PL spectra of the PCOn films showed the formation of excimer or exciplex. The phosphorescent EL devices were fabricated with a configuration of ITO/PEDOT:PSS/host copolymers:Ir(ppy)3/BCP/Ca/Al. The PL and EL spectra of the blends [PCOn:Ir(ppy)3] revealed dominant green emission at 517 nm attributed to Ir(ppy)3 due to efficient energy transfer from the host to Ir(ppy)3. Efficient green phosphorescent OLEDs was obtained when employing copolymer PCO16 as the host and Ir(ppy)3 as the guest. The maximal luminance efficiency and the maximal luminance of this device were 17.9 cd/A and 19,903 cd/m2, respectively. After doped with Ir(ppy)3, the morphology of the films, both controlled PCO20 and PCO20 with attached dodecyloxy groups, were investigated by tapping-mode AFM and FE-SEM. The film of PCO20 exhibited uniform, featureless image and showed much better device performance than PCO20, which have been attributed to good compatibility of PCO20 with Ir(ppy)3. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5180,5193, 2008 [source] Preparation and Cathodoluminescence of Mg-Doped and Zn-Doped GaN PowdersJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2008Hui-Li Li In this paper, undoped, Mg- and Zn-doped gallium nitride powders were prepared by direct nitridation of Ga2O3 under a flowing NH3 gas. The phase purity, morphology and cathodoluminescence spectra were presented. The Ga2O3 powders can be completely nitridized to GaN at 1000°C. The resultant GaN powders agglomerated together with submicron-sized polyhedral crystals. At room temperature, the Mg- and Zn-doped powders exhibit bright blue-violet emission at around 3.05 and 2.81 eV, respectively. This provides clear evidence that magnesium or zinc is incorporated into the GaN powders as an acceptor and suggests that the luminescent materials are promising candidates for optoelectronic applications. [source] Polymerizable Well-Defined Oligo(thiophene amide)s and their ROMP Block CopolymersMACROMOLECULAR RAPID COMMUNICATIONS, Issue 14 2009Stefan Hilf Abstract We report the synthesis of conjugated thiophene amide oligomers that constitute a new class of chromophores with potential for optoelectronic applications. The synthesis of defined norbornene-substituted oligothiophene amides using conventional coupling chemistry is described. Their electronic properties depend on the degree of oligomerization as UV/Vis and fluorescence spectroscopy demonstrate. A significant red shift in the spectra upon an increase in the oligomer length evidences conjugation of the thiophene rings via the amide linkages. ROMP of the norbornene-substituted oligomers gives homopolymers and block-copolymers with a solubilizing second block. The amphiphilic character of the block copolymers is used to study micellization and bulk self-organization. [source] Compensation of native defects in PbTe and Pb1,xSnx TePHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 1 2008V. N. Babentsov Abstract Semi-insulation of the narrow-gap IV,VI semiconductor compounds PbTe and Pb1,xSnx Te used for infrared optoelectronic applications was investigated technologically and theoretically. Practically important cases in which the concentration of native defects greatly exceeds the intrinsic concentra- tion of free carriers due to the growth conditions are discussed. In particular, doping conditions for the semi-insulation are determined for Cd, In and Ga compensating impurities. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Low-temperature MBE-grown GaBiAs layers for terahertz optoelectronic applicationsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2009Vaidas Pa, ebutas Abstract Gallium bismide arsenide epitaxial layers were grown by molecular-beam-epitaxy at low substrate temperatures and investigated for their suitability in terahertz optoelectronic applications. Optical pump-terahertz probe measurements on these layers have shown that carrier dynamics can be described using two characteristic times. The faster decay component has characteristic times shorter than 1 ps, whereas the slower component decays in several tens of picoseconds. Fitting the electron lifetimes dependence on optical excitation level the electron trapping cross-section and trap density were determined. The possible mechanism of carrier recombination was discussed. The photoconductive terahertz emitters and detectors made from GaBiAs layers have been manufactured and used in time-domain spectroscopy system with a signal bandwidth larger than 4.5 THz. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Nanoindentation response of compound semiconductorsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 8 2007E. Le Bourhis Abstract The paper reviews the nanoindentation behaviour of III-V semiconductors under concentrated load and its implication for optoelectronic-device design. We consider first, fundamental aspects involved into the mechanical resistance to contact loading of semiconductor single crystals (elastic-plastic transition, indentation strain, hardness-yield relationship). The paper then describes recent applicative studies aimed at improving the heterostructure quality used in optoelectronic applications and emphasizes the so-called mechanical design (alloying and compliant substructure). (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Collaborative Research Centre of the Deutsche Forschungsgemeinschaft Semiconductor Nanometer Devices Fundamentals , Concepts , RealisationsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 8 2004Markus C. Amann This Special Issue is a collection of Review Articles written by the members of the Collaborative Research Centre (SFB) 348 of the German Research Foundation (DFG). Its aims were the development of new methods for nanometer-scale structuring of semiconductors, the experimental and theoretical investigations of such nanostructures, and the design and prototyping of novel devices for high frequency, optical and optoelectronic applications. This required coordinated research efforts by physicists and electrical engineers into both basic physical phenomena and device oriented questions. [source] Nanocomposites of silver nanoparticle and dinonylnaphthalene disulfonic acid-doped thermoreversible polyaniline gelPOLYMER ENGINEERING & SCIENCE, Issue 3 2010Ashesh Garai Silver/polyaniline-dinonylnaphthalene disulfonic acid (PANI-DNNDSA) gel nanocomposites are prepared from the reduction of silver salt by polyaniline in formic acid medium. Scanning electron micrographs (SEM) indicate the presence of three-dimensional fibrillar network structure and the silver nanoparticles remain dispersed within the PANI-DNNDSA fibrillar network. Differential scanning calorimetric (DSC) study shows reversible first-order phase transition characterizing the composite to behave as a thermoreversible gel. Transmission electron micrographs (TEM) show a decrease of nanoparticle size with increasing AgNO3 concentration. Wide angle X-ray scattering (WAXS) patterns show lamellar structure in the gel as well as in the gel metal nanocomposites (GMNCs) and the two melting peaks in the DSC patterns correspond to the melting of monolayer and bilayer crystals produced from the interdigitation of DNNDSA tails anchored from PANI chains within the PANI lamella. The above melting points are greater in the GMNCs than that of pure gel indicating the formation of complex melting thermogram with crystallites produced from the anchored surfactants tails at the surface of Ag nanoparticles. The GMNCs show a higher thermal stability than that of pure PANI-DNNDSA gel. PANI-DNNDSA gel has an emission peak at 354 nm but fluorescence quenching occurs in the GMNCs and the emission peak becomes red shifted. Also in the UV,vis spectra the , band-polaron band transition peak shows a red shift and the DC conductivity increases with increasing Ag nanoparticle concentration in the GMNCs. The current (I),voltage (V) characteristic curves indicate Ohmic nature of conductivity of the gel and the current at the same voltage increases appreciably with increasing Ag nanoparticle concentration. These GMNCs are easily processible due to its thermoreversible nature. So, an easily processible, thermally stable and highly conducting DNNDSA-doped PANI-Ag gel nanocomposite with interesting photoluminescent property has been successfully developed suitable for optoelectronic applications. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers [source] Long-term Reliability Prediction of 935 nm LEDs Using Failure Laws and Low Acceleration Factor Ageing TestsQUALITY AND RELIABILITY ENGINEERING INTERNATIONAL, Issue 6 2005Y. Deshayes Abstract Numerous papers have already reported various results on electrical and optical performances of GaAs-based materials for optoelectronic applications. Other papers have proposed some methodologies for a classical estimation of reliability of GaAs compounds using life testing methods on a few thousand samples over 10,000 hours of testing. In contrast, fewer papers have studied the complete relation between degradation laws in relation to failure mechanisms and the estimation of lifetime distribution using accelerated ageing tests considering a short test duration, low acceleration factor and analytical extrapolation. In this paper, we report the results for commercial InGaAs/GaAs 935 nm packaged light emitting diodes (LEDs) using electrical and optical measurements versus ageing time. Cumulative failure distributions are calculated using degradation laws and process distribution data of optical power. A complete methodology is described proposing an accurate reliability model from experimental determination of the failure mechanisms (defect diffusion) for this technology. Electrical and optical characterizations are used with temperature dependence, short-duration accelerated tests (less than 1500 h) with an increase in bias current (up to 50%), a small number of samples (less than 20) and weak acceleration factors (up to 240). Copyright © 2005 John Wiley & Sons, Ltd. [source] Synthesis and Properties of DNA Complexes Containing 2,2,6,6-Tetramethyl-1-piperidinoxy (TEMPO) Moieties as Organic Radical Battery MaterialsCHEMISTRY - A EUROPEAN JOURNAL, Issue 11 2008Jinqing Qu Dr. Abstract We report here the first example of organic radical battery with DNA. Though there is a growing interest in DNA/cationic-lipid complexes as promising gene delivery vehicles, few efforts have been focused on the use of such complexes as advanced materials for organic optoelectronic applications. The present article describes how substitution of the sodium counter cation of DNA with cationic amphiphilic lipid(1,4) provided novel DNA,lipid complexes that contain TEMPO radicals, in which the actual mole ratio of phosphate to lipid was 1:0.84 to 1:0.16. All the TEMPO-containing DNA,lipid complexes displayed reversible two-stage charge/discharge processes, the discharge capacities of which were 40.5,60.0,A,h,kg,1. In particular, the capacity of a DNA,lipid(3)-based cell reached 60.0,A,h,kg,1, which corresponds to 192,% relative to its theoretical value for the single-electron one-stage process, indicating a two-electron process. [source] | ||||||||||||||||||||||||||||