Home About us Contact
|
Home About us Contact | ||
|
|
||
Transport Layer (transport + layer)
Kinds of Transport Layer Selected AbstractsImproved Photovoltaic Performance of Heterostructured Tetrapod-Shaped CdSe/CdTe Nanocrystals Using C60 InterlayerADVANCED MATERIALS, Issue 44 2009Yanqin Li Photovoltaic (PV) devices based on CdSe/CdTe-C60 active layers, in which the nanocrystal and fullerene (C60) layers work as electron-donor and electron-acceptor/transport layers, respectively, were fabricated. Efficiencies up to 0.62% were reached in the hybrid cells. The PV performance was greatly improved with respect to that of CdSe/CdTe-P3HT- and CdSe/CdTe-based devices, fabricated as reference. [source] Cover Picture: Multilayer Polymer Light-Emitting Diodes: White-Light Emission with High Efficiency (Adv. Mater.ADVANCED MATERIALS, Issue 17 200517/2005) Abstract White-light-emitting polymer diodes can be fabricated by solution processing using a blend of luminescent semiconducting polymers and organometallic complexes as the emission layer, and water-soluble (or ethanol-soluble) polymers and/or small molecules as the hole-injection/transport layer (HIL/HTL) and the electron injection/transport layer (EIL/ETL), as reported on p.,2053 by Gong, Bazan, Heeger and co-workers. Illumination-quality light is obtained from these multilayer, high-performance devices, with stable CIE coordinates, color temperatures, and high color-rendering indices all close to those of "pure" white light. The cover illustration envisages the incorporation of the fabrication technique with low-cost manufacturing technology in order to produce large areas of high-quality white light. [source] The Role of Transition Metal Oxides in Charge-Generation Layers for Stacked Organic Light-Emitting DiodesADVANCED FUNCTIONAL MATERIALS, Issue 11 2010Sami Hamwi Abstract The mechanism of charge generation in transition metal oxide (TMO)-based charge-generation layers (CGL) used in stacked organic light-emitting diodes (OLEDs) is reported upon. An interconnecting unit between two vertically stacked OLEDs, consisting of an abrupt heterointerface between a Cs2CO3 -doped 4,7-diphenyl-1,10-phenanthroline layer and a WO3 film is investigated. Minimum thicknesses are determined for these layers to allow for simultaneous operation of both sub-OLEDs in the stacked device. Luminance,current density,voltage measurements, angular dependent spectral emission characteristics, and optical device simulations lead to minimum thicknesses of the n-type doped layer and the TMO layer of 5 and 2.5,nm, respectively. Using data on interface energetic determined by ultraviolet photoelectron and inverse photoemission spectroscopy, it is shown that the actual charge generation occurs between the WO3 layer and its neighboring hole-transport material, 4,4',4"-tris(N -carbazolyl)-triphenyl amine. The role of the adjacent n-type doped electron transport layer is only to facilitate electron injection from the TMO into the adjacent sub-OLED. [source] Highly Efficient p-i-n and Tandem Organic Light-Emitting Devices Using an Air-Stable and Low-Temperature-Evaporable Metal Azide as an n-DopantADVANCED FUNCTIONAL MATERIALS, Issue 11 2010Kyoung Soo Yook Abstract Cesium azide (CsN3) is employed as a novel n-dopant because of its air stability and low deposition temperature. CsN3 is easily co-deposited with the electron transporting materials in an organic molecular beam deposition chamber so that it works well as an n-dopant in the electron transport layer because its evaporation temperature is similar to that of common organic materials. The driving voltage of the p-i-n device with the CsN3 -doped n-type layer and a MoO3 -doped p-type layer is greatly reduced, and this device exhibits a very high power efficiency (57,lm W,1). Additionally, an n-doping mechanism study reveals that CsN3 was decomposed into Cs and N2 during the evaporation. The charge injection mechanism was investigated using transient electroluminescence and capacitance,voltage measurements. A very highly efficient tandem organic light-emitting diodes (OLED; 84,cd A,1) is also created using an n,p junction that is composed of the CsN3 -doped n-type organic layer/MoO3 p-type inorganic layer as the interconnecting unit. This work demonstrates that an air-stable and low-temperature-evaporable inorganic n-dopant can very effectively enhance the device performance in p-i-n and tandem OLEDs, as well as simplify the material handling for the vacuum deposition process. [source] Oxygen-Terminated Nanocrystalline Diamond Film as an Efficient Anode in PhotovoltaicsADVANCED FUNCTIONAL MATERIALS, Issue 8 2010Candy Haley Yi Xuan Lim Abstract The potential of using p-doped nanocrystalline diamond as the anode for organic solar cells, because of its outstanding photostability and well-matched energetics with organic dyes, is demonstrated. The interface dipole and open-circuit potential can be tuned by varying the surface termination on diamond. Oxygenated nanocrystalline diamond (O-NCD) exhibits the best photocurrent conversion among all the surface-treated electrodes studied in this work because of its large open-circuit potential. The good energy alignment of the valence band of O-NCD with the HOMO of poly(3-hexylthiophene), as well as its p-doped characteristics, suggest that O-NCD can replace the hole transport layer, such as PEDOT:PSS, needed for efficient performance on indium tin oxide (ITO) electrodes. If the sheet resistance and optical transparency on NCD can be further optimized, chemical-vapor-deposited diamond electrodes may offer a viable alternative to ITO and fluorinated tin oxide (FTO). [source] Solution-Processible Phosphorescent Blue Dendrimers Based on Biphenyl-Dendrons and Fac -tris(phenyltriazolyl)iridium(III) Cores,ADVANCED FUNCTIONAL MATERIALS, Issue 19 2008Shih-Chun Lo Abstract Solution-processible saturated blue phosphorescence is an important goal for organic light-emitting diodes (OLEDs). Fac -tris(5-aryltriazolyl)iridium(III) complexes can emit blue phosphorescence at room temperature. Mono- and doubly dendronized fac -tris(1-methyl-5-phenyl-3- n -propyl-1H -[1,2,4]triazolyl)iridium(III) 1 and fac -tris{1-methyl-5-(4-fluorophenyl)-3- n -propyl-1H -[1,2,4]triazolyl}iridium(III) 4 with first generation biphenyl-based dendrons were prepared. The dendrimers emitted blue light at room temperature and could be solution processed to form thin films. The doubly dendronized 3 had a film photoluminescence quantum yield of 67% and Commission Internationale de l'Eclairage (CIE) coordinates of (0.17, 0.33). OLEDs comprised of a neat film of dendrimer 3 and an electron transport layer achieved a brightness of 142,cd m,2 at 3.8,V with an external quantum efficiency of 7.9%, and CIE coordinates of (0.18, 0.35). Attachment of the fluorine atom to the emissive core had the effect of moving the luminescence to shorter wavelengths but also quenched the luminescence of the mono- and doubly dendronized dendrimers. [source] Organic Thin-Film Photovoltaic Cells Based on Oligothiophenes with Reduced Bandgap,ADVANCED FUNCTIONAL MATERIALS, Issue 15 2007C. Uhrich Abstract The best polymeric solar cells reported so far are based on a so-called bulk heterojunction of a polythiophene as donor and a soluble fullerene derivative as acceptor. However, these cells still suffer from an unsatisfying photovoltage, typically below 0.7,V. Here, we show that we can achieve higher photovoltages using a new terthiophene end-capped with electron withdrawing dicyanovinyl groups (DCV3T) that increase both the ionization energy and even more strongly the electron affinity of the compound. The new material is tested in cells using a photoactive heterojunction to separate the excitons generated in the oligomer and a p-doped wide-gap transport layer. The solar cells show an open circuit voltage of up to 1.04,V and a broad spectral sensitivity band ranging from 420,nm to 650,nm. Solar cells based on such oligothiophenes are promising candidates for stacked organic solar cells tailored to the sun-spectrum. Moreover, we present first examples of a new concept for organic solar cells: By blending DCV3T with fullerene C60, an enhanced generation of triplet excitons on the oligomer can be achieved via a back and forth transfer of excitons (ping-pong-effect). [source] QOS considerations for future military satcom networks with link layer dynamic resource allocationINTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 5 2006Aradhana Narula-Tam Abstract To efficiently utilize limited RF resources, future military packet-switched satellite networks will dynamically allocate resources on the uplink and downlink. Designing the resource allocation algorithms to maximize link layer efficiency is insufficient. The resource allocation algorithms must work cooperatively with the network layer and transport layer to optimize network layer performance and provide quality of service (QoS) to applications and users. Several mechanisms for facilitating this required cooperation between the layers are presented. The individual roles and actions of the layers as well as their interaction are defined. QoS schedulers that continue to provide service differentiation in the presence of link variations are illustrated. Downlink scheduling architectures that provide terminal QoS guarantees are demonstrated. Finally, the interaction between TCP and the dynamic resource allocation algorithms is investigated, leading to suggested modifications of either the resource allocation algorithms, the TCP protocol, or both. Copyright © 2006 John Wiley & Sons, Ltd. [source] Transport protocols in multicast via satelliteINTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 6 2004Gun Akkor Abstract In a wide variety of broadband applications, there is a need to distribute information to a potentially large number of receiver sites that are widely dispersed from each other. Communication satellites are a natural technology option and are extremely well suited for carrying such services because of the inherent broadcast capability of the satellite channel. Despite the potential of satellite multicast, there exists little support for multicast services over satellite networks. Although several multicast protocols have been proposed for use over the Internet, they are not optimized for satellite networks. One of the key multicast components that is affected when satellite networks are involved in the communication is the transport layer. In this paper, we attempt to provide an overview of the design space and the ways in which the network deployment and application requirements affect the solution space for transport layer schemes in a satellite environment. We also highlight some of the issues that are critical in the development of next generation satellite multicast services. Copyright © 2004 John Wiley & Sons, Ltd. [source] Quality of service for satellite IP networks: a surveyINTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 4-5 2003Sastri Kota Abstract The future media rich applications such as media streaming, content delivery distribution and broadband access require a network infrastructure that offers greater bandwidth and service level guarantees. As the demand for new applications increases, ,best effort' service is inadequate and results in lack of user satisfaction. End-to-end quality of service (QoS) requires the functional co-operation of all network layers. To meet future application requirements, satellite is an excellent candidate due to features such as global coverage, bandwidth flexibility, broadcast, multicast and reliability. At each layer, the user performance requirements should be achieved by implementation of efficient bandwidth allocation algorithms and satellite link impairment mitigation techniques. In this paper, a QoS framework for satellite IP networks including requirements, objectives and mechanisms are described. To fully understand end-to-end QoS at each layer, QoS parameters and the current research are surveyed. For example at physical layer (modulation, adaptive coding), link layer (bandwidth allocation), network layer (IntServ/DiffServ, MPLS traffic engineering), transport layer (TCP enhancements, and alternative transport protocols) and security issues are discussed. Some planned system examples, QoS simulations and experimental results are provided. The paper also includes the current status of the standardization of satellite IP by ETSI, ITU and IETF organizations. Copyright © 2003 John Wiley & Sons, Ltd. [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] Smart sunglasses based on electrochromic polymersPOLYMER ENGINEERING & SCIENCE, Issue 11 2008Chao Ma Smart sunglasses based on electrochromic polymers are proposed and developed in this study. This article discusses the design, processing, and the optical and electrical performance of a prototype smart sunglasses based on cathodic electrochromic (EC) polymers, which show several merits compared with traditional materials for sunglasses lens as well as other smart window materials. It is a multilayer design of device. The conjugated polymer, poly[3,3-dimethyl-3,4-dihydro-2H-thieno [3,4-b] [1,4]dioxepine] (PProDOT-Me2), is utilized as the electrochromic working layer. The counter layer of the device is vanadium oxide (V2O5) film, which serves as an ion storage layer. There is also a polymer gel electrolyte acting as the ionic transport layer, sandwiched between the working and counter layers. The characteristics of the prototype device are reported, including transmittance (%T), driving power, response time, open circuit memory, and lifetime. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers [source] | ||||||||||||||||||||||