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Transporting Layer (transporting + layer)
Selected AbstractsHighly Efficient Polymer White-Light-Emitting Diodes Based on Lithium Salts Doped Electron Transporting Layer,ADVANCED MATERIALS, Issue 3 2009Fei Huang A Li2CO3 -doped water/alcohol-soluble neutral conjugated polymer is used as the electron-injection layer in a solution-processed polymer OWLED with very high efficiency. A maximum forward viewing luminous efficiency of 36.1 cd A,1 and a power efficiency of 23.4 lm W,1 were achieved, values comparable to those reported for the state-of-the-art vacuum deposited small -molecule OWLEDs. [source] Multifunctional Triphenylamine/Oxadiazole Hybrid as Host and Exciton-Blocking Material: High Efficiency Green Phosphorescent OLEDs Using Easily Available and Common MaterialsADVANCED FUNCTIONAL MATERIALS, Issue 17 2010Youtian Tao Abstract A new triphenylamine/oxadiazole hybrid, namely m -TPA- o -OXD, formed by connecting the meta -position of a phenyl ring in triphenylamine with the ortho -position of 2,5-biphenyl-1,3,4-oxadiazole, is designed and synthesized. The new bipolar compound is applicable in the phosphorescent organic light-emitting diodes (PHOLEDs) as both host and exciton-blocking material. By using the new material and the optimization of the device structures, very high efficiency green and yellow electrophosphorescence are achieved. For example, by introducing 1,3,5-tris(N -phenylbenzimidazol-2-yl)benzene (TPBI) to replace 2, 9-dimethyl-4,7-diphenyl-1, 10-phenanthroline (BCP)/tris(8-hydroxyquinoline)aluminium (Alq3) as hole blocking/electron transporting layer, followed by tuning the thicknesses of hole-transport 1, 4-bis[(1-naphthylphenyl)amino]biphenyl (NPB) layer to manipulate the charge balance, a maximum external quantum efficiency (,EQE,max) of 23.0% and a maximum power efficiency (,p,max) of 94.3 lm W,1 are attained for (ppy)2Ir(acac) based green electrophosphorescence. Subsequently, by inserting a thin layer of m -TPA- o -OXD as self triplet exciton block layer between hole-transport and emissive layer to confine triplet excitons, a ,EQE,max of 23.7% and ,p,max of 105 lm W,1 are achieved. This is the highest efficiency ever reported for (ppy)2Ir(acac) based green PHOLEDs. Furthermore, the new host m -TPA- o -OXD is also applicable for other phosphorescent emitters, such as green-emissive Ir(ppy)3 and yellow-emissive (fbi)2Ir(acac). A yellow electrophosphorescent device with ,EQE,max of 20.6%, ,c,max of 62.1 cd A,1, and ,p,max of 61.7 lm W,1, is fabricated. To the author's knowledge, this is also the highest efficiency ever reported for yellow PHOLEDs. [source] Light emission from different ZnO junctions and nanostructuresPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2009M. Willander Abstract We will discuss our experimental results for optical spectra produced by hole-injection from different p-type organic and inorganic materials into n-type ZnO nanowires. The influence of different growth techniques and conditions on the nanowires and their emission spectral characteristics will then be analyzed and discussed. The latest findings on the mixture of the green emission band responsible for visible light emission from ZnO and the blue light emission from the organic polymer will be presented. Different high brightness light emitting diodes (HB-LEDs) from our grown ZnO nanowires are demonstrated. The p-type multi layer organic structures contain PEDOT:PSS as hole injectors combined with a hole transporting layer, and in some structures, a final top electron blocking/hole barrier stepping layer is placed. The purpose of this layer is to adjust the hole and electron emission from the corresponding junction side to optimize the LED performance. Structural scanning electron microscopy (SEM), electrical (I ,V characteristics), photoluminescence (PL) and electroluminescence (EL) characteristics of these devices are displayed. Theoretically, we study the superfluidity of a two-dimensional system of excitonic polaritons in an optical microcavity with an embedded quantum well. Using the effective low-energy action for thermodynamic phase fluctuations, we obtain an expression for the analogue of the superfluid density in the system in terms of the "current,current" correlation function. The Kosterlits,Thouless transition temperature to the superfluid state as a function of the controlling parameters is calculated. Two methods are considered for producing traps for a polariton system in an optical microcavity. The behaviour of a two-component Bose condensate of photons and excitons is analyzed theoretically for both types of the trap. The Bose condensate is described by the coupled system of equations of the Gross,Pitaevskii type. The approximate wave functions and the spatial profiles of coupled photon and exciton condensates are obtained. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] An Alternative Approach to Constructing Solution Processable Multifunctional Materials: Their Structure, Properties, and Application in High-Performance Organic Light-Emitting DiodesADVANCED FUNCTIONAL MATERIALS, Issue 18 2010Shanghui Ye Abstract A new series of full hydrocarbons, namely 4,4,-(9,9,-(1,3-phenylene)bis(9H -fluorene-9,9-diyl))bis(N,N -diphenylaniline) (DTPAFB), N,N,-(4,4,-(9,9,-(1,3-phenylene)bis(9H -fluorene-9,9-diyl))bis(4,1-phenylene))bis(N -phenylnaphthalen-1-amine) (DNPAFB), 1,3-bis(9-(4-(9H -carbazol-9-yl)phenyl)-9H -fluoren-9-yl)benzene, and 1,3-bis(9-(4-(3,6-di- tert -butyl-9H -carbazol-9-yl)phenyl)-9H -fluoren-9-yl)benzene, featuring a highly twisted tetrahedral conformation, are designed and synthesized. Organic light-emitting diodes (OLEDs) comprising DNPAFB and DTPAFB as hole transporting layers and tris(quinolin-8-yloxy)aluminum as an emitter are made either by vacuum deposition or by solution processing, and show much higher maximum efficiencies than the commonly used N,N,-di(naphthalen-1-yl)- N,N,-diphenylbiphenyl-4,4,-diamine device (3.6 cd A,1) of 7.0 cd A,1 and 6.9 cd A,1, respectively. In addition, the solution processed blue phosphorescent OLEDs employing the synthesized materials as hosts and iridium (III) bis[(4,6-di-fluorophenyl)-pyridinato-N, C2] picolinate (FIrpic) phosphor as an emitter present exciting results. For example, the DTPAFB device exhibits a brightness of 47 902 cd m,2, a maximum luminescent efficiency of 24.3 cd A,1, and a power efficiency of 13.0 lm W,1. These results show that the devices are among the best solution processable blue phosphorescent OLEDs based on small molecules. Moreover, a new approach to constructing solution processable small molecules is proposed based on rigid and bulky fluorene and carbazole moieties combined in a highly twisted configuration, resulting in excellent solubility as well as chemical miscibility, without the need to introduce any solubilizing group such as an alkyl or alkoxy chain. [source] | ||||||||||