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Cd M (cd + m)
Selected AbstractsAn 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] High-Performance All-Polymer White-Light-Emitting Diodes Using Polyfluorene Containing Phosphonate Groups as an Efficient Electron-Injection LayerADVANCED FUNCTIONAL MATERIALS, Issue 17 2010Baohua Zhang Abstract We report an efficient non-doped all-polymer polymer white-light-emitting diode (PWLED) with a fluorescent three-color, white single polymer as an emissive layer, an ethanol-soluble phosphonate-functionalized polyfluorene (PF-EP) as an electron-injection/electron-transport layer, and LiF/Al as a cathode, respectively. The all-polymer PWLED achieves a peak external quantum efficiency of 6.7%, a forward viewing luminous efficiency of 15.4 cd A,1 and a power efficiency of 11.4 lm W,1, respectively, at a brightness of 347 cd m,2 with Commission Internationale d'Eclairage coordinates of (0.37, 0.42) and color rendering index of 85, which is the best results among the non-doped PWLEDs. Moreover, this kind of PWLED not only shows excellent color stability, but also achieves high brightness at low voltages. The brightness reaches 1000, 10000, and 46830 cd m,2 at voltages of 4.5, 5.4, and 7.5 V, respectively. The significant enhancement of white-single-polymer-based PWLEDs with PF-EP/LiF/Al to replace for the commonly used Ca/Al cathode is attributed to the more efficient electron injection at PF-EP/LiF/Al interfaces, and the coordinated protecting effect of PF-EP from diffusion of Al atoms into the emissive layer and exciton-quenching near cathode interfaces. The developed highly efficient non-doped all-polymer PWLEDs are well suitable for solution-processing technology and provide a huge potential of low-cost large-area manufacturing for PWLEDs. [source] Charge-Transporting Polymers based on Phenylbenzoimidazole MoietiesADVANCED FUNCTIONAL MATERIALS, Issue 3 2010Marc Debeaux Abstract A series of novel styrene functionalized monomers with phenylbenzo[d]imidazole units and the corresponding homopolymers are prepared. These side-chain polymers show high glass-transition temperatures that even exceed the corresponding value for the common electron-transporting material 1,3,5-tris(1-phenyl-1H -benzo[d]imidazol-2-yl)benzene (TPBI). Similar electronic behavior between the polymers and TPBI is shown. The polymers are used as matrices for phosphorescent dopants. The fabricated devices exhibit current efficiencies up to 38.5,cd A,1 at 100,cd,m,2 and maximum luminances of 7400,cd m,2 at 10,V with a minimum turn-on voltage as low as 2.70,V in single-layer devices with an ITO/PEDOT:PSS anode (ITO,=,indium tin oxide, PEDOT:PSS,=,poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate)) and a CsF/Ca/Ag cathode. [source] Red-Emitting Polyfluorenes Grafted with Quinoline-Based Iridium Complex: "Simple Polymeric Chain, Unexpected High Efficiency"ADVANCED FUNCTIONAL MATERIALS, Issue 1 2010Zhihua Ma Abstract A series of red-light emitting electrophosphorescent polyfluorenes (PFs) with varying content of a quinoline-based iridium complex, (PPQ)2Ir(acac) (bis(2,4-diphenylquinolyl-N,C2,) iridium(acetylacetonate)), in the side chain are synthesized by Suzuki polycondensation. Because of the efficient Förster energy transfer from the PF main chain to (PPQ)2Ir(acac) and direct charge trapping on the complex, the electroluminescent emission from PF is nearly completely quenched, even though the amount of iridium complex incorporated into the polymers is as low as 1,mol %. Based on a single-layer device configuration, a luminous efficiency of up to 5.0,cd A,1 with a luminance of 2000,cd m,2 and Commission Internationale de L'Eclairage coordinates of (0.63, 0.35) (x, y) is realized, which is far superior to that of previously reported red-light emitting PFs containing benzothiazole- and isoquinoline-based iridium complexes. This result is beyond expectations, especially when considering that the simple polymeric chain involved has no additional charge-transporting moieties. Noticeably, the device efficiency remains as high as 4.2,cd A,1 with a luminance of 4000,cd m,2 even at current densities of 100,mA cm,2. Further optimization of the device configuration by incorporating an additional electron-injection layer leads to improved efficiencies of 8.3 and 7.5,cd A,1 at luminances of 100 and 1000,cd m,2, respectively. This state-of-the-art performance indicates that covalently attaching quinoline-based iridium complexes to a PF backbone is a simple and effective strategy to develop high-efficiency red-light emitting electrophosphorescent polymers. [source] Multifunctional Fluorene-Based Oligomers with Novel Spiro-Annulated Triarylamine: Efficient, Stable Deep-Blue Electroluminescence, Good Hole Injection, and Transporting Materials with Very High TgADVANCED FUNCTIONAL MATERIALS, Issue 24 2009Zuoquan Jiang Abstract A series of fluorene-based oligomers with novel spiro-annulated triarylamine structures, namely DFSTPA, TFSTPA, and TFSDTC, are synthesized by a Suzuki cross-coupling reaction. The spiro-configuration molecular structures lead to very high glass transition temperatures (197,253,°C) and weak intermolecular interactions, and consequently the structures retain good morphological stability and high fluorescence quantum efficiencies(0.69,0.98). This molecular design simultaneously solves the spectral stability problems and hole-injection and transport issues for fluorene-based blue-light-emitting materials. Simple double-layer electroluminescence (EL) devices with a configuration of ITO/TFSTPA (device A) or TFSDTC (device B)/ TPBI/LiF/Al, where TFSTPA and TFSDTC serve as hole-transporting blue-light-emitting materials, show a deep-blue emission with a peak around 432,nm, and CIE coordinates of (0.17, 0.12) for TFSTPA and (0.16, 0.07) for TFSDTC, respectively, which are very close to the National Television System Committee (NTSC) standard for blue (0.15, 0.07). The maximum current efficiency/external quantum efficiencies are 1.63,cd A,1/1.6% for device A and 1.91,cd A,1/2.7% for device B, respectively. In addition, a device with the structure ITO/DFSTPA/Alq3/LiF/Al, where DFSTPA acts as both the hole-injection and -transporting material, is shown to achieve a good performance, with a maximum luminance of 14,047,cd m,2, and a maximum current efficiency of 5.56,cd A,1. These values are significantly higher than those of devices based on commonly usedN,N,-di(1-naphthyl)- N,N,-diphenyl-[1,1,-biphenyl]-4,4,-diamine (NPB) as the hole-transporting layer (11,738,cd m,2 and 3.97,cd A,1) under identical device conditions. [source] A Bipolar Host Material Containing Triphenylamine and Diphenylphosphoryl-Substituted Fluorene Units for Highly Efficient Blue ElectrophosphorescenceADVANCED FUNCTIONAL MATERIALS, Issue 17 2009Fang-Ming Hsu Abstract Highly efficient blue electrophosphorescent organic light-emitting diodes incorporating a bipolar host, 2,7-bis(diphenylphosphoryl)-9-[4-(N,N -diphenylamino)phenyl]-9-phenylfluorene (POAPF), doped with a conventional blue triplet emitter, iridium(III) bis[(4,6-difluoro-phenyl)pyridinato- N,C2´]picolinate (FIrpic) are fabricated. The molecular architecture of POAPF features an electron-donating (p-type) triphenylamine group and an electron-accepting (n-type) 2,7-bis(diphenyl-phosphoryl)fluorene segment linked through the sp3 -hybridized C9 position of the fluorene unit. The lack of conjugation between these p- and n-type groups endows POAPF with a triplet energy gap (ET) of 2.75,eV, which is sufficiently high to confine the triplet excitons on the blue-emitting guest. In addition, the built-in bipolar functionality facilitates both electron and hole injection. As a result, a POAPF-based device doped with 7,wt% FIrpic exhibits a very low turn-on voltage (2.5,V) and high electroluminescence efficiencies (20.6% and 36.7,lm W,1). Even at the practical brightnesses of 100 and 1000,cd m,2, the efficiencies remain high (20.2%/33.8,lm W,1 and 18.8%/24.3,lm W,1, respectively), making POAPF a promising material for use in low-power-consumption devices for next-generation flat-panel displays and light sources. [source] Efficient Light-Emitting Devices Based on Phosphorescent Polyhedral Oligomeric Silsesquioxane MaterialsADVANCED FUNCTIONAL MATERIALS, Issue 16 2009Xiaohui Yang Abstract Synthesis, photophysical, and electrochemical characterizations of iridium-complex anchored polyhedral oligomeric silsesquioxane (POSS) macromolecules are reported. Monochromatic organic light-emitting devices based on these phosphorescent POSS materials show peak external quantum efficiencies in the range of 5,9%, which can be driven at a voltage less than 10,V for a luminance of 1000,cd m,2. The white-emitting devices with POSS emitters show an external quantum efficiency of 8%, a power efficiency of 8.1,lm W,1, and Commission International de'lÉclairage coordinates of (0.36, 0.39) at 1000,cd m,2. Encouraging efficiency is achieved in the devices based on hole-transporting and Ir-complex moieties dual-functionalized POSS materials without using host materials, demonstrating that triplet-dye and carrier-transporting moieties functionalized POSS material is a viable approach for the development of solution-processable electrophosphorescent devices. [source] The Design and Realization of Flexible, Long-Lived Light-Emitting Electrochemical CellsADVANCED FUNCTIONAL MATERIALS, Issue 16 2009Junfeng Fang Abstract Polymer light-emitting electrochemical cells (LECs) offer an attractive opportunity for low-cost production of functional devices in flexible and large-area configurations, but the critical drawback in comparison to competing light-emission technologies is a limited operational lifetime. Here, it is demonstrated that it is possible to improve the lifetime by straightforward and motivated means from a typical value of a few hours to more than one month of uninterrupted operation at significant brightness (>100,cd m,2) and relatively high power conversion efficiency (2 lm W,1 for orange-red emission). Specifically, by optimizing the composition of the active material and by employing an appropriate operational protocol, a desired doping structure is designed and detrimental chemical and electrochemical side reactions are identified and minimized. Moreover, the first functional flexible LEC with a similar promising device performance is demonstrated. [source] Exploiting a Dual-Fluorescence Process in Fluorene,Dibenzothiophene- S,S -dioxideCo-Polymers to Give Efficient Single Polymer LEDs with Broadened EmissionADVANCED FUNCTIONAL MATERIALS, Issue 4 2009Simon M. King Abstract A description of the synthesis of random (9,9-dioctylfluorene-2,7-diyl),(dibenzothiophene- S,S -dioxide-3,7-diyl) co-polymers (p(F-S)x) by palladium-catalyzed Suzuki cross-coupling polymerization where the feed ratio of the latter is varied from 2 to 30,mol % (i.e., x,=,2,30) is given. Polymer light emitting devices are fabricated with the configuration indium tin oxide/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid)/p(F,S)x/Ba/Al. The device external quantum efficiency increased as the ratio of the S co-monomer was increased, up to a maximum of 1.3% at 100,mA cm,2 for p(F-S)30 and a brightness of 3 770,cd m,2 (at 10,V). The S units impart improved electron injection, more balanced mobilities, and markedly improved device performance compared to poly(9,9-dioctylfluorene) under similar conditions. These co-polymers display broad emission, observed as greenish-white light, which arises from dual fluorescence, viz. both local excited states and charge transfer states. Utilizing dual emission can reduce problems associated with Förster energy transfer from high-energy to-low energy excited states. [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] Solution-Processible Red Iridium Dendrimers based on Oligocarbazole Host Dendrons: Synthesis, Properties, and their Applications in Organic Light-Emitting Diodes,ADVANCED FUNCTIONAL MATERIALS, Issue 18 2008Junqiao Ding Abstract A series of novel red-emitting iridium dendrimers functionalized with oligocarbazole host dendrons up to the third generation (red-G3) have been synthesized by a convergent method, and their photophysical, electrochemical, and electroluminescent properties have been investigated. In addition to controlling the intermolecular interactions, oligocarbazole-based dendrons could also participate in the electrochemical and charge-transporting process. As a result, highly efficient electrophosphorescent devices can be fabricated by spin-coating from chlorobenzene solution in different device configurations. The maximum external quantum efficiency (EQE) based on the non-doped device configuration increases monotonically with increasing dendron generation. An EQE as high as 6.3% was obtained as for the third generation dendrimer red-G3, which is about 30 times higher than that of the prototype red-G0. Further optimization of the device configuration gave an EQE of 11.8% (13.0,cd A,1, 7.2,lm W,1) at 100,cd m,2 with CIE coordinates of (0.65, 0.35). The state-of-the-art performance indicated the potential of these oligocarbazole-based red iridium dendrimers as solution processible emissive materials for organic light-emitting diode applications. [source] Rational Design of Chelating Phosphine Functionalized Os(II) Emitters and Fabrication of Orange Polymer Light-Emitting Diodes Using Solution Process,ADVANCED FUNCTIONAL MATERIALS, Issue 2 2008M. Cheng Abstract A new series of charge neutral Os(II) pyridyl azolate complexes with either bis(diphenylphosphino)methane (dppm) or cis -1,2-bis(diphenylphosphino)ethene (dppee) chelates were synthesized, and their structural, electrochemical, photophysical properties and thermodynamic relationship were established. For the dppm derivatives 3a and 4a, the pyridyl azolate chromophores adopt an eclipse orientation with both azolate segments aligned trans to each other, and with the pyridyl groups resided the sites that are opposite to the phosphorus atoms. In sharp contrast, the reactions with dppee ligand gave rise to the formation of two structural isomers for all three kind of azole chromophores, with both azolate or neutral heterocycles (i.e., pyridyl or isoquinolinyl fragments) located at the mutual trans -disposition around the Os metal (denoted as series of a and b complexes). These chelating phosphines Os(II) complexes show remarkably high thermal stability, among which and several exhibit nearly unitary phosphorescence yield in deaerated solution at RT. A polymer light-emitting device (PLED) prepared using 0.4 mol % of 5a as dopant in a blend of poly(vinylcarbazole) (PVK) and 30 wt % of 2- tert -butylphenyl-5-biphenyl-1,3,4-oxadiazole (PBD) exhibits yellow emission with brightness of 7208 cd m,2, an external quantum efficiency of 10.4 % and luminous efficiency of 36.1 cd A,1 at current density of 20 mA cm,2. Upon changing to 1.6 mol % of 6a, the result showed even better brightness of 9212 cd m,2, external quantum efficiency of 12.5 % and luminous efficiency of 46.1 cd A,1 at 20 mA cm,2, while the max. external quantum efficiency of both devices reaches as high as 11.7 % and 13.3 %, respectively. The high PL quantum efficiency, non-ionic nature, and short radiative lifetime are believed to be the determining factors for this unprecedented achievement. [source] Phosphorescent Light-Emitting Transistors: Harvesting Triplet ExcitonsADVANCED MATERIALS, Issue 48 2009Ebinazar B. Namdas Phosphorescent light-emitting transistors, in which light emission from singlet and triplet energy levels is harvested using solution-processed materials (see figure), are presented. While a green phosphorescent dendrimer exhibits an external quantum efficiency of 0.45% at 480,cd m,2, a red polymer/phosphorescent small-molecule blend produces a brightness exceeding 30,cd m,2 with a relatively high hole mobility of 2.5,×,10,2,cm2 V,1 s,1. [source] Transparent Inverted Organic Light-Emitting Diodes with a Tungsten Oxide Buffer Layer,ADVANCED MATERIALS, Issue 20 2008Jens Meyer Highly efficient transparent OLEDs are demonstrated. A novel WO3 buffer layer protects the organics during the sputter deposition of the top ITO electrode. L,J,V and SIMS analysis yield optimized devices with a 60,nm thick WO3 layer. Very high efficiencies of 38 cdA,1 and 30 lm W,1 at 100,cd m,2 are obtained. At the same time the transmittance throughout the visible part of the spectrum exceeds 75%. [source] Carbazolevinylene-based polymers and model compounds with oxadiazole and triphenylamine segments: Synthesis, photophysics, and electroluminescenceJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2008Panagiotis D. Vellis Abstract Two new soluble alternating carbazolevinylene-based polymers POXD and PTPA as well as the corresponding model compounds MOXD and MTPA were synthesized by Heck coupling. POXD and MOXD contained 2,5-diphenyloxadiazole segments, while PTPA and MTPA contained triphenylamine segments. All samples displayed high thermal stability. The polymers had higher glass transition temperature (Tg) than their corresponding model compounds. The samples showed absorption maximum at 364,403 nm with optical band gap of 2.62,2.82 eV. They emitted blue-green light with photoluminescence (PL) emission maximum at 450,501 nm and PL quantum yields in THF solution of 0.15,0.36. The absorption and the PL emission maxima of PTPA and MTPA were blue-shifted as compared to those of POXD and MOXD. The electroluminescence (EL) spectra of multilayered devices made using four materials exhibited bluish green emissions, which is well consistent with PL spectra. The EL devices made using poly(vinyl carbazole) doped with MOXD and MTPA as emitting materials showed luminances of 12.1 and 4.8 cd m,2. POXD and PTPA exhibited 25.4, and 96.3 cd m,2, respectively. The polymer containing the corresponding molecules in the repeating group showed much higher device performances. Additionally, POXD and MOXD exhibited better stability of external quantum efficiency (EQE) and luminous efficiency with current density resulting from enhancing the electron transporting properties. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5592,5603, 2008 [source] Synthesis and properties of novel ,,, alternating polymers with triphenylamine and organosilicon unitsAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 12 2001Koichi Sakamaki Abstract We have synthesized novel ,,, conjugated polymers with N,N -bis(p -ethynylphenyl)- N -(p -tolyl)amine as the ,-unit. The electroluminescent devices, with a double-layer system composed of Alq and the present polymers as the emitting-electron-transporting and hole-transporting layers respectively, emit green electroluminescence with a maximum intensity of 760 cd m,2. Copyright © 2001 John Wiley & Sons, Ltd. [source] | ||||||||||