Efficient red organic light-emitting devices based on a europium complex

An efficient organic light-emitting device using a trivalent europium (Eu) complex Eu(Tmphen)(TTA)(3) (TTA=thenoyltrifluoroacetone, Tmphen=3,4,7,8-tetramethyl-1,10-phenanthroline) as the dopant emitter was fabricated. The devices were a multilayer structure of indium tin oxide/N,N-diphenyl-N,N-bis(3-methylphenyl)-1,1-biphenyl-4,4-diamine (40 nm)/ Eu complex:4,4-N,N-dicarbazole-biphenyl (1%, 30 nm)/2,9-dimethyl,4,7-diphenyl-1,10phenanthroline (20 nm)/AlQ (30 nm)/LiF (1 nm)/Al (100 nm). A pure red light with a peak of 612 nm and a half bandwidth of 3 nm, which is the characteristic emission of trivalent europium ion, was observed. The devices show the maximum luminance up to 800 cd/m(2), an external quantum efficiency of 4.3%, current efficiency of 4.7 cd/A, and power efficiency of 1.6 lm/W. At the brightness of 100 cd/m(2), the quantum efficiency reaches 2.2% (2.3 cd/A).

A dinuclear aluminum 8-hydroxyquinoline complex with high electron mobility for organic light-emitting diodes

A dinuclear aluminum 8-hydroxyquinoline complex (DAlq(3)) with improved electron mobility was designed for organic light-emitting diodes. The electron mobility in DAlq(3) was determined via transient electroluminescence (EL) from bilayer devices with structure of indium tin oxide (ITO)/N,N-'-di(naphthalene-1-yl)-N,N-'-diphenyl-benzidine (NPB)/DAlq(3)/Mg:Ag. It was found that the electron mobility in DAlq(3) is between 3.7-8.4x10(-6) cm(2)/Vs at electric fields ranging between 1.2x10(6) and 4.0x10(6) V/cm, which is a factor of two higher than that in Alq(3). The DAlq(3) also shows a higher EL efficiency of 2.2 cd/A (1.2 Lm/W), as compared to Alq(3) with an EL efficiency of 2.0 cd/A (1.0 Lm/W), which is attributed to more balanced electron and hole recombination due to the improved electron mobility of DAlq(3).

Nitrate-citrate combustion synthesis and properties of Ce1-xSmxO2-x/2 solid solutions

A nitrate-citrate combustion route to synthesize nanocrystalline samarium-doped ceria powders for solid electrolyte ceramics is presented. This route is based on the gelling of nitrate solutions by the addition of citric acid and ammonium hydroxide, followed by an intense combustion process due to an exothermic redox reaction between nitrate and citrate ions. The influence of ignition temperature on the characteristics of the powders was studied. The change of the crystal structure with the content of doped Sm was investigated. High temperature X-ray, and Raman scattering were used to characterize the sample. The lattice constant and unit volume increase with doping level and increasing temperature. Dense ceramic samples prepared by uniaxial pressing and sintering in air were also studied.

Synergistic extraction of zinc(II) by mixtures of primary amine N1923 and Cyanex272

The extraction of zinc(II) and cadmium(II) from chloride solution by mixtures of primary amine N1923 and Cyanex272 (HA) was studied. The synergistic effect was observed for the extraction of zinc(II) while no synergistic effect for cadmium(II), which makes it possible to separate zine(II) and cadmium(II) with the mixtures. The results showed that zinc(II) was extracted as (RNH3Cl)(3) . ZnCIA instead of ZnA(2) . 2HA which was extracted by Cyanex272 alone. The extraction mechanism was discussed and the formation constants and thermodynamic functions were determined. The separation factors between zinc(II) and cadmium(II) were calculated.

Synthesis of 2-benzylthio-5-phenyl-3,4-disubstituted thiophenes by intramolecular condensation of alpha-oxo ketene dibenzylthioacetals

A facile route to 2-benzylthio-5-phenyl-3,4-disubstituted thiophenes was described. Catalyzed by sodium hydroxide, the title compounds were synthesized in moderate to good yields simply from the intramolecular aldol type condensation of alpha-oxo ketene dibenzylthioacetals. The chemical selectivity for this annulation reaction was studied and discussed.

Green electroluminescent device with a terbium beta-diketonate complex as emissive center

In this study, a terbium complex, Tb(acac)(3)bath (acac: acetylacetone, bath: 4,7-diphenyl-1,10-phenanthroline), was synthesized and its luminescent properties were investigated compared with the reported terbium complex, Tb(acac)(3)phen (phen: phenanthroline). When it was used as an emitting material in organic electroluminescent (EL) device, the triple-layer-type device with a structure of glass substrate/ITO (indium-tin oxide)/TPD (N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine)/Tb(acac)(3)bath/Alq(3) (tris (8-hydroxyquinolinato) aluminum)/Al (aluminum) exhibited bright characteristic emission of terbium ion upon applying DC voltage. An apparent difference was observed between the photoluminescence spectrum and the EL spectrum. The EL device exhibited some characteristics of diode and the maximum luminance of 77 cd/m(2) was obtained at 17 V.

Study of methanol adsorption on mica, graphite and ITO glass by using tapping mode atomic force microscopy

Tapping mode atomic force microscopy (AFM) was applied to study the adsorption behavior of methanol on mica, highly oriented pyrolytic graphite (HOPG) and indium-tin oxide (ITO) coated glass substrates. On mica and HOPG substrates surfaces, the thin films of methanol with bilayer and multilayer were observed, respectively. The formation of irregular islands of methanol was also found on HOPG surface. On ITO surface only aggregates and clusters of methanol molecules were formed. The influence of sample preparation on the adsorption was discussed.

A novel terbium (III) beta-diketonate complex as thin film for optical device application

A novel terbium complex, Tb(acac)(3)AAP (acac: acetylacetone, AAP: 4-amino-antipyrine), was synthesized and its luminescent properties were studied. When it was used as an emitting center, triple-layer-type device with a structure of glass substrate/ITO (indium-tin oxide)/TPD (N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine)./Tb(acac)(3)AAP/PBD (2-(4-biphenyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole) or Alq(3) (tris(8-hydroxyquinolinato) aluminum)/Al (aluminum) exhibited bright characteristic emission of terbium ion upon applying d.c. voltage. The maximum luminance of the device is 56 cd/m(2) at 19 V and the maximum luminance efficiency is 0.357 lm/W.

Synthesis of novel nitrogen- and sulfur-containing conjugated polymers used as hole-transporting materials for organic light-emitting diodes

Two series of highly soluble novel nitrogen- and sulfur-containing conjugated polymers were synthesized via an acid-induced self-polycondensation of functional monomers with methyl sulfinyl and aromatic groups. The well-defined structures of synthesized polymers were confirmed by their NMR and IR spectra. The highest occupied molecular orbital energy values for these materials, estimated by cyclic voltammetry, showed a broad range of values from about 5.0 to 5.2 eV used as hole-transport layers (HTL) in two-layer light-emitting diodes ITO/HTL/Alq(3)/Mg:Ag [ITO = indium tin oxide, and Alq(3) = tris(8-quinolinato) aluminum]. The typical turn-on voltage of these diodes was about 4-5 V. The maximum brightness of the device was about 3440 cd/m(2) at 20 V. The maximum efficiency was estimated to be 0.15 1m/W at 10 V.

A novel way to enhance electroluminescence performance based on soluble binary and ternary europium 1,1,1-trifluoroacetylacetonate

Five rare earth complexes (Gd(acae)(3), Gd(TFacaC)(3), Eu(acaC)(3), Eu(TFacaC)(3) and Eu(TFacaC)(3)bipy; acac, acetylacetone; TFacac, 1,1,1-trifluoroacetylacetone; bipy, 2,2'-bipyridyl) were synthesized. By comparing the phosphorescence spectra of Gd(acac)(3) and Gd(TFacac)(3) the effect of the replacement of hydrogen by fluorine was examined. Organic light-emitting devices (OLEDs) based on the corresponding europium complexes as emissive layers were also fabricated by the spin-coating method. The triple-layer-type device with the structure glass substrate/ITO (indium-tin oxide)/PVK [poly(N-vinylcarbazole)]/(PVKEu)-Eu-.(TFacac)(3)bipy:PBD[2-(4-bibipyyl)-5-(4-t-butylbipyl-1,3,4-oxadiazole)]/PBD/Al (aluminum) exhibits a brighter red luminescence than those devices with Eu(acac)(3) and Eu(TFacac)(3) complexes as emissive centers upon applying a d.c. voltage.

Red electroluminescent device with europium 1,1,1-trifluoroacetylacetonate complex as emissive center

By comparing the phosphorescence spectra of Gd(acac)(3) (acac: acetylacetone) and Gd(TFacac)(3) (TFacac: 1, 1, 1-trifluoro-acetylacetone), the effect of fluorine replacing of hydrogen was discussed. It can lower the triplet state energy of acac and make it more suitable to the D-5(1) energy state of europium. Organic electroluminescent (OEL) devices with corresponding europium complexes as emissive layers were fabricated. A triple laver-type device with a structure of glass substrate/indium-tin oxide (ITO)/poly(N-vinylcarbazole) (PVK)/PVK:Eu(TFacac)(3)phen:2-(4-biphenyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole (PBD)/PBD/Al exhibits bright red luminescence upon applying dc voltage, The device has the properties of a diode and the current-bias voltage line was obtained.

Preparation and characterization of PSt-b-PHEMA metal hybrids

The block copolymer polystyrene-b-poly[2-(trimethylsilyloxy)ethylene methacrylate] (PSt-b-PTMSEMA) was synthesized using atom-transfer radical polymerization (ATRP). The hydrolysis of PSt-b-PTMSEMA led to the formation of an amphiphilic block copolymer, polystyrene-b-poly(2-hydroxylethyl methacrylate) (PSt-b-PHEMA), which was characterized by GPC and H-1-NMR. TEM showed that the PSt-b-PHEMA formed a micelle, which is PSt as the core and PHEMA as the shell. Under appropriate conditions, the nickel or cobalt ion cause chemical reactions in these micelles and could be reduced easily. ESCA analysis showed that before reduction the metal existed as a hydroxide; after reduction, the metal existed as an oxide, and the metal content of these materials on the surface is more than that on the surface of the copolymer metal ion. XRD analysis showed that the metal existed as a hydroxide before reduction and existed as a metal after reduction.

Determination of ultra-trace rare-earth elements in human plasma by inductively coupled plasma mass spectrometry

Inductively coupled plasma mass spectrometry (ICP-MS),a highly sensitive inorgnic analytic technique,fits to determine ultra-nace rare-earth elements in human plasma. Under the optimized conditions detection limits for 15 rare-earth elements are in the range of 0.7 (for Eu)-5.4 (for Gd) ng.L-1. Indium as an internal standard element is used to compensate for matrix suppression effect and sensitivity drift. Three kinds of preparation methods, diluted with 1% HNO3, digested with HNO3-H2O2 and with HNO3-HClO4, are checked and compared,and the former is the simplest way to be measured. The samples diluted with 1% HNO3, stored in 4 degrees C, are very steady for 16 days. With the method, 11 healthy plasma samples in Changchun area of China are analysed.

1.54 mu m infrared photoluminescence and electroluminescence from an erbium organic compound

Infrared emission at 1.54 mu m excited optically and electrically from an erbium organic compound tris(acetylacetonato)(1,10-phenanthroline) erbium [Er(acac)(3)(phen)] is observed. The rare-earth complex is dispersed into a polymer matrix of poly(N-vinylcarbazole) (PVK) to fabricate an electroluminescent (EL) device with an ITO/PVK:Er(acac)(3)(phen)/Al:Li/Ag structure, where ITO represents indium-tin-oxide-coated glass. The device shows infrared EL emission at 1.54 mu m, which suggests a simple and cheap method to obtain a light source for 1.54-mu m-wavelength devices in optical communications. (C) 2000 American Institute of Physics. [S0021-8979(00)00301-7].

A comparative study on the electroluminescence properties of some terbium beta-diketonate complexes

By comparing the phosphorescence spectra of Gd(acac)(3) (acac=acetylacetone), Gd(TFacac)3 (TFacac=1,1,1-trifluoroacetylacetone), the effects of fluorine replacement of hydrogen on the triplet state energy of the ligands were revealed. Fluorine can lower the triplet state energy of Hacac and make it more suitable for energy transfer towards the D-5(4) state of terbium. Organic electroluminescent devices (OELDs) with the corresponding trivalent terbium complexes as emissive layers were fabricated. Triple-layer-type devices with a structure of glass substrate/ITO (indium tin oxide)/PVK [poly(N-vinylcarbazole)]/PVK : Tb complex: PBD [2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole]/PBD/Al exhibit bright green luminescence upon applying a dc voltage. The luminance of a device with Tb(TFacac)(3)phen (1,10-phenanthroline) and Tb( TFacac) 3 as emissive layer is higher than that of the corresponding devices with Tb(acac)(3)(phen) and Tb(acac)(3) as emissive layers. The EL device with Tb(TFacac)(3)(phen) as emitter exhibits characteristic emission of Tb3+ ions with a maximum luminance of 58 cd m(-2) at 25 V.