Enhanced electroluminescent efficiency from spin-coated europium(III) organic light-emitting device (original) (raw)
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Improved efficiency of organic light-emitting diodes based on a europium complex by fluorescent dye
Journal of Luminescence, 2007
Improved efficiency of organic light-emitting diodes (OLEDs) based on europium complexes have been realized by using a fluorescent dye 4-(dicyanomethylene)-2-t-butyl-6 (1,1,7,7-tetramethyljulolidyl-9-enyl))-4H-pyran (DCJTB) doping .The luminous efficiency of the devices with a fluorescent dye in the emissive layer was found to improve two times of that in devices without fluorescent dye. The devices showed pure red light, which is the characteristic emission of trivalent europium ion with a full-width at half-maximum of 3 nm.The maximum brightness and luminous efficiency reached 1200 cd/m 2 at 23 V and 7.3 cd/A (2.0 lm/w), respectively, at a current density of 0.35 mA/cm 2 .
Synthetic metals, 2002
With two second ligands, 2-(2-pyridyl)benzimidazole (HPBM) and 1-ethyl-2-(2-pyridyl)benzimidazole (EPBM), two novel europium complexes, Eu(TTA) 3 HPBM and Eu(TTA) 3 EPBM (TTA, thenoyltrifluoroacetonato) were synthesized and applied to organic electroluminescent (EL) devices as the emitting materials. The devices of ITO/TPD/Eu(TTA) 3 HPBM (or Eu(TTA) 3 EPBM)/AlQ/Al were fabricated. The EL devices emit red light originating from these two europium complexes. The EL brightness of Eu(TTA) 3 EPBM is much higher than that of Eu(TTA) 3 HPBM. For Eu(TTA) 3 EPBM, a maximum luminance of 36.6 cd/m 2 was achieved at 21 V.
Journal of Non-Crystalline Solids, 2008
This work shows a comparative study of organic light emitting diodes based on four different europium complexes with the general formula, Eu(CLs) 3 bipyridine, where the central ligands are DBM [tris(dibenzoylmethane)], TTA [tris(1-(2-thieneyl)-4,4,4-trifluoro-1,3butanedione)], NTA [tris(1-(2-naphthoyl)-3,3,3-trifluoroacetone)] and BTA [tris(1-(2-benzoyl)-3,3,3-trifluoroacetone)]. All devices have a driving voltage of 14-16 V, a very low electrical current at normal operation (less than 1 mA) and a good Wall Plug Efficiency (up to near 10 À3 %). The most suitable central ligand was found to be DBM, with an optical power up to 200 nW (at 612 nm). The BTA exhibits the lowest stability under high applied voltages. The other central ligands have similar results among them. The electroluminescence spectra clearly show the europium ion transitions (with a strong 5 D 0 ? 7 F 2 line) with a CIE color coordinate around (0.56, 0.34).
The photoluminescent and electroluminescent properties of a new Europium complex
Journal of Luminescence, 2007
A new rare earth (RE) complex Eu(BSA) 3 phen was synthesized. A narrow emission band from a device structure of ITO/PVK: RE complex/LiF/Al was observed, in which poly N-vinylcarbazole (PVK) was used to improve the film-forming and hole-transporting property of the Eu(BSA) 3 phen. Excitation, photoluminescence (PL) and electroluminescence (EL) characteristics of the device were studied and an energy transfer from PVK to europium complex was proposed. Effects of doping ratios of Eu(BSA) 3 phen on the device performance were also studied. r
Tetrahedron, 2013
Two novel bipolar-transporting dinuclear europium(III) complexes incorporating both hole-transporting triphenylamine (TPA) and electron-transporting oxadiazole (OXD) units into the dual phenanthroline ligands were successfully synthesized and characterized by IR, elemental analysis, electrochemical, photophysical analysis, and thermogravimetric analysis, in which the OXD unit was attached onto TPA unit by conjugated and unconjugated linkages for the europium complex A and B, respectively. Compared with complex B, complex A exhibited higher thermal stability and quantum efficiency. A maximum brightness of 296.3 cd/m 2 at voltage of 8.5 V was obtained in the complex A-doped devices with saturated red emission using a blend of poly(vinylcarbazole) and 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole as a host matrix, which is about two-times higher than that from the complex B-doped devices with the same configuration. To best of our knowledge, this is one of the best results based on the dinuclear europium(III) complexes by spin-casting method.
Molecules
This paper reports the synthesis, structure, photophysical, and optoelectronic properties of five eight-coordinate Europium(III) ternary complexes, namely, [Eu(hth)3(L)2], bearing 4,4,5,5,6,6,6-heptafluoro-1-(2-thienyl)-1,3-hexanedione (hth) as a sensitizer and L = H2O (1), dpso (diphenyl sulphoxide, 2), dpsoCH3 (4,4′-dimethyl diphenyl sulfoxide, 3), dpsoCl (bis(4-chlorophenyl)sulphoxide, 4), and tppo (triphenylphosphine oxide, 5) as co-ligands. The NMR and the crystal structure analysis confirmed the eight-coordinate structures of the complexes in solution and in a solid state. Upon UV-excitation on the absorption band of the β-diketonate ligand hth, all complexes showed the characteristic bright red luminescence of the Europium ion. The tppo derivative (5) displayed the highest quantum yield (up to 66%). As a result, an organic light-emitting device, OLED, was fabricated with a multi-layered structure—ITO/MoO3/mCP/SF3PO:[complex 5] (10%)/TPBi:[complex 5] (10%)/TmPyPB/LiF/Al—using ...
We report the design and synthesis of volatile europium β-diketonate Eu(dmh) 3 phen organic hybrid complex by precipitation technique. A series of complexes were synthesized for different pH values, ranging between 8.0 and 6.0 maintaining stoichiometric ratio. Among all the synthesized complexes, Eu(dmh) 3 phen with pH 7 exhibits red intense emission at 613 nm with a sharp spectral bandwidth of 5 nm when excited at a wavelength of 372nm,infering that the synthesized complex is pH sensitive. This complex is further assessed for structural, thermal and luminescence behavior in various solvents. X-ray diffractogram reveals its crystalline nature and FTIR confirms the complete formation of the complex revealing the presence of TTA and bipy structure in the metal complex. TGA/DTA exhibits good thermal stability, which is highly essential for fabricating organic light emitting diodes (OLEDs) for solid state lighting. Hypsochromic shift was observed in the optical absorption spectra of Eu(dmh) 3 phen, when the solvent is changed from basic to acidic media.
Electrophosphorescence emission in organic light-emitting diodes based on (Sm+Eu) complexes
Thin Solid Films, 2004
In this work, we reported the preparation and the characterization of triple-layer electroluminescent organic devices using different blends of the samarium and europium h-diketonate complexes [Sm x Eu y (TTA) 3 (TPPO) 2 ] (x=0.7, 0.9; y=0.3, 0.1) as emitting layer. The organic light-emitting diode (OLED) devices contained 1-(3-methylphenyl)-1,2,3,4-tetrahydroquinoline-6-carboxyaldehyde-1,1V-diphenylhydrazone (MTCD) as hole-transporting layer and tris(8-hydroxyquinoline) aluminum (Alq 3 ) as electron transporting layer. The electroluminescence (EL) spectra present emission narrow bands characteristic of the Sm 3+ and Eu 3+ ions overlapped with a broad band attributed to the molecular electrophosphorescence (EP) from the triplet-singlet (T 1 YS 0 ) transition from the TTA ligand. The intensity ratio of the peaks is determined by the bias voltage applied to the OLED and this fact, together with the ligand electrophosphorescence, allows fabrication of a voltagetunable color light source. D