Improved efficiency by doping blue iridium (III) complex in europium complex-based light-emitting diodes

We demonstrated high-efficiency red organic light-emitting diodes (OLEDs) employing a europium complex, Eu (III) tris( thenoyltrifluoroacetone) 3,4,7,8-tetramethyl-1,10-phenanthroline (Eu(TTA)(3)(Tmphen)), as an emitter and a blue electrophosphorescent complex, Iridium ( III) bis[4,6-di-fluorophenyl-pyridinato-N,C-2] picolinate (FIrpic), as an assistant dopant codoped into 4,4-N, N-dicarbazole-biphenyl (CBP) host as an emissive layer. A pure red electroluminescence (EL) only from Eu3+ ions at 612 nm with a full width at half maximum of 3 nm was observed and the EL efficiency was significantly enhanced. The maximum EL efficiency reached 7.9 cd A(-1) at 0.01 mA cm(-2) current density, which is enhanced by 2.8 times compared with electrophosphorescence-undoped devices. The large improvements are attributed to energy transfer assistance effects of FIrpic, indicating a promising method for obtaining efficient red OLEDs based on rare-earth complexes.

Europium-directed self-assembly of a luminescent supramolecular gel from a tripodal terpyridine-based ligand.

Eu(III), the last piece in the puzzle: Europium-induced self-assembly of ligands having a C(3)-symmetrical benzene-1,3,5-tricarboxamide core results in the formation of luminescent gels. Supramolecular polymers are formed through hydrogen bonding between the ligands. The polymers are then brought together into the gel assembly through the coordination of terpyridine ends by Eu(III) ions (blue dashed arrow: distance between two ligands in the strand direction).

Efficient white organic light-emitting diodes using europium complex as the red unit

Efficient white organic light-emitting diodes (WOLEDs) using europium complex as the red unit are presented. The WOLEDs were fabricated by using the structure of indium tin oxide (ITO)/N, N'-di(naphthalene-1-yl)-N, N'-diphenyl-benzidine (NPB)/4,4-N, N-dicarbazolebiphenyl (CBP) : bis(2,4-diphenylquinolyl-N, C-2) iridium (acetylacetonate) ((PPQ)(2)Ir(acac)) : Eu (III) tris(thenoyltrifluoroacetone) 3,4,7,8-tetramethyl-1,10-phenanthroline (Eu(TTA)(3)(Tmphen))/NPB/2-methyl-9,10-di(2-naphthyl)anthracene (MADN) : p-bis (p-N, N-di-phenyl-aminostyryl)benzene (DSA-Ph)/9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP)/tris(8-hydroxyquinoline) aluminium (Alq3)/LiF/Al.

Novel Near-Infrared Luminescent Hybrid Materials Covalently Linking with Lanthanide [Nd(III), Er(III), Yb(III), and Sm(III)] Complexes via a Primary beta-Diketone Ligand: Synthesis and Photophysical Studies

A series of novel, colorless, and transparent sot-gel derived hybrid materials Ln-DBM-Si covalently grafted with Ln(DBM-OH)(3)center dot 2H(2)O (where DBM-OH = o-hydroxydibenzoylmethane, Ln = Nd, Er, Yb, and Sin) were prepared through the primary beta-diketone ligand DBM-OH. The structures and optical properties of Ln-DBM-Si were studied in detail. The investigation results revealed that the lanthanide complexes were successfully in situ grafted into the corresponding hybrids Ln-DBM-Si. Upon excitation at the maximum absorption of ligands, the resultant materials displayed excellent near-infrared luminescence.

Syntheses, structures and near-IR luminescent studies on ternary lanthanide (Er-III, Ho-III, Yb-III, Nd-III) complexes containing 4,4,5,5,6,6,6-heptafluoro-1-(2-thienyl)hexane-1,3-dionate

The ligand Hhfth [4,4,5,5,6,6,6-heptafluoro-1-(2-thienyl)hexane-1,3-dione], which contains a heptafluoropropyl group, has been used to synthesize several new ternary lanthanide complexes (Ln = Er, Ho, Yb, Nd) in which the synergistic ligand is 1,10-phenanthroline (phen) or 2,2'-bipyridine (bipy). The two series of complexes are [Ln(hfth)(3)phen] [abbreviated as (Ln)1, where Ln = Er, Ho, Yb] and [Ln(hfth)(3)bipy] [abbreviated as (Ln)2, where Ln = Er, Ho, Yb, Nd]. Members of the two series have been structurally characterized. The growth morphology, diffuse reflectance (DR) spectra, thermogravimetric analyses, and photophysical studies of these complexes are described in detail. After ligand-mediated excitation of the complexes, they all show the characteristic near-infrared (NIR) luminescence of the corresponding Ln(3+) ions (Ln = Er, Ho, Yb, Nd). This is attributed to efficient energy transfer from the ligands to the central Ln(3+) ions, i.e. an antenna effect. The heptafluorinated substituent in the main hfth sensitizer serves to reduce the degree of vibrational quenching. With these NIR-luminescent lanthanide complexes, the luminescent spectral region from 1300 to 1600 nm, which is of particular interest for telecommunication applications, can be covered completely.

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.

Luminescent properties of Langmuir-Blodgett films of europium bisphthalocyanine

Eu(III)-octa-4-(tetrahydrofurfuroxy) phthalocyanine (EuPc2') was synthesied and characterized by elementary analysis, IR, MS, UV-vis spectra. EuPc2' has good film-forming ability from determination of isotherm of pi-A. The complex LB film was formed by depositing of EuPc2' on a quartz slide with the LB techniques of the Z-type, The luminescent properties of pure and doped LS films were determined. The results showed that pure films have good luminescent properties, the thicker the LB films, the stronger the fluorescent intensity. The films doped with o-phenanthroline (abbreviated as phen) made the relative intensity of fluorescent emission behavior enhance in comparison to that of pure LB film, But the amount of phen may be not too much. Our results showed that EuPc2':phen = 1: 10 (molar ratio) has the best fluorescent behavior. The electronic spectroscopic characterization of the LB films is also given.

The phase transitions of hetero atoms substituted molecular sieves Me-VPI-5(Me=Mg, Ti, Sn, Si) and their influence on spectra structures of Eu(III) ion

The hetero atom substituted aluminophosphate molecular sieves Me-VPI-5(Me = Mgt Ti, Sn, Si) were synthesized hydrothermally. Rare earth ions are originally doped into these microporous materials by aqueous solution ion exchange procedures. The phase transitions of the microporous materials are investigated by high-temperature and high-pressure experimental techniques. The influence of the phase transitions on the rare earth ions' spectral structures is discussed, With the increase of temperature, Eu(II)Mg-VPI-5 is converted into Eu(II)Mg-AIPO(4)-8, then into tridymite phase. The pressure has a notable influence on Eu(II) ion's spectral structures. The spectral structures have changed regularly with the increase of pressure.

Study of the luminescence of tris(2-thenoyltrifluoroacetonato)lanthanide(III) complexes covalently linked to 1,10-phenanthroline-functionalized hybrid sol-gel glasses

The solubility and uniform distribution of lanthanide complexes in sol-get glasses can be improved by covalently linking the complexes to the sol-gel matrix. In this study, several lanthanide beta-diketonate complexes (Ln = Nd, Sm, Eu, Tb, Er, Yb) were immobilized on a 1,10-phenanthroline functionalized sol-gel glass. For the europium(Ill) complex, a sol-gel material of diethoxydimethylsilane (DEDMS) with polymer-like properties was derived. For the other lanthanide complexes, the sol-gel glass was prepared by using a matrix of tetramethoxysilane (TMOS) and DEDMS. Both systems were prepared under neutral reaction conditions. High-resolution emission and excitation spectra were recorded. The luminescence lifetimes were measured. (c) 2004 Elsevier B.V. All rights reserved.

Persistent luminescence of SrAl2O4:Ce(III), Dy, Eu nanotubes, nanowires and core-shells for people with disabilities: nano-emergency

Este estudo transversal está focado na propriedade de luminescência persistente do aluminato de estrôncio co-dopado com cério (III), disprósio (III) e európio (II), SrAl2O4:Ce3+, Dy3+, Eu2+, em sistemas de sinalização de áreas de risco e emergências para pessoas com deficiências. Na área da ciência e engenharia dos materiais, foram desenvolvidos novos materiais com características nanométricas, nanotubos, nanoarames e nanobastões luminescentes de SrAl2O4:Ce3+, Dy3+, Eu2+ para aplicações na área da reabilitação e acessibilidade de pessoas com deficiências. Os nanotubos foram obtidos a partir de micro- e nano-partículas precursoras sintetizadas por reacção do estado-sólido e tratamento térmico de recozedura (1273-1473 K). Os nanoarames e nanobastões foram preparados por moagem, sonificação e recozedura (373 K). Novas nanocápsulas de aluminatos luminescentes dopados com cério (III) e encapsulados com TiO2 foram criadas de modo a obter-se materiais multifuncionais, designadamente com acção fotocatalítica antimicrobiana, antibacteriana e resistência à água. Tais aluminatos podem ser amplamente aplicados como superfícies higiénicas, auto-limpantes, em biomateriais, no domínio de medicamentos antibióticos, na formulação de vacinas, e com ênfase à aplicação em cerâmicas fotoluminescentes. As metodologias de obtenção de tais nanoestruturas de aluminato de estrôncio dopado com cério (III) e do seu encapsulamento, desenvolvidas no âmbito desta tese, são aplicáveis a diversos aluminatos dopados com outros iões lantanídeos (Ln consiste em La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Tm ou Lu) com a fórmula M(1-x-y)N2O4:Cex, Lny, onde M é Be, Mg, Ca, Sr ou Ba. Na área da oftalmologia, foi desenvolvido um equipamento médico para o diagnóstico de biofuncionalidade das células retinais fotoreceptoras, e como suporte à telemedicina oftalmológica. Este equipamento foi utilizado para realizar testes de visão cromática FM100HUE em fundo branco/preto para a personalização de materiais luminescentes. Os resultados demonstraram uma biofuncionalidade celular à visibilidade fotópica das cores em fundo preto superior no grupo de tratamento, composto por pessoas com retinopatia diabética (n=38), em comparação ao grupo de referência (n=38). Estes resultados sugerem a recomendação de materiais com fotoluminescência persistente (λem=485-555 nm), incluindo SrAl2O4:Ce3+, Dy3+, Eu2+, para o referido grupo de tratamento, em sinalização de emergência e em ambientes de baixa iluminação. Na área da arquitectura, foi proposta uma nova aplicação dos referidos nanomateriais luminescentes à base de SrAl2O4:Ce3+, Dy3+, Eu2+ em cerâmica de revestimento, tendo em vista a sua boa visibilidade e uso por pessoas com deficiências. Novos pavimentos, cerâmicos, fotoluminescentes, foram desenhados com propriedades multisensoriais (contraste táctil, sonoro e visual) e antimicrobianas, para pessoas portadoras de deficiências utilizarem, no escuro, com a prioridade de salvar vidas em emergências. Tais pisos, com relevos, podem ser combinados de modo a compor um sistema exclusivo de sinalização fotoluminescente multisensorial que possibilita a rápida evacuação mediante o uso de auxílios de mobilidade (e.g. bengala, cadeira de rodas, andadores, muletas). A solução integrada de tais inovações que potencializa a propriedade de luminescência persistente de SrAl2O4:Ce3+, Dy3+, Eu2+ de modo acessível para as pessoas com deficiências, pode contribuir para salvar vidas, no escuro, em emergências.

Caracterização e modificação de heteroestruturas de nitretos do grupo III

Os nitretos binários semicondutores do grupo III, e respetivos compostos, são vastamente estudados devido à sua possível aplicabilidade em dispositivos optoeletrónicos, tais como díodos emissores de luz (LEDs) e LASERs, assim como dispositivos para a eletrónica de elevadas temperatura, potência e frequência. Enquanto se concretizou a comercialização na última década de LEDs e LASERs recorrendo ao ternário In1-yGayN, estudos das propriedades fundamentais estruturais e óticas, assim como de técnicas de processamento no desenvolvimento de novas aplicações de outros ternários do grupo III-N encontram-se na sua fase inicial. Esta tese apresenta a investigação experimental de filmes finos epitaxiais de Al1-xInxN crescidos sobre camadas tampão de GaN e de Al1-yGayN e o estudo do recozimento e implantação de super-redes (SL) compostas por pontos quânticos de GaN (QD) envolvidos por camadas de AlN. Apesar do hiato energético do Al1-xInxN poder variar entre os 0,7 eV e os 6,2 eV e, por isso, numa gama, consideravelmente superior à dos ternários Al1-yGayN e InyGa1-yN, o primeiro é o menos estudado devido a dificuldades no crescimento de filmes com elevada qualidade cristalina. É efetuada, nesta tese, uma caracterização estrutural e composicional de filmes finos de Al1-xInxN crescidos sobre camadas tampão de GaN e de Al1-yGayN usando técnicas de raios-X, feixe de iões e de microscopia. Mostra-se que o Al1-xInxN pode ser crescido com elevada qualidade cristalina quando a epitaxia do crescimento se aproxima da condição de rede combinada do Al1-xInxN e da camada tampão (GaN ou Al1-yGayN), isto é, com conteúdo de InN de ~18%, quando crescido sobre uma camada de GaN. Quando o conteúdo de InN é inferior/superior à condição de rede combinada, fenómenos de relaxação de tensão e deterioração do cristal tais como o aumento da rugosidade de superfície prejudicam a qualidade cristalina do filme de Al1-xInxN. Observou-se que a qualidade dos filmes de Al1-xInxN depende fortemente da qualidade cristalina da camada tampão e, em particular, da sua morfologia e densidade de deslocações. Verificou-se que, dentro da exatidão experimental, os parâmetros de rede do ternário seguem a lei empírica de Vegard, ou seja, variam linearmente com o conteúdo de InN. Contudo, em algumas amostras, a composição determinada via espetrometria de retrodispersão de Rutherford e difração e raios-X mostra valores discrepantes. Esta discrepância pode ser atribuída a defeitos ou impurezas capazes de alterar os parâmetros de rede do ternário. No que diz respeito às SL dos QD e camadas de AlN, estudos de recozimento mostraram elevada estabilidade térmica dos QD de GaN quando estes se encontram inseridos numa matriz de AlN. Por implantação iónica, incorporou-se európio nestas estruturas e, promoveu-se a ativação ótica dos iões de Eu3+ através de tratamentos térmicos. Foram investigados os efeitos da intermistura e da relaxação da tensão ocorridos durante o recozimento e implantação nas propriedades estruturais e óticas. Verificou-se que para fluências elevadas os defeitos gerados por implantação são de difícil remoção. Contudo, a implantação com baixa fluência de Eu, seguida de tratamento térmico, promove uma elevada eficiência e estabilidade térmica da emissão vermelha do ião lantanídeo incorporado nos QD de GaN. Estes resultados são, particularmente relevantes, pois, na região espetral indicada, a eficiência quântica dos LEDs convencionais de InGaN é baixa.

Spectroscopic investigation of the interactions between emeraldine base polyaniline and Eu(III) ions

The interactions of emeraldine base form of polyaniline (EB-PANI) and Eu(III) ions in 1-methyl-2-pyrrolidinone (NMP) solution and in films have been investigated by UV-vis-NIR, resonance Raman. luminescence and electron paramagnetic resonance (EPR) spectroscopies. These spectroscopic techniques allowed to characterize quinone and semiquinone segments in the polymeric chains. and the oxidation state of europium ions in Eu-PANI samples. For high values of Eu(III)/N molar ratio (24/1) the presence of a weak polaronic absorption band at 980 nm in UV-vis-NIR spectrum and the observation of bands at 1330 and 1378 (nu(center dot)(C-N+)) cm(-1) due to emeraldine salt in the Raman spectrum at 1064 nm indicate a low doping degree. Oxidation of EB-PANI to pernigraniline base (PB-PANI) occurs in diluted solutions. The experimental data showed that the solvent plays an important role on the nature of formed species. The narrow EPR signal at g = 2.006 (line width 8G) confirms the presence of PANI radical cations in Eu-PANI film. The absence of broad signal characteristic of Eu(II) in EPR spectrum suggested that europium ions are primarily at Eu(III) oxidation state. The luminescence spectra of Eu-PANI film presented emission bands at 405 and 418 nm assigned to PANI moieties and bands at 594,615 and 701 nm assigned to (5)D(0) -> (7)F(J) (J = 1, 2 and 4, respectively) transitions of Eu(III). EPR and photoluminescence data confirm that europium ions are mainly in Eu(III) oxidation state in Eu(III)/PANI films. (C) 2008 Elsevier B.V. All rights reserved.

Evaluation of intramolecular energy transfer process in the lanthanide(III) bis- and tris-(TTA) complexes: Photoluminescent and triboluminescent behavior

This work reports the energy transfer mechanism process of [Eu(TTA)(2)(NO(3))(TPPO)(2)] (bis-TTA complex) and [Eu(TTA)(3)(TPPO)(2)] (tris-TTA complex) based on experimental and theoretical spectroscopic properties, where TTA = 2-thienoyltrifluoroacetone and TPPO = triphenylphosphine oxide. These complexes were synthesized and characterized by elemental analyses, infrared spectroscopy and thermogavimetric analysis. The theoretical complexes geometry data by using Sparkle model for the calculation of lanthanide complexes (SMLC) is in agreement with the crystalline structure determined by single-crystal X-ray diffraction analysis. The emission spectra for [Gd(TTA)(3)(TPPO)(2)] and [Gd(TTA)(2) (NO(3))(TPPO)(2)] complexes are associated to T -> S(0) transitions centered on coordinated TTA ligands. Experimental luminescent properties of the bis-TTA complex have been quantified through emission intensity parameters Omega(lambda)(lambda = 2 and 4), spontaneous emission rates (A(rad)), luminescence lifetime (tau), emission quantum efficiency (eta) and emission quantum yield (q), which were compared with those for tris-TTA complex. The experimental data showed that the intensity parameter value for bis-TTA complex is twice smaller than the one for tris-TTA complex, indicating the less polarizable chemical environment in the system containing nitrate ion. A good agreement between the theoretical and experimental quantum yields for both Eu(Ill) complexes was obtained. The triboluminescence (TL) of the [Eu(TTA)(2)(NO(3))(TPPO)(2)] complexes are discussed in terms of ligand-to-metal energy transfer. (c) 2007 Elsevier B.V. All fights reserved.

Synthesis and structural characterization of Eu(III)-doped Zn7Sb2O12

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)