High Luminescence Quantum Efficiency Research Articles

High luminescence quantum efficiency of green mesophase silicate thin film incorporated with rare earth complex

Mesophase silica thin film doped with in-situ formed binary terbium (Tb) complex was synthesized through a simple one-step evaporation-induced self-assembly method. In this process, the precursors of rare earth complex and surfactant were added into hydrolyzed tetramethoxy-silane (TMOS) together and the inorganic/organic mesophase thin film was formed after spin coating. The mesophase structure was characterized as a 2D-hexagonal structure by X-ray diffraction (XRD) analysis. The excitation spectra (λem=544nm) and emission spectra (λex=315nm) indicated that the binary complex, Tb(SA)3, formed in-situ during the formation of the film. Under the UV excitation, the mesophase silica thin film showed bright and consistent green luminescence. The luminescence quantum efficiency of the hybrid thin film was confirmed to be 35.2%.

Improving spectral response of monocrystalline silicon photovoltaic modules using high efficient luminescent down‐shifting Eu3+ complexes

ABSTRACTOne way to improve the spectral response of solar cells in the ultraviolet (UV) region is to convert high energy photons into lower energy ones via luminescent down‐shifting (LDS) technique. Eu3+ complexes are excellent LDS species because of their high luminescence quantum efficiency and large Stokes‐shift. In this paper, we aim to optimize the LDS property of Eu3+ complexes for monocrystalline silicon (c‐Si) photovoltaic (PV) modules by chemical modification of the UV absorbing antenna ligands. Our results show that the LDS performances of Eu3+ complexes are strongly dependent on their absorption and emission properties. By carefully modifying the absorption and emission features, the LDS performances of Eu3+ complexes can be significantly improved. The spectroscopic features of the Eu3+ complex with a bispinene‐containing bipyridyl ligand match well with the requirement of ideal LDS species for the c‐Si PV module. Simple coating of polyvinyl acetate film doped with this complex onto the surface of c‐Si PV module leads to increase of the external quantum efficiency in the UV region and enhancement of the PV module efficiency η (from 16.05% to 16.37%). Copyright © 2012 John Wiley & Sons, Ltd.

Synthesis and Luminescence Properties of Three Europium Complexes with Phenanthroline Derivatives and β-Diketonates

Three novel Eu-complexes based on phenanthroline derivatives as second ligands have been synthesized and characterized by element analysis, 1H NMR, FT-IR, UV-vis, and PL. The luminescence spectra presented characteristic emission lines of Eu3+ ion. The results of luminescence spectra indicated that the Eu3+ ion occupied only a single site, and the ligand filed surrounding the Eu3+ ion was highly polarizable. Meanwhile, all complexes exhibited relative high luminescence quantum efficiency (η). Among these Eu-complexes, the complex Eu (DBM)3HPIP exhibited the lowest quantum efficiency due to the presence of O-H oscillators in this complex, the result indicated different phenanthroline derivatives as second ligands can significantly influence the luminescence properties of Eu-complexes.

Rare earth (Eu 3+, Tb 3+) centered composite gels Si–O–M (M = B, Ti) through hexafluoroacetyl-acetone building block: Sol–gel preparation, characterization and photoluminescence

This report focuses on the syntheses of a series of novel photoactive composite xerogels materials in which the functionalized hexafluoroacetylacetone (HFAASi) organic components are grafted into the different inorganic networks (SiO 2–B 2O 3 or SiO 2–TiO 2) via covalent bonds through a sol–gel process. Subsequently, the physical characterization and especially photoluminescent properties of the resulting xerogel materials are studied in detail. Except for composite xerogels linked to SiO 2–TiO 2 networks, all of these composite xerogels exhibit homogeneous microstructures and morphologies, suggesting that molecular-based materials are obtained with strong covalent bonds between the organic β-diketone ligand and inorganic matrices. In addition, the ternary rare earth composite gels present stronger luminescent intensities, longer lifetimes, and higher luminescent quantum efficiencies than the binary ones, indicating that the introduction of the second ligands (phen) can sensitize the luminescent emission of the rare earth ions in the ternary hybrid systems. It should be especially noted that these composite xerogels based on Si–O–B networks possess not only higher thermal stability but also stronger luminescent intensities than the other systems linked to different inorganic networks.

Ternary rare earth sulfoxide-functionalized mesoporous hybrids Phen-RE (OBDS(BSAB)) 3-SBA-15 (RE = Eu, Tb): Coordination bonding assembly, characterization, and photoluminescence

Novel mesoporous SBA-15 type of hybrid materials (OBDS-SBA-15 and BSAB-SBA-15) are synthesized by co-condensation of tetraethoxysilane (TEOS) and the modified sulfoxide (OBDSSi and BSABSi, OBDS = oxobenzyldimethyl sulphoxide, BSAB = benzylsulfingl acetylbenzene) in the presence of Pluronic P123 surfactant as a template. The preservation of the organic ligand structure during the hydrothermal synthesis and the surfactant extraction process is confirmed by Fourier transform infrared FTIR, TGA and XRD measurements. Novel luminescent organic–inorganic mesoporous hybrids containing RE 3+ (Eu 3+, Tb 3+) complexes and functionalized mesoporous silica matrix SBA-15 (OBDS-SBA-15 and BSAB-SBA-15) have been assembled with chemical bonding, which are designated as Phen-RE(OBDS) 3-SBA-15 and Phen-RE(PPS) 3-SBA-15, are obtained by introducing the RE(NO 3) 3 and 1,10-phenanthroline (Phen) complexes into the hybrid materials via the coordination reaction. The mesostructure of hybrid materials (OBDS-SBA-15 and BSAB-SBA-15) is characterized by TEM, XRD and N 2 adsorption measurements. The luminescence properties of these resulting materials are characterized in details, which reveals that the Phen-RE(OBDS) 3-SBA-15 mesoporous hybrids exhibit stronger luminescent intensities, longer lifetimes and higher luminescent quantum efficiencies than those of Phen-RE(BSAB) 3-SBA-15 hybrids.

Photophysical Properties of Ternary Hybrid System of Lanthanide Center Linking Organically Modified Silica and Polymeric Chain

According to coordination chemistry principle and molecular assembly technology, series of ternary lanthanide centered hybrid systems have been constructed through coordination bonds. Among one component (ligand) is organically modified Si-O network, which originates from the functional molecular bridge (BFPPSi) by the functionalization of 1,3-bis(2-formylphenoxy)-2-propanol (BFPP) with 3-(triethoxysilyl)propyl isocyanate. In the second component (ligand), three different organic polymeric chains are introduced, poly-(methyl methacrylate) (PMMA, from the polymerization of MMA with the benzoyl peroxide [BPO] as the initiator), poly-(methyl acrylic acid) (PMAA, from the polymerization of MAA with the BPO as the initiator), polyvinyl pyridine, respectively. All these ternary hybrid materials show homogeneous, regular microstructure, suggesting the existence of assembly process of lanthanide centers, inorganic Si-O network and organic polymer chain. Compared to the binary hybrids without polymer chain, the photoluminescent properties of these ternary hybrids present stronger luminescent intensities, longer lifetimes and higher luminescent quantum efficiencies indicating that the introduction of organic polymer chain is favorable for the luminescence of the whole hybrid systems.

Blue light-emitting and electron-transporting materials based on dialkyl-functionlized anthracene imidazophenanthrolines

Two novel blue light-emitting materials based on bis( tert-butyl)anthracenyl-imidazophenanthrolines ( BAIPs) have been synthesized and extensively characterized. Both materials exhibited a non-aggregate feature with high fluorescent quantum efficiency and excellent thermal stability. They can serve both as emissive and electron-transporting materials used in electroluminescence (EL) device for blue emission with high luminescence and external quantum efficiency. This study demonstrates that they are potentially useful for a wide range of applications in EL technology.

Synthesis, structural characterization, and photo and electroluminescence of a novel terbium(III) complex: {Tris(acetylacetonate) [1,2,5]thiadiazolo[3,4-f][1,10]phenanthroline}terbium(III)

Lanthanides ion complexes have been intensively investigated as light emitting materials due to their interesting photophysical properties, such as narrow line luminescence with a long lifetime, large Stokes shift and high luminescence quantum efficiency. Here we report the synthesis, structural and photophysical properties of a new Tb(III) complex. This complex showed strong photoemission of green light both in solution and in the solid state as well as the characteristic emission lines of the Tb(III) ion. The electroluminescence properties of the complex were also studied and we obtained bright green light emission through the use of a co-deposited structure. The fabricated device showed a typical diode behavior with a low threshold bias voltage (around 10 V).

Hybrid materials of SBA-16 functionalized by rare earth (Eu 3+, Tb 3+) complexes of modified β-diketone (TTA and DBM): Covalently bonding assembly and photophysical properties

Novel mesoporous SBA-16 type of hybrids TTA-S16 and DBM-S16 were synthesized by co-condensation of modified β-diketone (TTA-Si and DBM-Si, DBM=1,3-diphenyl-1,3- propanepione, TTA=2-thenoyltrifluoroacetone) and tetraethoxysilane (TEOS) in the presence of Pluronic F127 as template, which were confirmed by FTIR, XRD, 29Si CP-MAS NMR, and N 2 adsorption measurements. Novel organic–inorganic mesoporous luminescent hybrid containing RE 3+ (Eu 3+, Tb 3+) complexes covalently attached to the functionalized ordered mesoporous SBA-16 (TTA-S16 and DBM-S16), which were designated as bpy- RE-TTA-S16 and bpy- RE-DBM-S16, were obtained by sol–gel process. The luminescence properties of these resulting materials were characterized in detail, and the results reveal that mesoporous hybrid material bpy-Eu-TTA-S16 present stronger luminescent intensities, longer lifetimes, and higher luminescent quantum efficiencies than the corresponding DBM-containing materials bpy-Eu-DBM-S16, while bpy-Tb-DBM-S16 exhibit the stronger characteristic emission of Tb 3+ and longer lifetime than the corresponding TTA-containing materials bpy-Tb-TTA-S16.

YVO4: RE3+(RE = Eu, Sm, Dy, Er) nanophosphors: Facile hydrothermal synthesis, microstructure, and photoluminescence

YVO4: 10%RE3+(RE = Eu, Sm, Dy, Er) nanophosphors have been synthesized by a facile modified hydrothermal technology to obtain the high purity. The key procedure for this hydrothermal process is the adding order of precursors, in which excess sodium vanadate should be added in the solution of rare earth nitrates. The microstructure (crystal phase, morphology, particle size) of these phosphors are characterized by x-ray powder diffraction, scanning electron microscope, and transmission electron microscope, which indicates that there are some cube-like crystals with tetragonal zircon structure and the average particle size is approximately 40 nm. The luminescent behaviors for the four rare earth ion-activated YVO4nanophosphors have been studied, and, for YVO4: 10%Eu3+nanophosphors in particular, it is found that a different hydrothermal process influences the phase composition, microstructure, and photoluminescence. This result suggests that the hydrothermal synthesis process (by adding sodium vanadate to the solution of rare earth nitrates) is favorable for YVO4nanophosphor to obtain pure phase, small particle size, long luminescent lifetime, and high luminescence quantum efficiency.

Lanthanide (Eu3+, Tb3+)/β-Diketone Modified Mesoporous SBA-15/Organic Polymer Hybrids: Chemically Bonded Construction, Physical Characterization, and Photophysical Properties

Novel organic-inorganic mesoporous luminescent polymeric hybrid materials containing lanthanide (Eu(3+), Tb(3+)) complexes covalently bonded to mesoporous silica SBA-15 have been successfully prepared by co-condensation of the modified 2-thenoyltrifluoroacetone (TTA-Si) and tetraethoxysilane (TEOS) in the presence of Pluronic P123 surfactant as a template. 2Z-Thenoyltrifluoroacetone (TTA) was grafted onto the coupling agent 3-(triethoxysilyl)-propyl isocyanate (TEPIC) and used as the first precursor, and the other precursor PMMA was synthesized through the addition polymerization reaction of the monomer methyl methacrylate. Then these precursors coordinated to rare earth ions, and the final mesoporous polymeric hybrid materials Ln(TTA-SBA-15)(3)PMMA (Ln = Eu, Tb) were obtained after hydrolysis and copolycondensation with the tetraethoxysilane (TEOS) via a sol-gel process. In addition, for comparison, SBA-15 covalently bonded with the binary Ln(3+) complexes with TTA ligand were also synthesized, denoted as Ln(TTA-SBA-15)(3) (Ln = Eu, Tb). All of these hybrid materials have high surface area, uniformity in the mesostructure, and good crystallinity. The detailed luminescence studies on all the materials showed that the ternary rare-earth mesoporous polymeric hybrid materials present stronger luminescent intensities, longer lifetimes, and higher luminescent quantum efficiencies than the binary rare-earth mesoporous hybrid materials, indicating that the introduction of the organic polymer chain is a benefit for the luminescence properties of the overall hybrid system.

Mesoporous hybrids containing Eu 3+ complexes covalently bonded to SBA-15 functionalized: Assembly, characterization and photoluminescence

A novel series of luminescent mesoporous organic–inorganic hybrid materials has been prepared by linking Eu 3+ complexes to the functionalized ordered mesoporous SBA-15 which was synthesis by a co-condensation process of 1,3-diphenyl-1,3-propanepione (DBM) modified by the coupling agent 3-(triethoxysilyl)-propyl isocyanate (TEPIC), tetraethoxysilane (TEOS), Pluronic P123 surfactant as a template. It was demonstrated that the efficient intramolecular energy transfer in the mesoporous material Eu(DBMSi-SBA-15) 3phen mainly occurred between the modified DBM (named as DBM-Si) and the central Eu 3+ ion. So the Eu(DBMSi-SBA-15) 3phen showed characteristic emission of Eu 3+ ion under UV irradiation with higher luminescence quantum efficiency. Moreover, the mesoporous hybrid materials exhibited excellent thermal stability as the lanthanide complex was covalently bonded to the mesoporous matrix.

Covalently bonding assembly and photophysical properties of luminescent molecular hybrids Eu–TTA–Si and Eu–TTASi–MCM-41 by modified thenoyltrifluoroacetone

In the context, the two novel kinds of hybrid materials, TTA–Si directly chemically bonded molecular hybrids and the corresponding MCM-41 host assembling hybrids were prepared. The organic–inorganic mesoporous luminescent materials were synthesized by linking Eu 3+ complexes to the functionalized ordered mesoporous MCM-41 with modified thenoyltrifluoroacetone (TTA–Si) by co-condensation of tetraethoxysilane (TEOS) in the presence of the cetyltrimethylammonium bromide (CTAB) surfactant as template. Thenoyltrifluoroacetone (TTA) was grafted with coupling agent 3-(triethoxysilyl)-propyl isocyanate and the as-derived functional bridge molecule (denoted as TTA–Si) was introduced into inorganic polymeric host MCM-41 through covalent bonds, resulting in the molecular hybrid material. The luminescence properties of these resulting materials were characterized in detail, and the results reveal that they all have high surface area, uniformity in the mesostructure and crystallinity. The efficient intramolecular energy transfer in mesoporous material Eu–TTASi–MCM-41 mainly occurs between the modified ligand TTA–Si and the central Eu 3+ ion. In addition, the constructed covalently bonded hybrids present the longer luminescent lifetimes than common Eu(III) β-diketones complexes for improvement of stability. Especially the mesoporous luminescent material Eu–TTASi–MCM-41possesses high luminescence quantum efficiency .

Lanthanide (Eu3+, Tb3+) Centered Hybrid Materials using Modified Functional Bridge Chemical Bonded with Silica: Molecular Design, Physical Characterization, and Photophysical Properties

1,3-Bis(2-formylphenoxy)-2-propanol (BFPP) was first synthesized and then grafted to 3-(triethoxysilyl)propyl isocyanate (TESPIC) to achieve a molecular precursor BFPP-Si through the hydrogen-transfer nucleophilic addition reaction between the hydroxyl group of BFPP and the isocyanate group of TESPIC. Then, a chemically bonded lanthanide/inorganic/organic hybrid material (BFPP-Si-Ln) was constructed using BFPP-Si as a bridge molecule that can both coordinate to lanthanide ions (Eu3+ or Tb3+) and form an inorganic Si-O network with tetraethoxysilane (TEOS) after cohydrolysis and copolycondensation processes. Furthermore, two types of ternary rare-earth/inorganic/organic hybrids (BFPP-Si-Dipy-Ln and BFPP-Si-Phen-Ln) were assembled by the introduction of the second ligands (4,4'-bipyridyl and 1,10-phenanthroline) into the above system. All of these hybrid materials exhibit homogeneous microstructures and morphologies, suggesting the occurrence of self-assembly of the inorganic network and organic chain. Measurements of the photoluminescent properties of these materials show that the ternary rare-earth/inorganic/organic hybrids present stronger luminescent intensities, longer lifetimes, and higher luminescent quantum efficiencies than the binary hybrids, indicating that the introduction of the second ligands can sensitize the luminescence emission of the lanthanide ions in the ternary hybrid systems.

The synthesis and crystal structures of new 2-aminomethylbenzimidazole Zinc(II) complexes exhibiting luminescence

Two new blue luminescent Zn(II) complexes, [ZnL2(H2O)]Cl2 · H2O (1) and [ZnL2Cl][ZnLCl2] · NO3 (2) (L = 2-aminomethylbenzimidazole) have been synthesized and characterized spectroscopically and crystallographically. The structure of complex (1) can be described as a square pyramid. In the complex (2), there are two units [ZnLCl2] (a), and [ZnL2Cl]+ (b), which have a distorted tetrahedral geometry and a slightly distorted trigonal bipyramidal coordination geometry, respectively. In these complexes, significant multiple inter- and intra-molecular hydrogen bonding and π–π stacking interactions are shown. These contacts lead to aggregation and supramolecular assembly of complexes (1) and (2) into 3D and 2D frameworks, respectively. Fluorescent analysis in the dilute DMF solution and solid state shows that both complexes exhibit intense emission in blue region. They display high blue luminescence quantum efficiency due to a metal-to-ligand charge transfer (MLCT) and have a bathochromic shift of the emission energy compared with the free ligand L. The emission intensity of complex (2) is higher than that of complex (1).

Rare-Earth/Inorganic/Organic Polymeric Hybrid Materials: Molecular Assembly, Regular Microstructure and Photoluminescence

2-Hydroxynicotinic acid (HNA) was grafted by 3-(triethoxysilyl)propyl isocyanate (TEPIC) to achieve the molecular precursor HNA-Si through the hydrogen-transfer nucleophilic addition reaction between the hydroxyl group of HNA and the isocyanate group of TEPIC. Then, a chemically bonded rare-earth/inorganic polymeric hybrid material (A) was constructed using HNA-Si as a bridge molecule that can both coordinate to rare-earth ions (HNA-Si-RE) and form an inorganic Si-O network with tetraethoxysilane (TEOS) after cohydrolysis and copolycondensation processes. Further, three types of novel rare-earth/inorganic/organic polymeric hybrids (B-D) were assembled by the introduction of three different organic polymeric chains into the above system. First, methacrylic acid (MAA) [or methacrylic acid and acrylamide (ALM) in the molar ratio of 1:1] was mixed to polymerize (or copolymerize) with benzoyl peroxide (BPO) as the initiator to form poly(methacrylic acid) (PMAA) [or poly(methacrylic and acrylamide) (PMAALM)], and then PMAA or PMAALM was added to the precursor HNA-Si before the assembly of HNA-Si-RE, resulting in the hybrid materials HNA-Si-RE-PMAA (B) and HNA-Si-RE-PMAALM (C). Second, poly(vinylpyrrolidone) (PVP) was added to coordinate to the rare-earth ions by the carbonyl group in the complex HNA-Si-RE, to achieve the hybrid HNA-Si-RE-PVP (D). All of these hybrid materials exhibit homogeneous, regular, and ordered microstructures and morphologies, suggesting the occurrence of self-assembly of the inorganic network and organic chain. Measurements of the photoluminescent properties of these materials show that the ternary rare-earth/inorganic/organic polymeric hybrids present stronger luminescent intensities, longer lifetimes, and higher luminescent quantum efficiencies than the binary rare-earth/inorganic polymeric hybrids, indicating that the introduction of the organic polymer chain is a benefit for the luminescence of the overall hybrid system.

Design and syntheses of blue luminescent zinc(II) and cadmium(II) complexes with bidentate or tridentate pyridyl-imidazole ligands

A series of luminescent Zn(II) and Cd(II) complexes have been prepared based on three different π-conjugated ligands, 2-(2-pyridyl)-imidazole (HL1), 2-(2-pyridyl)-benzimidazole (HL2) and 2,6-bis(benzimidazol-2yl)-pyridine (H 2L3). The PL spectra of the ligands exhibit a bathochromic shift in agreement with the extended π-conjugation of the ligand. The spectra of the complexes with the ligands follow the same rule. The structures of Zn(L2) 2H 2O ( 5), [Cd(L2) 2(H 2O) 2] · 2DMSO ( 6), Zn(HL3) 2 ( 9) and Cd(HL3) 2 ( 10) have been established by X-ray crystallography. The structure of 5 can be best described as a square pyramid. The coordination geometries of 6, 9 and 10 can be described as distorted octahedrons. In the solid state and in DMSO, these complexes show emission maxima in the blue region. The complexes have a bathochromic shift of the emission energy in sharp contrast to the free ligands. They display blue luminescence and have high luminescence quantum efficiency. A theoretical study reveals that the emissions are assigned to intraligand transitions of the deprotonated L2 and HL3 ligands, and the metal ions in the complexes play a key role in stabilizing the ligand and promoting the luminescence, which is consistent with the experimental results.

Molecular design of luminescent Eu(III) complexes as lanthanide lasing material and their optical properties

Luminescent polymer (PMMA) containing a Eu(III) complex with a fast radiation rate and a high luminescence quantum efficiency (75 ± 5%), (bis-triphenylphosphineoxide)(tris-hexafluoroacetylacetonato)europium(III) (Eu(hfa) 3(TPPO) 2), was fabricated. The quantum yield and the radiation rate of the luminescent polymer were found to be 75 ± 5% and 1.1 × 10 3 s −1, respectively. An Eu(III) complex-doped polymer thin-film was also prepared by use of polyphenylsilsesquioxane (PPSQ) to construct a waveguide lanthanide laser. We propose a strategy for the molecular design of luminescent Eu(III) complexes aiming at lanthanide lasing.

Synthesis and properties of transition metals and rare-earth metals doped ZnS nanoparticles

The synthesis and study of nanostructured materials have become a major interdisciplinary area of research over the past 20 years. Semiconductor nanoparticles play a major role in several new technologies, the intense interest in this area derives from their unique chemical, physical and electronic properties, which give their potential use in the fields of displays, lighting, sensors and lasers, as well as other areas. Transition metal ions or/and rare-earth metal ions doped ZnS nanoparticle is one of the most popular topics of semiconductor phosphors. As the factors of quantum size effect, surface states and the position of impurities in nanosized semiconductor be considered, the process of synthesis is very important for the doped ZnS nanoparticles, therefore, several kinds of methods have been concluded in this literature. There are many interesting phenomena that have been observed, for example, the shift and broadening of spectrum, high luminescent quantum efficiency, shorting of emission lifetime and upconversion emission. Different theoretical models presented by various groups to explain the phenomenon have also been reviewed. This literature review aims to highlight recent advances in the synthesis of doped ZnS semiconductor nanoparticle materials and their wonderful properties.

High luminescence quantum efficiency of Eu3C-doped SnO2–SiO2 glasses due to excitation energy transfer from nano-sized SnO2 crystals

The strong Eu3+ photoluminescence in xSnO2–(100–ܨ)SiO2 derived bythe sol–gel method was reported. It was shown that Eu3+ ions were embedded in SnO2 nanocrystals (tetragonal, rutile) surrounded by a SiO2 glass matrix. Time-resolved photoluminescence spectra and excitation spectra revealed that Eu3+ ions could receive excitation energy from electron–hole pairs in SnO2 semiconductor nanocrystal, whose band-gap energy shifted to the higher energy side due to the quantum size effect,and was tuned to an optimum frequency for energy transfer to Eu3C ions. Absolute quantum luminescence efficiencies were found to be 60.5 (internal) and 26.7% (external).