Blue Fluorescent Materials Research Articles

Three rare Ln–Na heterometallic 3D polymers based on sulfate anion: Syntheses, structures, and luminescence properties

Three Ln–Na heterometallic 3D polymers based on sulfate anion, [LnNa(SO4)2(H2O)] (Ln=Gd (1); Tb (2); Dy (3)), were synthesized under hydrothermal conditions, which are the first examples of Ln–Na sulfates. These compounds crystallize in the trigonal P3121 space group, and display a 6-connected sma topological structure with a Schäfli symbol of (410·65). The characteristic analyses reveal that compounds 1–3 display excellent thermal stability, and all exhibit antiferromagnetic interactions between the metal centers. The luminescent properties of 2 and 3 show the characteristic terbium and dysprosium luminescence. The strong luminescence in the green light (5D4→7F5) region for 2 and blue light (4F9/2→6H15/2) region for 3 indicate that they may be excellent candidates for green or blue fluorescent materials.

Crystallization behaviors and luminescent properties of a new type luminescent material based on poly(butylene succinate) (PBS) prepared via a solution blend

In this paper, films of poly(butylene succinate) (PBS)/poly(N-vinylcarbazole) (PVK) composites were fabricated via a solvent casting method using chloroform as a co-solvent. Effect of PVK phase on the crystallization behaviors and luminescent properties of PVK matrix was investigated by differential scanning calorimetry, X-ray diffraction and fluorescence spectrophotometer. It was found that the PVK phase influenced on the crystallization behaviors of the PBS matrix, e.g. the degree of crystallinity (χc) and the crystallization rate of PBS/PVK composites decreased with increasing the PVK content. And the PVK phase had no obvious effect on the crystal structure of the PBS matrix, while the average grain size of the PBS decreased with the increment of the PVK content. Moreover, the PBS matrix affected the energy absorption and transfer processes of the carbazole groups of the PVK. And the luminescent intensity of PBS/PVK composites gradually improved with the increase of the PVK content. In PBS/PVK composites, when the weight content of the PVK is 41.2 % i.e. PBS/PVK-0.7, the composite possesses fine luminescent properties for potential usage as blue fluorescent biodegradable film materials.

청색 형광과 적색 인광 물질을 사용한 백색 OLED의 발광 특성

We studied white organic light-emitting diodes using blue fluorescent and red phosphorescent materials. White single OLEDs were fabricated using SH-1 : BD-2 (3 vol.%) and CBP : (2 vol.%) as emitting layer (EML). The white single OLED using SH-1 : BD-2 (3 vol.% 8 nm) / CBP : (2 vol.% 22 nm) as emitting layer showed maximum current efficiency of 8.8 cd/A, Commission Internationale de l'Eclairage (CIE) coordinates of (0.403, 0.351) at , and variation of CIE coordinates with (, ) from 500 to . The white tandem OLED using SH-1 : BD-2 (3 vol.% 12 nm) / CBP : (2 vol.% 18 nm) showed maximum efficiency of 19.6 cd/A, CIE coordinates of (0.354, 0.365) at , and variation of CIE coordinates with (, ) from 500 to . Maximum current efficiency of the white tandem OLED was more twice as high as the single OLED. Our findings suggest that tandem OLED was possible to produce improved efficiency and excellent color stability.

Synthesis and electroluminescent properties of blue fluorescent materials based on 9,9-diethyl-N,N-diphenyl-9 H-fluoren-2-amine substituted anthracene derivatives for organic light-emitting diodes

Four 9,9-diethyl-N,N-diphenyl-9H-fluoren-2-amine substituted anthracene derivatives have been designed and synthesized by Suzuki cross coupling reactions. To explore the electroluminescent properties of these blue materials, multilayer blue organic light-emitting diodes were fabricated in the following device structure: indium tin oxide (180nm)/N,N’-diphenyl-N,N’-(1-napthyl)-(1,1′-phenyl)-4,4′-diamine (50nm)/blue emitting materials (1–4) (30nm)/bathophenanthroline (30nm)/lithium quinolate (2nm)/Al (100nm). All devices appeared excellent deep-blue emissions. Among them, a device exhibited a maximum luminance of 5686cd/m2, the luminous, power and external quantum efficiencies of 5.11cd/A, 3.79lm/W, and 4.06% with the Commission International de L'Eclairage coordinates of (0.15, 0.15) at 500cd/m2, respectively.

Efficient Deep Blue Electroluminescence with an External Quantum Efficiency of 6.8% and CIEy < 0.08 Based on a Phenanthroimidazole–Sulfone Hybrid Donor–Acceptor Molecule

Tremendous efforts have been devoted to develop efficient deep blue organic light-emitting diodes (OLEDs) materials with CIEy < 0.10 (Commission International de L’Eclairage (CIE)) and match the National Television System Committee (NTSC) standard blue CIE (x, y) coordinates of (0.14, 0.08) for display applications. However, deep blue fluorescent materials with an external quantum efficiency (EQE) over 5% are still rare. Herein, we report a phenanthroimidazole–sulfone hybrid donor–acceptor (D–A) molecule with efficient deep blue emission. D–A structure molecular design has been proven to be an effective strategy to obtain high electroluminescence (EL) efficiency. In general, charge transfer (CT) exciton formed between donor and acceptor is a weak coulomb bonded hole–electron pair and is favorable for the spin flip that can turn triplet excitons into singlet ones. However, the photoluminescence quantum yield (PLQY) of CT exciton is usually very low. On the other hand, a locally excited (LE) state normally ...

Fluoranthene-Based Molecules as Electron Transport and Blue Fluorescent Materials for Organic Light-Emitting Diodes

Herein we report the synthesis, characterization, and potential application of his (4- (7,9,10-triphenylfluoranthen-8-yl)pheny)sulfone (TPFDPSO2) and 2,8-bis (7,9,10-triphenylfluoranthen-8-yl) dibenzo b, d]-thiophene 5,5-dioxide (TPFDBTO2) as electron transport as well as light-emitting materials. These fluoranthene derivatives were synthesized by oxidation of their corresponding parent sulfide compounds, which were prepared via Diels-Alder reaction. These materials exhibit deep blue fluorescence emission in both solution and thin film, high photoluminescence quantum yield (PLQY), thermal and electrochemical stability over a wide potential range. Hole- and electron-only devices were fabricated to study the charge transport characteristics, and predominant electron transport property comparable with that of a well-known electron transport material, Alq(3), was observed. Furthermore, bilayer electroluminescent devices were fabricated utilizing these fluoranthene derivatives as electron transport as well as emitting layer, and device performance was compared with that of their parent sulfide molecules. The electroluminescence (EL) devices fabricated with these molecules displayed bright sky blue color emission and 5-fold improvement in external quantum efficiency (EQE) with respect to their parent compounds.

Effect of fluorocarbon (trifluoromethyl groups) substitution on blue electroluminescent properties of 9,9′-bianthracene derivatives with twisted intramolecular charge-transfer excited states

By introducing a highly fluorescent 9,9′-bianthracene, fluorocarbon (trifluoromethyl groups) with the different linkage mode on the periphery of the 9,9′-bianthracene core, two novel blue-emissive materials (BAn-(3)-CF3 and BAn-(4)-CF3) were synthesized and characterized. The high luminescence efficiency and excellent stability rendered both promising materials in electroluminescent devices. The twisted intramolecular charge transfer state was demonstrated to enhance the occurrence of singlet excitons in the fluorescent emitter, which was based on the 9,9′-bianthracene moiety. Specifically, the meta-linkage BAn-(3)-CF3 device doped with sky blue fluorescent material 4,4-bis[4-(di-p-tolylamino)styryl]biphenyl showed that the singlet generation fraction was more than 25%, and presented an impressive luminous current efficiency of 5.88 cd A−1 and an external quantum efficiency of 3.15% with a high luminance of over 12,000 cd m−2. Noticeably, the para-linkage BAn-(4)-CF3 device exhibited an excellent efficiency stability with almost unchanged roll-off on the current and power efficiencies, even when the brightness approached 12,000 cd m−2.

A three-dimensional CdII coordination polymer constructed from 1,1'-biphenyl-2,2',5,5'-tetracarboxylate and 1,4-bis(1H-imidazol-1-yl)benzene ligands.

The title coordination polymer, poly[[aqua(μ5-1,1'-biphenyl-2,2',5,5'-tetracarboxylato)bis[μ2-1,4-bis(1H-imidazol-1-yl)benzene]dicadmium(II)] dihydrate], {[Cd2(C16H6O8)(C12H10N4)2(H2O)]·2H2O}n, was crystallized from a mixture of 1,1'-biphenyl-2,2',5,5'-tetracarboxylic acid (H4bpta), 1,4-bis(1H-imidazol-1-yl)benzene (1,4-bib) and cadmium nitrate in water-dimethylformamide. The crystal structure consists of two crystallographically independent Cd(II) cations, with one of the Cd(II) cations possessing a slightly distorted pentagonal bipyramidal geometry. The second Cd(II) centre is coordinated by carboxylate O atoms and imidazole N atoms from two separate 1,4-bib ligands, displaying a distorted octahedral CdN2O4 geometry. The completely deprotonated bpta(4-) ligand, exhibiting a new coordination mode, bridges five Cd(II) cations to form one-dimensional chains via μ3-η(1):η(2):η(1):η(2) and μ2-η(1):η(1):η(0):η(0) modes, and these are further linked by 1,4-bib ligands to form a three-dimensional framework with a (4(2).6(4))(4.6(2))(4(3).6(5).7(2)) topology. The structure of the coordination polymer is reinforced by intermolecular hydrogen bonding between carboxylate O atoms, aqua ligands and crystallization water molecules. The solid-state photoluminescence properties were investigated and the complex might be a candidate for a thermally stable and solvent-resistant blue fluorescent material.

Blue electroluminescent materials based on phenylanthracene-substituted fluorene derivatives for organic light-emitting diodes

Two phenylanthracene-substituted fluorene derivatives, 10-(9,9′-dimethyl-2-(10-phenylanthracen-9-yl)-9H-fluoren-7-yl)-phenylanthracene (1) and 2′,7′-di-(10-phenylanthracen-9-yl)-9,9′-spirobi[9H-fluorene] (2) have been designed, synthesized, and characterized. A device using compound 1 as an emitting material exhibited luminous efficiency, power efficiency, external quantum efficiency and CIE coordinates of 3.37cd/A, 1.50lm/W, 1.87% at 20mA/cm2 and (0.18, 0.25) at 7V, respectively. Furthermore, by exploiting this efficient blue fluorescent material as a blue emitting material with the combination of red phosphorescent bis(2-phenylquinoline)acetylacetonate [(pq)2Ir(acac)], an efficient white OLED (WOLED) with a external quantum efficiency of 1.70%, luminous efficiency of 1.38cd/A, power efficiency of 0.94lm/W at 20mA/cm2 and the color coordinates of (0.33, 0.36) at 14V is demonstrated.

Blue fluorescent materials based on bis(10-phenylanthracen-9-yl) derivatives containing heterocyclic moiety

We synthesized a series of bis(10-phenylanthracen-9-yl) derivatives containing various heterocyclic moieties such as 9-ethylcarbazole, dibenzofuran and dibenzothiophene (1–3) by Suzuki cross-coupling reactions. To explore electroluminescent properties of these materials, multilayered devices were fabricated with configuration of indium–tin–oxide (ITO) (180nm)/4,4′-bis(N-(1-naphthyl)-N-phenylamino)biphenyl (NPB) (50nm)/Emitters 1–3 (30nm)/Tris(8-hydroxyquinolinato) aluminium (Alq3) (15nm)/lithium quinolate (Liq) (2.0nm)/Al (100nm). In particular, a device using 2,8-bis(10-phenylanthracen-9-yl)dibenzo[b,d]furan (2), as an emitter, exhibited efficient blue emission with maximum luminance, luminous, power and external quantum efficiency of 620cd/m2, 2.05cd/A, 1.05lm/W, 1.43% at 20mA/cm2, and CIE coordinates of (x=0.18, y=0.17) at 8V, respectively.

A bistriphenylamine-substituted spirobifluorene derivative exhibiting excellent nonlinearity/transparency/thermal stability trade-off and strong two-photon induced blue fluorescence

A spirobifluorene-bridged donor/donor chromophore, 2,7-bis-(4-(N,N-diphenylamino)phen-1-yl)-9,9′-spirobifluorene (SPF-TP), was found to combine excellent transparency in the near UV–visible region (λcut-off ≤ 420 nm), large two-photon absorption cross-section (4.5 × 103GM) and high thermal stability (Td = 501 °C). In comparison to the reported two-photon absorption molecules, SPF-TP represents the best thermal stability so far described in the literature. The main electronic factors explaining the high two-photon absorption activities of SPF-TP were analyzed by theoretical calculations. Cyclic voltammograms were employed to explore the causes of the excellent transparency of SPF-TP. It was found that the spiroconjugation effect is responsible for the excellent nonlinearity/transparency/thermal stability trade-off in SPF-TP. In addition, SPF-TP is also a good two-photon induced blue fluorescent material with high fluorescence quantum yield (Φ = 0.90, in THF).

Blue Aggregation‐Induced Emission Luminogens: High External Quantum Efficiencies Up to 3.99% in LED Device, and Restriction of the Conjugation Length through Rational Molecular Design

Great efforts have been devoted to seek novel approaches for constructing blue fluorescent materials, which is one of the most important prerequisites for the commercialization of OLEDs. In recent years, various outstanding luminogens with aggregation‐induced emission characteristic exhibit promising applications as emitters, but blue AIE fluorophores with excellent EL performance are still very scarce. Here, five hole‐dominated blue AIE molecules are demonstrated by adopting construction approaches of changing linkage modes and increasing intramolecular torsion together, with the aim to restrict conjugation lengths without sacrificing good EL data. Device results show that the novel synthesized materials could be applied as bifunctional materials, namely blue light‐emitting and hole‐transporting materials, with comparable EL efficiencies, and the ηC,max and ηext,max are up to 8.03 cd A−1 and 3.99% respectively, which is among the best EL performance for blue AIE luminogens.

Synthesis and optoelectronic properties of thieno[2,3-b]thiophene based bis 1,3,4-oxadiazole derivatives as blue fluorescent material for use in organic light emitting diodes

We report the synthesis and optoelectronic properties of a series of symmetrical disubstituted derivatives containing bis 1,3,4-oxadiazole with thieno[2,3-b]thiophene backbone (3a–f). These novel compounds were synthesized by employing simple and convenient synthetic protocol using thieno[2,3-b]thiphene-2,5,dicarboxylic acid as a starting material. The structures of these target molecules were established by their analytical and spectral data. The photo physical and electrochemical studies revealed that these compounds exhibit good blue fluorescent properties with better quantum yield. These compounds are expected to be of use in various optoelectronic applications.

Undoped Blue Organic Light-Emitting Diodes Using 2-Diphenylaminofluoren-7-Ylstyryl Derivatives

Blue fluorescent materials based on diphenylaminofluorenylstyryl derivatives connected with the various end-capping aromatic groups were synthesized and characterized. An OLED, using (E)-9,9-diethyl-7-(4-(4-fluoronaphthalen-1-yl)styryl)-N,N-diphenyl-9 H-fluoren-2-amine(5) in emitting layer, was fabricated. This device showed the highly efficient blue emission with the maximum luminance of 5138 cd/m2, the luminous efficiency of 3.92 cd/A, the power efficiency of 3.17 lm/W, the external quantum efficiency of 2.90% at 20 mA/cm2 and CIE x, y coordinates of (0.14, 0.17).

Blue fluorescent OLED materials and their application for high-performance devices

The authors applied two technologies to improve the efficiency of fluorescent blue organic light-emitting diodes (OLEDs). First, an efficiency-enhancement layer (EEL) was introduced to boost triplet–triplet fusion (TTF). Second, new blue dopants with a higher orientation factor in the emitting layer were developed. Consequently, the external quantum efficiency (EQE) was increased up to 11.5% with Commission Internationale de l’Eclairage (CIE) 1931 color coordinates of (0.138, 0.092). The reported results may lead to EQEs that exceed 14% with fluorescent blue emitters.

Highly efficient green and red phosphorescent OLEDs using novel bipolar blue fluorescent materials as hosts

We investigated highly efficient green and red phosphorescent organic light-emitting diodes (OLEDs) based on two kinds of iridium complexes as the guests and two novel 1,3,5-triazine derivatives as the host materials, respectively. For comparison, the devices using a common fluorescent host 4,4′-N,N′-dicarbazolebiphenyl (CBP) have also been fabricated. Results show that all devices using 1,3,5-triazine derivatives as host have better performance than that of CBP. This may be attributed to the adoption of the hosts, which have suitable HOMO/LUMO levels enabling excitons to form on host and hence favoring efficient energy-transfer from host to guest. In addition, the high bipolar carrier mobility of the host is found to be critical to this kind of doping system, which would balance the injection of both carriers and improve efficiency.

Solution‐processed high‐performance orange phosphorescent and white PLEDs with a high color‐rendering index from an unprecedented π‐stacked and π‐conjugated host material

ABSTRACTA blue fluorescent polymer based on poly(vinyl carbazole) (PVK) and terfluorene, combined to make a chemical hybrid at the carbazole unit (PVK‐TF), is fully characterized in this study. PVK‐TF shows useful emission features, such as peaks at 400, 420, 437, 460, and 496 nm, depending on the processing conditions. It possesses a relatively high triplet energy level (2.23 eV), electrochemical stability, good film‐forming ability, and morphological stability. Based on this blue fluorescent material, highly efficient orange phosphorescent polymer light‐emitting diodes (PLEDs) were fabricated with a maximum efficiency of 21.99 cd A−1, and a maximum luminance of 19552.3 cd m−2. Single‐layer hybrid white PLEDs were developed, with a high color rendering index of 81.9 that emitted across the whole visible spectrum from 380 to 780 nm, corresponding to the Commission International de L'Eclairage coordinates x, y values of around (0.38, 0.40) and CCT = 3774, with a maximum current efficiency of 10.69 cd A−1, and a maximum brightness of 15723.3 cd m−2. © 2014 Wiley Periodicals, Inc. J. Polym. Sci. Part B: Polym. Phys. 2014, 52, 587–595

Highly efficient deep blue light emitting devices based on triphenylsilane modified phenanthro[9, 10-d ]imidazole

Highly efficient deep blue fluorescent material (SiPIM) based on phenanthro[9, 10-d]imidazole (PPI) and triphenylsilane is designed and synthesized. SiPIM presents a narrow deep blue emission, high quantum yield, high thermal stability and good morphological stability. A non-doped vacuum-deposited device using SiPIM as active layer achieves an extremely high external quantum efficiency of 6.29% with true deep blue CIE coordinates of (0.163, 0.040). The solution-processed device is also tried due to the good solubility of SiPIM, which displays a maximum ηext of 2.40% and CIE coordinates of (0.157, 0.041).

Synthesis, characterization, physical properties, and blue electroluminescent device applications of phenanthroimidazole derivatives containing anthracene or pyrene moiety

By introducing a highly fluorescent anthracene, 9-(naphthalen-2-yl)anthracene or pyrene unit at the N1-phenyl of 1,2-diphenyl-1H-phenanthro[9,10-d]imidazole, three novel blue-emissive materials (ANPI, 2-NaNPI and PNPI) were synthesized and characterized, of which HOMO and LUMO orbitals are specifically segregative. Their high luminescence efficiency and excellent stability render them promising materials in electroluminescent device. The undoped three layers device using PNPI exhibits a maximum current efficiency of 4.99 cd A−1 with Commission Internationale d’Eclairage (CIEx,y) color coordinates of (x = 0.15, y = 0.17). Meanwhile, the property differences between N1-substituted and C2-substituted of diphenyl-1H-phenanthro[9,10-d]imidazole derivatives were studied. The results indicate that the change of conjugated position and moiety for those blue hosts can affect the electrical field polarization of device. Specifically, all the blue host materials containing anthracene moiety show an impressive luminous current efficiency around 12 cd A−1 when doped with sky blue fluorescent material BUBD-1.

ChemInform Abstract: Blue Fluorescent Emitters: Design Tactics and Applications in Organic Light‐Emitting Diodes

AbstractReview: 55 refs.