Four novel polymers, poly(3,6-9-decyl-carbazole-alt-1,3-benzene)(PB13CZ), poly(3,6-9-decyl-carbazole-altbis(4-phenyl)(phenyl) phosphine oxide)(PTPPO38CZ), poly(3,6-9-decyl-carbazole-alt-2,4-phenyl(diphenyl) phosphine oxide)(PTPPO13CZ) and poly(3,6-9-decyl-carbazole-alt-bis(3-phenyl)(phenyl) phosphine oxide)(PTTPO27CZ) were synthesized, and their thermal, photophysical properties and device applications were further investigated to correlate the chemical structures with the photoelectric performance of bipolar host materials for phosphorescent organic light emitting diodes. All of them show high thermal stability as revealed by their high glass transition temperatures and thermal decomposition temperatures at 5% weight loss. These polymers have wide band gaps and relatively high triplet energy levels. As a result, the spin coating method was used to prepare the green phosphorescent organic light emitting diodes with polymers PTPPO38 CZ, PTPPO13 CZ and PTTPO27 CZ as the typical host materials. The green device of polymer PTPPO38 CZ as host material shows electroluminescent performance with maximum current efficiency of 2.16 cd·A~(-1), maximum external quantum efficiency of 0.7%, maximum brightness of 1475 cd·m~(-2) and reduced efficiency roll-off of 7.14% at 600 cd·m~(-2), which are much better than those of the same devices hosted by polymers PTTPO27 CZ and PTPPO13 CZ. 相似文献
We present a novel core-shell-surface multifunctional structure for dendrimers using a blue fluorescent pyrene core with triphenylene dendrons and triphenylamine surface groups. We find efficient excitation energy transfer from the triphenylene shell to the pyrene core, substantially enhancing the quantum yield in solution and the solid state (4-fold) compared to dendrimers without a core emitter, while TPA groups facilitate the hole capturing and injection ability in the device applications. With a luminance of up to 1400 cd/m(2), a saturated blue emission CIE(xy) = (0.15, 0.17) and high operational stability, these dendrimers belong to the best reported fluorescence-based blue-emitting organic molecules. 相似文献
We synthesized a series of novel spiro[fluorene-9, 9'-xanthene] (SFX)-based host materials via a one-step palladium-catalyzed cross-coupling reaction. These materials have high triple energy levels and high yield, and thus can be used as hosts for blue phosphors. Blue phosphorescent organic light-emitting devices (PHOLEDs) with a bis (3, 5-difluoro-2-(2-pyridyl) phenyl-(2-carboxypyri-dyl) iridium (Ⅲ) (FIrpic) emission were fabricated. Furthermore, we applied cohosts composed of one of the new synthesized materials and the hole transport material di-[4-(N, N-ditolyl-amino)-phenyl]cyclohexane (TAPC) to the blue PHOLEDs to successfully acquire efficient blue emissions. The SFX-based material provided efficient energy transfer while TAPC improved the mobility of the cohost as well as reduced the working voltage. Maximum current efficiencies of 22.56 and 25.93 cd·A-1 and the maximum brightnesses of 6421 and 6196 cd·m-2 were obtained for the PHOLEDs with TAPC: 2-(9-phenyl-fluoren-9-yl) spiro[fluorene-9, 9'-xanthene] (PF-SFX) and TAPC: 2-(9-(4-(octyloxy)-phenyl)-9H-fluoren-9-yl) spiro[fluorene-9, 9'-xanthene] (C8OPF-SFX) cohosts, respectively. The experimental results obtained for the four SFX-based host materials were enough to declare that SFX is an effective main unit that can be used to build efficient host materials for blue phosphors containing only C, H, and O basic elements. 相似文献
A range of dendritic molecules was made using the monodentate SEMI-ESPHOS phosphine oxide ligand, which was derivatised with a series of functional groups including bromide, vinyl, allyl and terminal alkyne. Several methods to attach the resulting precursors onto octavinylsilsesquioxane (OVS), ranging from hydrosilylation, Suzuki, Heck, Grubbs or Sonogashira coupling reactions, have been investigated. Cross-metathesis of SEMI-ESPHOS oxide dendrons containing vinyl end groups with OVS catalyzed by Grubbs' catalyst was proven to be effective in the formation of precursors for dendritic molecules based on OVS. 相似文献
Synthesis and characterization of dendrimers containing thienylbenzene repeating units, red-emitting benzothiadiazole core, and triarylamine peripheries that bear naphthyl units are reported. The relevant dendrimers of different generations are classified as G(nb) (n=1-3), while the tert-butyl dendrimers G(na) with the acceptor alone were also synthesized to serve as control chromophores that avoid donor-acceptor interactions. The resulting dendrimers are capable of harvesting photon energy through efficient energy transfer among donor-acceptor moieties, so that highly luminescent red fluorophores result. Transient fluorescence studies suggest that the energy transfer and its efficiency are approximately unity in all G(a) dendrimers, whereas the rate of energy transfer for the G(b) dendrimers is suppressed, that is, charge transfer from the core to the periphery is a significant quenching pathway. These dendrimers are amorphous in nature with high glass transition temperatures (176-201 degrees C). Electroluminescent devices were fabricated by using the dendrimers as hole-transporting emitters, and the devices exhibit promising red emission parameters. 相似文献
Using a shielded growth approach and N2-annealed, nearly monodispersed Fe2O3 nanoparticles synthesized by interdendritic stabilization of Fe3+ species within fourth-generation poly(amidoamine) dendrimers, carbon nanotubes and nanofibers were successfully grown at low substrate temperatures (200-400 degrees C) by microwave plasma-enhanced chemical vapor deposition. 相似文献
Summary: A new family of solution‐processable, photoluminescent, nanocomposite dendrimers based on cyclic phosphazene (CP) cores have been prepared and characterized. The synthetic approach is based on the preparation of bromoaromatic‐functionalized CP cores by reacting selected bromophenolic compounds with the commercially available hexachlorocyclotriphosphazene in yields >90%. The bromophenyl‐functionalized CP cores are then reacted with N‐p‐tolylpyren‐1‐amine using Buchwald‐Hartwig amination chemistry to give the dendrimers of interest in yields >90%. The resultant dendrimers have high glass transition (>165 °C) and decomposition temperatures (>465 °C), are monodisperse (PDI < 1.05), have high purity via common chromatographic techniques, have high photoluminescent quantum efficiencies (83%), and form defect‐free amorphous films via spin/dip coating. A comparison to their molecular analogues is also provided to demonstrate the superior properties of the new nanocomposite dendrimers.
Structure of the cyclic phosphazene dendrimers. 相似文献
A series of alkali metal salts doped pluronic block copolymer F127 were used as electron injection/transport layers (ETLs) for polymer light-emitting diodes with poly[2-(4-(3′,7′-dimethyloctyloxy)-phenyl)-p-phenylenevinylene] (P-PPV) as the emission layer. It was found that the electron transport capability of F127 can be effectively enhanced by doping with alkali metal salts. By using Li2CO3 (15%) doped F127 as ETL, the resulting device exhibited improved performance with a maximum luminous efficiency (LE) of 13.59 cd/A and a maximum brightness of 5529 cd/m2, while the device with undoped F127 as ETL only showed a maximum LE of 8.78 cd/A and a maximum brightness of 2952 cd/m2. The effects of the doping concentration, cations and anions of the alkali metal salts on the performance of the resulting devices were investigated. It was found that most of the alkali metal salt dopants can dramatically enhance the electron transport capability of F127 ETL and the performance of the resulting devices was greatly improved. 相似文献
Building a new structual oligo(phenylenevinylene) by linking trimeric phenylenvinylene (TPV) through the phenylphenyl bond of a central phenylene ring was reported. The resultant TPV dimers exhibit weak intermolecular interactions and intense blue photoluminescence in the solid state as well as high phase transition temperatures up to 250 degrees C. Organic light-emitting devices (OLEDs) based on these materials display blue emission with low turn-on voltage (about 3 V), maximum luminance approaching 2000 cd m(-2) and efficiency up to 1.6 cd A(-1). 相似文献
New CN donor ligands incorporating pyridine or benzoimidazole N donors and a sterically hindered cyclometalating aromatic core featuring a polyphenylenephenyl, fluoranthene, or triphenylene segment are prepared and successfully converted into heteroleptic iridium(III) cyclometalated complexes with acetylacetone auxiliary ligands. The X-ray structure of the complex, derived from a ligand containing a fluoranthene fragment, has been solved to unveil the corresponding structure. The results clearly demonstrate that the nature of the sigma-coordinating ligand segment plays a key role in dictating the emission profile and peak position, such that the emission hue has been successfully tuned ranging from green to red. Supplementary support of this viewpoint is also rendered by computational (DFT) approaches. Electroluminescent devices fabricated using a complex as dopant in the PVK matrix were found to exhibit bright greenish yellow emission with promising device characteristics (maximum brightness 26450 cd m(-2) at 30 V and a maximum current efficiency of 40 cd A(-1)). 相似文献
A new series of Os(II) diimine complexes with the general formula [Os(N(wedge)N)(CO)(2)I(2)], N(wedge)N = 2,2'-bipyridine (bpy) (1), 4,4'-di-tert-butyl-2,2'-bipyridine (dbubpy) (2), 4,7-diphenyl-1,10-phenanthroline (dpphen) (3), 2-(2'-pyridyl)benzoxazole (pboz) (4), and 5-tert-butyl-2-(2'-pyridyl)benzoxazole (bupboz) (5), were synthesized and characterized by spectroscopic methods and by a single-crystal X-ray diffraction study on the dpphen complex 3. The corresponding photophysical properties were studied using UV-vis and emission spectrometry. The resulting phosphorescence features both in solution and as a solid film, in combination with the MO calculation, lead us to conclude that the emissions originate from mixed halide-to-ligand (XLCT approximately 70%) and metal-to-ligand (MLCT approximately 30%) transitions instead of the typical MLCT transition. Using complexes 4 and 5 as the dopant emitters, we evaluated their potential to serve as a phosphor for organic light emitting diodes by examining their electroluminescent performances. Reddish orange electroluminescence centered around 600 nm was observed for organic light emitting diodes (OLEDs) fabricated using complex 5 as the emitter; the device efficiency was shown to be as high as 2.8% (and 5.0 cd/A or 2.7 lm/W), and the peak luminance was shown to be 5600 cd/m(2) at a driving voltage of approximately 15 V. 相似文献
Large dendrimers, noted G(n)-3(n+2)cage, containing 3(n+2) o-carborane cluster cages MeC(2)B(10)H(10) at their peripheries (n = number of generation noted G(n)) have been synthesized by Huisgen-type azide alkyne Cu(I)-catalyzed dipolar "click" cycloaddition reactions (CuAAC) between an o-carborane monomeric cluster containing an ethynyl group and arene-centered azido-terminated dendrimers G(n)-3(n+2)N(3) of generations 0, 1, and 2. Attempts to synthesize higher-generation dendrimers of this family yielded insoluble materials. The carborane dendrimers G(0)-9cage, G(1)-27cage, and G(2)-81cage have been characterized by (1)H, (13)C, (11)B NMR, elemental analysis, matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectroscopy, and size exclusion chromatography (SEC) showing low polydispersities, dynamic light scattering (DLS) showing hydrodynamic diameters of 5.7 nm for the G(1)-27cage and the 12.9 nm for the G(2)-81cage. These dendrimers are extremely robust thermally, with 10% mass loss temperatures of 411 °C for the G(0)-9cage, 371 °C for the G(1)-27cage, and 392 °C for the G(2)-81cage. They all showed a strong absorption in the UV region peaking at 258 nm, whereas emission spectra of low intensities were observed between 280 and 480 nm. 相似文献
Control of particle-particle spacing is a key determinant of optical, electronic, and magnetic properties of nanocomposite materials. We have used poly(amidoamine) (PAMAM) dendrimers to assemble carboxylic acid-functionalized mixed monolayer protected clusters (MMPCs) through acid/base chemistry between the particle and dendrimer. Small angle X-ray scattering was then used to establish average inter-MMPC distances. Five generations of PAMAM dendrimer (0, 1, 2, 4, 6) were investigated, with a monotonic increase in interparticle spacing from 4.1 to 6.1 nm observed with increasing generation. 相似文献
This study reports substituent effects of iridium complexes with 1-phenylisoquinoline ligands. The emission spectra and phosphorescence quantum yields of the complexes differ from that of tris(1-phenylisoquinolinato-C2,N)iridium(iii)(Irpiq) depending on the substituents. The maximum emission peak, quantum yield and lifetime of those complexes ranged from 598-635 nm, 0.17-0.32 and 1.07-2.34 micros, respectively. This indicates the nature of the substituents has a significant influence on the kinetics of the excited-state decay. The substituents attached to phenyl ring have an influence on a stability of the HOMO. Furthermore, those substituents have effect on the contribution to a mixing between 3pi-pi* and (3)MLCT for the lowest excited states. Some of the complexes display the larger quantum yield than Irpiq, which has the quantum yield of 0.22. The organic light emitting diode (OLED) device based on tris [1-(4-fluoro-5-methylphenyl)isoquinolinato-C2,N]iridium(iii)(Ir4F5Mpiq) yielded high external quantum efficiency of 15.5% and a power efficiency of 12.4 lm W(-1) at a luminance of 218 cd m(-2). An emission color of the device was close to an NTSC specification with CIE chromaticity characteristics of (0.66, 0.34). 相似文献
Monolayer formation of two dendrimers containing a hydrophilic core group (COOH) and hydrophobic peripheral groups (anthracene and aryl ether tail groups), 4-{10-[4-(3,5-bis-benzyloxy)-phenyl]-anthracen-9-yl}-benzoic acid (G1) and 4-(10-{4-[3,5-bis-(3,5-bis-benzyloxy)-benzyloxy]-phenyl}-anthracen-9-yl)-benzoic acid (G2), were studied. To understand the mechanism of the self-assembly of these molecules, we measured the surface pressure-surface area (Pi- A) isotherm and investigated the surface texture of Langmuir-Blodgett monolayers transferred onto hydrophilic silicon wafers. Both dendrimers form circular domains at the onset point of surface pressure as a result of the difference in hydrophobicity between the core group and the peripheral end group. The core group has a functional group at the end of dendrimer and can be anchored on the water surface. Upon further compression, monolayer of G1 shows a domain of molecules whereas a monolayer of G2 is aligned in the direction of compression at 10 mN/m. At higher surface pressure (20 mN/m), G1 molecules have several aggregates of domains, but G2 molecules maintain their ordering. These results were confirmed by the electron density profile of G1 and G2 monolayers transferred to silicon substrates, as measured by X-ray reflectivity. 相似文献