Synthesis and electrochemical characterization of a new polymer constituted of alternating carbazole and oxadiazole moieties

We report herein the synthesis and electrochemical characterization of a novel copolymer containing an electron rich carbazole moiety and an electron deficient oxadiazole unit—poly[N-(2′-ethylhexyl)-carbazole-3,6-diyl-1″,3″,4″-oxadiazole-2″,5″-diyl] (PCO). PCO can be dissolved in THF, CHCl₃, xylene, and DMSO. The structure of the polymer is confirmed by FT-IR, NMR and elemental analysis. The optical and electronic properties of the polymer are investigated by UV–Vis absorption spectroscopy and photoluminescence spectroscopy as well as cyclic voltammetry. The results show that the polymer films emit greenish-blue light (λ_max 485 nm) upon UV excitation. Both p-doping and n-doping processes are observed in cyclic voltammetric investigation. A comparison between the properties of polycarbazole and polycarbazole–oxadiazole has been presented.     

Synthesis and characterization of light-emitting materials composed of carbazole,pyrene and fluorene

A series of ethynyl-linked π-conjugated light-emitting molecules with good photoluminescence properties were designed and synthesized through Pd/Cu-catalyzed Sonogashira coupling reaction. The main structure comprised of different fluorophors (pyrene, carbazole, and fluorene), which were linked with triple bonds in order to be screened for high emission efficiency. Optical properties of these synthesized compounds (I_a–I_f) were examined in solutions, thin films and solid states, respectively. All of them showed relative high quantum yields both in solutions (Φ_s: 0.70–0.83) and in films (Φ_f: 0.17–0.34). Light-emitting diode using I_e as an emissive layer was fabricated in the ITO/poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT:PSS)/I_e/2, 2′, 2″-(1, 3, 5)-benzene-triyl)tris[1-phenyl-1H-benzimidazole] (TPBI)/Al configuration. The maximum emission wavelength of the device was 496 nm. The maximum luminance and electroluminescence efficiency was 1000 cd/m² and 0.41%, respectively.     

Synthesis of thermally stable and hole-transporting amorphous molecule having four carbazole moieties

A novel thermally stable and hole-transporting amorphous molecule, 9,9-bis(4-[bis-(4′-carbazol-9-yl-biphenyl-4-yl)-amino]-phenyl)fluorene (T-Caz) has been synthesized in two-step reactions from carbazole. T-Caz showed UV–Vis absorption bands at 290 and 340 nm in chloroform solution, and the photoluminescence spectrum showed a maximum peak at 420 nm in a purplish blue region. Differential scanning calorimetry (DSC) showed a high glass transition temperature at 250 °C. The organic light-emitting device prepared by spin-coating T-Caz solution onto the indium-tin oxide (ITO)-coated glass substrate in conjunction with tris(8-quinolinolato)aluminum (Alq) and LiF/Al, as an electron transporting light-emissive layer and a metal cathode, respectively, showed a maximum luminescence of 10,300 cd/m² at 11 V.     

Polarized light emission from aligned luminescent liquid crystal films based on 4,7-disubstituted-2,1,3-benzothiadiazoles

The physical properties of a series of light emitting liquid crystal compounds based on 4,7-disubstituted-2,1,3-benzothiadiazoles were investigated in thin solid films. The films were produced on glass plates via spin-coating and then heated to give their liquid crystal mesophases leading to an anisotropic organization of the molecules inside the films after subsequent cooling down to the room temperature. An important finding was that the induced film anisotropy exhibited photo-emission of polarized light. The absorption and fluorescence spectra of the heated films had significant differences compared to the non-heated ones and interesting differences in the organization of the molecules were observed when the films were deposited on anisotropic substrates. Optical microscopy and atomic force microscopy (AFM) measurements were performed to investigate the texture and morphology of the films.     

Synthesis and characterization of new electroluminescent molecules containing carbazole and oxadiazole units

The synthesis of new molecules containing both electron and hole transporter units is reported. This class of compounds, named OC, may be used for assembling electroluminescent devices made by a single organic layer. The active moieties are the carbazole, as the hole transporter unit, and the oxadiazole, as the electron transporter unit. The chemical formulation and the complex geometry of the molecular frame allow good solubility in chlorinate solvents and the preparation of homogeneous films by spinning technique.Photoluminescence of molecules, both in solution and in film, occurs in the blue region of visible spectra, the exact peak position of emission depending on the pendants attached to the oxadiazole unit. The electroluminescence occurs in a higher wavelength region, with a blue-green emission. The electroluminescent devices consist in the simple sequence ITO–OC–Al and ITO–PEDOT–OC–Al.     

Synthesis and characterization of red phosphorescent-conjugated polymers containing charged iridium complexes and carbazole unit

A series of homogeneous red-light phosphorescent polymers with charged iridium (Ir) complex in the backbones and carbazole unit on the side were synthesized by Suzuki polycondensation. These polymers are made up of three repeat units: (i) charged iridium (Ir) complex; (ii) 9,9-dihexylfluorene; (iii) 9,9-bis(N-carbazolyl-hexanyl)-fluorene. Their structures have been identified by nuclear magnetic resonance (NMR) and elemental analysis. All chelating polymers displayed good thermal stability, redox reversibility and film formation. Compared with our former study on these charged Ir complex containing polymers, the addition of carbazole unit has a strong influence on their hole injection and charge attraction ability as well as the host–guest energy transfer efficiency.     

均匀沉淀法制备铝酸锶发光材料及其性能

采用均匀沉淀法制备铝酸锶基质长余辉发光材料.用热重分析仪(TG)、红外光谱仪(IR)、X射线衍射仪(XRD)、扫描电镜(SEM)和荧光分光光度计对前驱体沉淀产物和焙烧样品进行表征.结果表明:前驱体沉淀产物主要是SrCO3和无定形Al(OH)3.经过熔烧后,未添加硼酸的样品为单一的SrA12O4相;添加0.3 mol 硼酸的样品为SrA12O4和Sr4Al14O25相共存;添加0.8 mol硼酸的样品中,SrA12O4相消失,仅有Sr4Al14O25相存在.与不加硼酸的样品相比,添加硼酸的样品的焙烧温度降低,晶粒长大,激发光谱和发射光谱强度增强,并且发射光谱发生了蓝移,余辉强度和时间也明显增加.但是过量的硼酸加入会降低材料的发光强度.     

Synthesis and characterization of mesoporous Mn-MCM-41 materials

MCM-41 has been synthesized at two different pH using cetyl-trimethylammonium bromide (CTAB) surfactant as template and adding the silica precursor to aqueous solutions containing CTAB. The obtained solids were calcined at 600 °C for 4 h. Mn-MCM-41 powders with different Mn/Si molar ratios were prepared using the incipient wetness method, followed by calcination at 550 °C for 5 h. At the end of the impregnation process the powders colour changed from white to brown whose intensity depends on manganese quantity. The materials characterization was performed by X-ray diffraction, N₂ adsorption, ²⁹Si Cross Polarization-Magic Angle Spinning NMR, and X-ray Photoelectron Spectroscopy. The effects of the manganese quantity and of the structural characteristic of the MCM-41 support were studied. The catalytic activity of the prepared systems was evaluated in a complete n-hexane oxidation.     

Synthesis and characterization of low molecular weight photorefractive materials with thioxanthene unit

Two esters of succinic acid containing a thioxanthene unit as an electron-transporting moiety and a 4-dicyanovinylaniline (THEH-DCVA) or 4-nitrovinylaniline unit (THEH-NVA) as an electro-optically (EO) active chromophore were successfully synthesized. The obtained succinates form stable amorphous films at room temperature. These compounds have absorption coefficients of 6.7 and 21.5 cm⁻¹ at 633 nm and glass transition temperatures of 11 and 14 °C for THEH-DCVA and THEH-NVA, respectively. Optical absorption is due to electric charge transfer interaction between an electron-accepting thioxanthene moiety and an electron-donating EO active chromophore. The synthesized compounds without photosensitizers, a plasticizer, and polymer binder showed photorefractivity. A large coupling gain (140 cm⁻¹ at 93 V/μm) was observed for THEH-NVA.     

Synthesis and characterization of dendritic poly(l-lysine) containing porphyrin–fullerene moieties

Amphiphilic l-lysine dendrons containing porphyrin and fullerene bearing amino acids with the ratio of 2:0, 2:1 and 1:1 were synthesized and characterized using UV–visible absorption spectroscopy, fluorescence emission spectroscopy and transmission electron microscopy. Photoluminescence spectra of these dendrimers showed photoluminescence quenching due to photoinduced electron transfer from porphyrin to fullerene moieties. Transmission electron microscopic observation evidenced the self-association of these dendrimers in water. Controllable and reversible dissociation and re-aggregation of some of the water soluble dendrimers have been investigated using electronic absorption and fluorescence spectra upon the addition of 2-hydroxypropyl-β-cyclodextrin and 1-adamantanecarboxylic acid in their aqueous dispersion. Enhanced ellipticity of dendritic porphyrin–fullerene conjugate compared to that only dendritic porphyrin indicates intramolecular porphyrin–fullerene interactions.     

Synthesis and characterization of a novel fullerene derivative containing carbazole group for use in organic solar cells

A novel carbazole-group-containing fullerene derivative (CBZ-C₆₀) with good solubility in common organic solvents was synthesized. This derivative was analyzed by using many techniques such as NMR, FAB-MS, FTIR and UV–vis absorption spectroscopy. Further, bulk heterojunction photovoltaic devices were fabricated. Since the LUMO energy level of CBZ-C₆₀ was higher than that of fullerene, the open-circuit voltage (V_oc) of devices based on CBZ-C₆₀ was higher than that of devices based on fullerene. The power-conversion efficiency was highest for devices with composite thin films that have P3HT/CBZ-C₆₀ composition ratios of 1:1 and were annealed at 150 °C for 10 min. The maximum V_oc, short-circuit current density, and PCE of the best device were 0.64 V, 2.32 mA/cm², and 0.48%, respectively.     

Synthesis and characterization of triphenylamine–benzothiazole-based donor and acceptor materials

A series of π-conjugated compounds were successfully synthesized by varying ratios of triphenylamine as donor (D) and benzothiazole as acceptor (A). The structure–property relationship about photoluminescence based on these synthesized compounds was systematically discussed in detail. Quantum chemical calculations were used to obtain optimized ground-state geometry by hybrid density functional theory (B3LYP) with 6-31G* basis set, spatial distributions of the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO) levels of the compounds. As expected, these compounds exhibit high extinction coefficients, high quantum yields, and excellent thermal stability properties. The optical properties clearly indicate that the fluorescent emission properties of these compounds rely largely on the molecular structure.     

A highly efficient deep blue fluorescent OLED based on diphenylaminofluorenylstyrene-containing emitting materials

We have designed and synthesized five blue emitters based on diphenylaminofluorenylstyrene emitting core groups. Multilayered OLEDs were fabricated using these materials as dopants in a 2-methyl-9,10-di(naphthen-2-yl)anthracene (MADN) host. One of them in particular a deep blue OLED using dopant 9-[4-(2-diphenylamino-9,9-diethylfluoren-7-yl)phenyl]-9-phenylfluorene (3) at 15% doping concentration exhibited a maximum luminance of 4720 cd m^?2 at 9.0 V, a luminous efficiency of 5.3 cd A^?1 at 20 mA cm^?2, a power efficiency of 2.9 lm W^?1 at 20 mA cm^?2, an external quantum efficiency of 4.8% at 20 mA cm^?2, and CIE coordinates (x = 0.15, y = 0.13) at 8.0 V. Furthermore, this deep blue device had very stable CIE coordinates of (x = 0.15, y = 0.13) that did not vary with doping concentration from 5% to 15%.     

Synthesis of new hole-transporting molecular glass with pendant carbazolyl moieties

The synthesis and properties of amorphous hole-transporting 4,4′-bis[11-carbazol-9-yl)-6,8,10-tri(carbazol-9-methyl)-3-hydroxy-5,7,9-trioxa-1-thia]thiobisbenzene with two end and six pendant carbazolyl moieties, separated from the main chain by CH₂ spacers, is reported. It was prepared by a multistep synthesis route from 1,6-di(carbazol-9-yl)-5-(carbazol-9-methyl)-4-oxa-2-hexanol glycidyl ether. Glass transition temperatures of intermediate and final products established by differential scanning calorimetry are reported. The hole drift mobility, measured by the time of flight technique, in this well defined molecular glass depends little on the strength of the electric field and exceeds 10⁻⁵ cm² V⁻¹ s⁻¹. The ionization potentials measured by electron photoemission method, light absorption and fluorescence spectra are closed to those reported for the other organic photoconductors containing electronically isolated carbazole moieties.     

Synthesis and characterization of the carbon nanotube-based composite materials with poly(3,4-ethylenedioxythiophene)

We report a procedure to prepare a conducting nano-composites composed of multi-walled carbon nanotubes (MWNTs) and PEDOT by using a poly(sodium 4-styrenesulfonate) (PSSNa) as a inter-linking molecule between MWNT and PEDOT. When PSSNa chains are introduced on the MWNTs via physicochemical interaction, the surface of MWNT becomes negatively charged, and PSS-modified MWNTs promote the effective association of the positively charged PEDOT chains. The resulting MWNT-PSS/PEDOT composites are characterized by a better interconnection between MWNT and PEDOT components.     

La2O3:Sm3+纳米发光材料的燃烧法合成及其性能研究

通过燃烧法制备了La2O3:Sm3+纳米材料,用XRD和TEM对其形貌结构进行了表征和分析,并研究了其发光性质。结果表明：La2O3:Sm3+纳米材料为六角结构,颗粒尺寸大约为34 nm; Sm3+的掺杂引起其衍射峰的位置发生略微的右移; Sm3+的本征激发带位于411 nm左右;在近紫外光（411 nm）的激发下,观察到 4G5/2 → 6H5/2 (568 nm)、 4G5/2 → 6H7/2 (611 nm, 强度最高) 和 4G5/2 → 6H9/2 (654 nm)三个主发射峰;发射光谱表明La2O3:Sm3+中Sm3+离子的格位对称性较低;材料样品的衰减寿命约为202 us,色度坐标大约为(0.5849, 0.4143)。     

Synthesis and electroluminescence of thiophene-based bipolar small molecules with different arylamine moieties

A series of fluorescent dyes consisted of a thiophene unit, an 1,3,4-oxadiazole unit and four different arylamine moieties were prepared using a facile multi-steps synthetic route with high yield. The four arylamine structures studied were triphenylamine, N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine, diphenyl(1-naphthyl)amine and 9-phenylcarbazole. Experimental results shown that their HOMOs varied from 5.21 to 5.73 eV strongly affected by the arylamine chemistry while their LUMOs remained relatively unchanged. Their corresponding emission colors ranged from UV (393 nm) to bluish green (483 nm). In general, the thiophene unit enhanced the overall thermal stability of the compounds. According to cyclic voltammetry, the compounds are predominantly hole-transporting while OLED results indicated cpd 10 possess both hole and electron transport properties. Single layer OLED fabricated from 10 resulted in ca. 2000 cd/m² (luminous intensity) and 1.10 cd/A (current efficiency) max, whereas, a multilayer OLED using 10 as the hole transporting layer achieved over 7400 cd/m² and 2.3 cd/A max.     

Synthesis and photophysical properties of host materials with high triplet energy based on dibenzofuran and triphenylamine functionalities

A host material with high triplet energy based on dibenzofuran and triphenylamine interconnected through diphenylmethylene linkage was synthesized and photophysical properties of the host material were investigated. A high triplet energy of 2.90 eV was obtained due to complete separation of an electron donating triphenylamine and accepting dibenzofuran by diphenylmethylene linkage. It was found out that intermolecular charge transfer dominated the light emission of the host material.     

Synthesis of new hole-transporting molecular glasses with pendant carbazolyl-based hydrazone moieties

Synthesis, thermal, optical and photoelectrical properties of new hole-transporting molecular glasses with pendant carbazolyl-based hydrazone moieties, linked by aliphatic linking fragments, are reported. Electron photoemission spectra of the synthesized derivatives have been recorded and the ionization potentials have been established. The hole drift mobility values in compositions of the designed structures with bisphenol Z polycarbonate exceed 10^?5 cm² V^?1 s^?1 at an electric field 10⁶ V/cm.     

Synthesis and characterization of efficient orange-red emitting poly(p-phenylenevinylene) derivatives with 1,3,4-oxadiazole unit

A series of the statistical copolymers of tetradecyloxy-3,5-bis-{2-(4-bromo-phenyl)-[1,3,4]oxadiazole}-benzene (4), 1,4-didecyloxy-2,5-diiodobenzene (5) and 1,4-dodecyloxy-2,5-divinylbenzene (6), for efficient light emitting diode were synthesized. As the feed ratio of compound 4 decreased, the absorption band at 320–360 nm decreased in the UV–vis spectra. In addition, as the composition of compound 4 decreased, the absorption intensity ratio at 1541 cm⁻¹ decreased in the FT-IR spectra. The photoluminescence and electroluminescence emission color of P showed green-yellow color (λ_max = 552 nm). However, the maximum wavelength of photoluminescence and electroluminescence of P1 and P2 were 581 and 583 nm, respectively, which were dramatically red-shifted than that of P. Moreover, these values were almost the same as the values of P3 (580 nm). It is concluded that the energy transfer from high energy oxadiazole segments to low energy alkoxy-PPV segments occurred completely. The efficiency of ITO/P2/Al was 0.0181%, which is the best efficiency among the device based on the copolymers. This is presumably due to that P2 has the best balanced hole- and electron-injection/transporting properties among the copolymers.