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1.
The formation of ruptured poly[2‐methoxy‐5‐(2′‐ethyl‐hexyloxy)‐1,4‐phenyl vinylene] (MEH–PPV) thin films coated from undried tetrahydrofuran (THF) solutions was investigated. Because of the incompatibility of water and MEH–PPV, the polymer films coated from THF/water solutions showed a ruptured film structure. In the photoluminescence (PL) spectra of the polymer thin films, the ruptured polymer films showed a redshifted emission in comparison with continuous polymer thin films. According to a comparison of the PL spectra of polymer solutions and films, MEH–PPV in THF showed a coil–cylinder transition during precipitation from solution. Because of the incompatibility of water and MEH–PPV, an increase in the water content could increase the ratio of polymer chains in the cylinder conformation, resulting in a redshifted emission for the films. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 79–84, 2006  相似文献   

2.
In this study, luminescence electrospun (ES) nanofibers based on ternary blends of poly(9,9‐dioctylfluoreny‐2,7‐diyl) (PFO)/poly[2‐methoxy‐5‐(2‐ethylhexyloxy)‐1,4‐phenylenevinylene] (MEH‐PPV)/poly(methyl methacrylate) (PMMA) were prepared from chloroform solutions using a single capillary spinneret. Effects of PFO/MEH‐PPV ratio on the morphology and photophysical properties were studied while the PMMA weight percentage was fixed at 90 wt %. The morphologies of the prepared ES fibers were characterized by FE‐SEM and fluorescence microscopy. The obtained fibers had diameters around a few hundred nm and pore sizes in the range of 30–35 nm. The emission colors of the PFO/MEH‐PPV/PMMA blend ES fibers changed from blue, white, yellowish‐green, greenish‐yellow, orange, to yellow, as the MEH‐PPV composition increased. In contrast, the emission colors of the corresponding spin‐coated films were blue, orange, pink‐red, red, and deep‐red. Based on the values of solubility parameters, the PFO and MEH‐PPV are miscible to each other and trapped in the PMMA matrix. Hence, energy transfer between these two polymers is possible. The smaller aggregated domains in the ES fiber compared to those of spin‐coated films possibly reduce the efficiency of energy transfer, leading to different emission colors. Also, the prepared ES fibers had higher photoluminescence efficiencies than those of the spin‐coated films. Pure white light‐emitting fibers prepared from the PFO/MEH‐PPV/PMMA blend ratio of 9.5/0.5/90 had the Commission Internationale de L'Eclairage (CIE) coordinate of (0.33, 0.31). Our results showed that different color light‐emitting ES fibers were produced through optimizing the composition of semiconducting polymer in the transparent polymer matrix. This type of ES fibers could have potential applications as new light sources or sensory materials for smart textiles. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 463–470, 2009  相似文献   

3.
Polymer solar cells were fabricated based on composite films of poly(2‐methoxy‐5‐(2′‐ethyl‐hexyloxy)‐1,4‐phenylenevinylene) (MEH‐PPV):fullerene derivative (6,6)‐phenyl‐C61‐butyric acid methyl ester (PCBM) with weight blend ratio of 1:3, 1:4 and 1:5, spin‐coated from chloroform (CF), chlorobenzene (CB), and o‐dichlorobenzene (ODCB) solutions, respectively. Photoinduced current and power conversion efficiency (PCE) of the devices show a dependence on the solvents. The solar cells have the highest PCE at 1:5 blend ratio. Transmission electron microscopy (TEM) morphology reveals that there are some voids in MEH‐PPV:PCBM films. The void number decreases with the solvent from CF to CB and ODCB. We found the voids are located at the bottom of the films through electron tomography technique by TEM and film bottom‐side morphology study by atomic force microscopy. The charge carrier transport efficiency and collection efficiency should decrease greatly due to the voids, and the more voids the film has, the more degree the efficiencies decrease. PCE of the solar cell prepared from CF is lower than that of the solar cells prepared from CB and ODCB. The void phenomenon of MEH‐PPV:PCBM based solar cell and method to investigate the void position provide an experimental evidence and research mentality to fabricate polymer solar cell with high performance.  相似文献   

4.
With anodic alumina with an ordered nanopore array used as a template, poly[2‐metoxy‐5‐(2′‐ethyl‐hexyloxy)‐p‐phenylene vinylene] (MEH–PPV) was embedded into the nanopores, and then two‐dimensional arrays of light‐emitting nanopolymers were prepared. By the measurement and analysis of photoluminescence and photoluminescence excitation spectra of the samples, it was demonstrated that the optical properties of the nano‐MEH–PPV arrays were obviously different from those of MEH–PPV films. The conformations of the MEH–PPV chains in the nanopores, films, and solutions and their effects on the optical properties were examined. It was determined experimentally that the conformations of the MEH–PPV chains in the solutions were maintained in the nano‐MEH–PPV arrays. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3037–3041, 2006  相似文献   

5.
A series of white polymer light emitting displays (PLEDs) based on a polymer blend of polyalkylfluorenes and poly(2‐methoxy‐5,2′‐ethyl‐hexyloxy‐1,4‐phenylene vinylene) (MEH‐PPV) was developed. MEH‐PPV or red light emitting alkyfluorene copolymer (PFR) was blended with blue light emitting alkyfluorene copolymer (PFB), and MEH‐PPV was blended with both green light emitting alkyfluorene copolymer (PFG) and PFB to generate white light emission PLEDs. Low turn on voltage (2.7 V), high brightness (12,149 nits), high efficiency (4.0 cd/A, 4.0 lm/W), and good color purity (Commission Internationale de L'Eclairage (CIEx,y) co‐ordinates (0.32, 0.34)) were obtained for the white PLEDs based on the PFB and MEH‐PPV polymer blend. Exciplex formation in the interface between PFR and PFB induced a new green emission peak for these two components based white PLEDs. As a result, strong white emission (4078 nits) was obtained by mixing the red, green, and blue (RGB) three primary colors. High color purity of blue (CIE, x = 0.14, y = 0.08), green (CIE, x = 0.32, y = 0.64) and red (CIE, x = 0.67, y = 0.33) emissions was achieved for white PLEDs combining with dielectric interference color‐filters. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 330–341, 2007  相似文献   

6.
The surface morphology of thin molecularly imprinted polymer films has been studied using atomic force microscopy (AFM). The films were produced by spin coating onto glass substrates and examined as a function of host polymer, imprinting template, casting solvent, spin‐coater rotation speed and post‐production treatment. It was observed that the gross features of such films are template controlled. The fine structure is determined by parameters such as solvent, spin speed or subsequent treatment. The relationship between these observations, polymer–template interactions and the mechanism of film formation in spin coating is discussed. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

7.
Three novel copolyfluorenes ( P1 ‐ P3 ) containing pendant bipolar groups (2.5–7.7 mol %), directly linked hole‐transporting carbazole and electron‐transporting aromatic 1,2,4‐triazole, were synthesized by the Suzuki coupling reaction and applied to enhance emission efficiency of polymer light‐emitting diodes based on conventional MEH‐PPV. The bipolar groups not only suppress undesirable green emission of polyfluorene under thermal annealing, but also promote electron‐ and hole‐affinity of the resulting copolyfluorenes. Blending the bipolar copolyfluorenes with MEH‐PPV results in significant enhancement of device performance [ITO/PEDOT:PSS/MEH‐PPV+ P1 , P2 or P3 /Ca(50 nm)/Al(100 nm)]. The maximum luminance and luminance efficiency were enhanced from 3230 cd/m2 and 0.29 cd/A of MEH‐PPV‐only device to 15,690 cd/m2 and 0.81 cd/A (blend device with MEH‐PPV/ P3 = 94/6 containing about 0.46 wt % of pendant bipolar residues), respectively. Our results demonstrate the efficacy of the bipolar copolyfluorenes in enhancing emission efficiency of MEH‐PPV. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011  相似文献   

8.
The surface sheet resistance of conducting films of glycerol‐doped poly(3,4‐ethylenedioxy‐thiophene)–poly(styrene sulfonate) is largely dependent on the annealing temperature. The presence of free glycerol in insufficiently baked films, as indicated by infrared spectra and thermogravimetric analysis, results in conducting polymer films with poor morphology and low electrical conductivity. The device performance of organic light‐emitting diodes using this modified poly(3,4‐ethylenedioxy‐thiophene)–poly(styrene sulfonate) as an anode is also greatly affected by the baking conditions of the conducting films. The maximum light output, current density, and luminous power efficiency are observed from devices using anodes baked at a high temperature close to the boiling point of glycerol. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2522–2528, 2003  相似文献   

9.
Hybrid polymer films consist of quantum dots (QDs) dispersed in a polymer matrix. A key fundamental challenge that is hindering their optimisation in optoelectronic devices such as hybrid solar cells is overcoming uncontrolled aggregation of the QDs. In an effort to direct aggregation, and trigger self-assembly, we added a bilinker ligand (1,2-ethanedithiol) to dispersed PbS QDs in polymer solutions prior to film deposition by spin casting. Turbidity studies of the PbS QD/1,2-ethanedithiol dispersions enabled a relationship to be established between the extent of 1,2-ethanedithiol-triggered QD aggregation and the nominal fractional coverage of the QDs by 1,2-ethanedithiol. The extent of aggregation (and self-assembly) increased with nominal fraction coverage. Above a value of about 1.0 QD aggregation increased substantially. TEM images showed that at low 1,2-ethanedithiol concentrations triggered assembly of network-like QD structures occurred. At high 1,2-ethanedithiol concentrations the QDs self-assembled into more-ordered micrometre-sized crystals. The results suggest that 1,2-ethanedithiol decreases the inter-QD separation in dispersion as a result of rapid ligand exchange and this process results in QD aggregation as well as self-assembly. The assembled QD structures were successfully trapped within polymer films by spin casting of PbS QD/1,2-ethanedithiol dispersions containing added polystyrene or polytriarylamine.  相似文献   

10.
Homogenously dispersed organic (MEH‐PPV)/inorganic (nanosized titania) hybrids were successfully synthesized. The method of preparation was based on a simple one‐step in situ sol–gel technique using titanium isopropoxide (TIP) as the precursor. The key benefit of this preparation was that TIP interacted with both 2‐chlorophenol and MEH‐PPV, so that the degree of aggregation and phase separation could be kept to a minimum with a suitable recipe. MEH‐PPV/TIP/H2O/2‐chlorophenol of various weight ratios were synthesized to examine the morphology as well as optical properties of the MEH‐PPV/TIP(titania) hybrid. The observation of MEH‐PPV gelation and Fourier transform infrared results verified the interaction existing between MEH‐PPV and TIP. SEM photographs showed that TIP(titania) were homogenously dispersed in the MEH‐PPV film if the hybrid solution was clear from the use of a suitable recipe. UV–vis absorption measurements showed that the addition of TIP decreased the conjugation length of MEH‐PPV. A redshift in the photoluminescence (PL) emission was observed in almost all the hybrids in the solution state, because of the aggregation of MEH‐PPV. However, it was found that spinning destroyed the aggregation of MEH‐PPV, resulting in a blueshift in the PL emission of the hybrids. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 515–529, 2008  相似文献   

11.
Photophysical processes in conjugated polymers are influenced by two competing effects: the extent of excited state delocalization along a chain, and the electronic interaction between chains. Experimentally, it is often difficult to separate the two because both are controlled by chain conformation. Here we demonstrate that it is possible to modify intra‐chain delocalization without inducing inter‐chain interactions by intercalating polymer monolayers between the sheets of an inorganic layered matrix. The red‐emitting conjugated polymer, MEH‐PPV, is confined to the interlayer space of layered SnS2. The formation of isolated polymer monolayers between the SnS2 sheets is confirmed by X‐ray diffraction measurements. Photoluminescence excitation (PLE) and photoluminescence (PL) spectra of the incorporated MEH‐PPV chains reveal that the morphology of the incorporated chains can be varied through the choice of solvent used for chain intercalation. Incorporation from chloroform results in more extended conformations compared to intercalation from xylene. Even highly twisted conformations can be achieved when the incorporation occurs from a methanol:chloroform mixture. The PL spectra of the MEH‐PPV incorporated SnS2 nanocomposites using the different solvents are in good agreement with the PL spectra of the same solutions, indicating that the conformation of the polymer chains in the solutions is retained upon intercalation into the inorganic host. Therefore, intercalation of conjugated polymer chains into layered hosts enables the study of intra‐chain photophysical processes as a function of chain conformation.  相似文献   

12.
Novel conjugated polyfluorene copolymers, poly[9,9‐dihexylfluorene‐2,7‐diyl‐co‐(2,5‐bis(4′‐diphenylaminostyryl)‐phenylene‐1,4‐diyl)]s (PGs), have been synthesized by nickel(0)‐mediated polymerization from 2,7‐dibromo‐9,9‐dihexylfluorene and 1,4′‐dibromo‐2,5‐bis(4‐diphenylaminostyryl)benzene with various molar ratios of the monomers. Because of the incorporation of triphenylamine (TPA) moieties, PGs exhibit much higher HOMO levels than the corresponding polyfluorene homopolymers and are able to facilitate hole injection into the polymer layer from the anode electrode in light‐emitting diodes. Conventional polymeric light‐emitting devices with the configuration ITO/PEDOT:PSS/polymer/Ca/Al have been fabricated. A light‐emitting device produced with one of the PG copolymers (PG10) as the emitting layer exhibited a voltage‐independent and stable bluish‐green emission with color coordinates of (0.22, 0.42) at 5 V. The maximum brightness and current efficiency of the PG10 device were 3370 cd/m2 (at 9.6 V) and 0.6 cd/A, respectively. To realize a white polymeric light‐emitting diode, PG10 as the host material was blended with 1.0 wt % of a red‐light‐emitting polymer, poly[9,9‐dioctylfluorene‐2,7‐diyl‐alt‐2,5‐bis(2‐thienyl‐2‐cyanovinyl)‐1‐(2′‐ethylhexyloxy)‐4‐methoxybenzene‐5′,5′‐diyl] (PFR4‐S), and poly[2‐methoxy‐5‐(2′‐ethylhexyloxy)‐1,4‐phenylenevinylene] (MEH‐PPV). The device based on PG10:PFR4‐S showed an almost perfect pure white electroluminescence emission, with Commission Internationale de l'Eclairage (CIE) coordinates of (0.33, 0.36) at 8 V; for the PG10:MEH‐PPV device, the CIE coordinates at this voltage were (0.30, 0.40) with a maximum brightness of 1930 cd/m2. Moreover, the white‐light emission from the PG10:PFR4‐S device was stable even at different driving voltages and had CIE coordinates of (0.34, 0.36) at 6 V and (0.31, 0.35) at 10 V. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1199–1209, 2007  相似文献   

13.
The quantum efficiencies of photoluminescence (PL) and electro‐luminescence (EL) of poly[2‐methoxy‐5‐(2′‐ethyl‐hexyloxy)‐1,4‐phenylenevinylene] (MEH‐PPV) were significantly increased by heat treatments under vacuum with further removing the undissolved portion. The UV–vis absorption was found to decrease with heating time, while PL intensity increased. The maximum PL quantum yield was 6.5 times that of the untreated MEH‐PPV, which was attributed to the reduction of chain aggregations and the interruption of conjugation length. The maximum EL quantum yield of their prepared ITO/PANI/MEH‐PPV/Ca/AL light emitting diodes (PLED) was 46 (at 3 V) times that of the untreated sample. A typical turn‐on voltage of 2.5 V for MEH‐PPV PLED was able to decrease to 1 V after heat treatments, which was believed to result from the decrease of cis linkages in the polymer chains as revealed by the 1H NMR spectroscopy. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1705–1711, 2005  相似文献   

14.
Electrospinning is a powerful technique to produce nanofibers of tunable diameter and morphology for medicine and biotechnological applications. By doping electrospun nanofibers with inorganic and organic compounds, new functionalities can be provided for technological applications. Herein, we report a study on the morphology and optical properties of electrospun nanofibers based on the conjugated polymer poly[2‐methoxy‐5‐(2‐ethylhexyloxy)‐1,4‐phenylenevinylene] (MEH‐PPV) and poly(methylmethacrylate) (PMMA). Initially, we investigate the influence of the solvent, surfactant, and the polymer concentration on electrospinning of PMMA. After determining the best conditions, 0.1% MEH‐PPV was added to obtain fluorescent nanofibers. The optical characterizations display the successful impregnation of MEH‐PPV into the PMMA fibers without phase separation and the preservation of fluorescent property after fiber electrospinning. The obtained results show the ability of the electrospinning approach to obtain fluorescent PMMA/MEH‐PPV nanofibers with potential for optical devices applications. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1388–1394  相似文献   

15.
Organosoluble polyhedral oligomeric silsesquioxanes (POSS) blending effect on electroluminescence properties of MEH-PPV based polymer light emitting device was investigated. Excellent compatibility and surface morphology of organosoluble POSS and MEH-PPV based composite films were observed using AFM spectroscopy. The surface roughness of POSS:MEH-PPV composite film increased with increasing POSS content. Interfacial area between the light-emitting layer and cathode was favorably enhanced for cathode electron-injection. MEH-PPV blended with POSS would create a better balance between the electron and hole fluxes for POSS:MEH-PPV composite film based devices. This led to greater current efficiency of the POSS:MEH-PPV composite film based device as compared to one with a light emitting layer of MEH-PPV. Organosoluble POSS concentration effects on the PL spectra and EL performances were also studied for the POSS:MEH-PPV composite film based polymer light emitting devices.  相似文献   

16.
Abstract

This article describes the synthesis and application of poly(1,4‐phenylene‐2,6‐pyridylurea) (MCPU) as a charge transporting and rare earth metal chelating host matrix for organic light emitting diodes (OLEDs). The chelation between MCPU and Terbium (Tb3+) (the rare earth metal used in this study), is facile in nature and persists in thin films obtained by spin coating onto various substrates. Multiple polymer chelating moieties at each Tb ion site may derive from MCPU repeat units from a single polymer chain or two polymer chains, and their respective structures are proposed. The emissive properties of these films in the presence and absence of Terbium (Tb3+) were characterized by steady state UV‐VIS absorption spectroscopy and photoluminescence (PL) spectroscopy. The PL emission from Tb(MCPU) films indicate contribution from both the host MCPU and the Tb ions. The incorporation of these films in OLEDs employing different device architectures yields electroluminescence spectra, which show the characteristic emission of the Tb ions but no emission from the host polymer matrix. Although these devices are not optimized, they exhibit an order of magnitude higher external quantum efficiency as compared to that of conventional aluminum tris 8‐hydroxyquinoline (Alq3) based OLEDs, at low current densities.  相似文献   

17.
This article explores photophysical properties and aggregation behaviors of conjugated polymer, poly[2‐methoxy, 5‐(2′‐ethylhexyloxy)‐1,4‐phenylenevinylene](MEH?PPV), in various solvent–nonsolvent systems by utilizing UV/vis absorption and photoluminescence (PL) spectroscopy. The isolated chains of MEH‐PPV dispersed in solvents including dichloromethane, chloroform, and tetrahydrofuran adopt either extended or collapsed conformations depending on local polymer–solvent interactions. Aggregation of the MEH‐PPV in these solvents is induced by addition of a poor solvent, cyclohexane. The formation of aggregates is indicated by the appearance of distinct red‐shift peaks in the absorption and PL spectra. The degree of aggregation in each solvent–nonsolvent system is compared by means of absorbance and PL intensity of the aggregate bands. In early stage of the aggregation, the amount of aggregates in system is controlled by the solubility of polymer. When the polymer chains are forced to densely pack within assembled particles by increasing ratio of cyclohexane to 99 v/v %, the conformation of individual chain plays important role. We have found that the extended chains facilitate the aggregation in the assembled particles. Increasing chain length of polymer promotes the aggregation in early stage and densely packed particles. Size distribution of the assembled particles is also found to depend on the choice of solvent. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 894–904, 2010  相似文献   

18.
Aluminum and zinc complexes of 4‐substituted 8‐hydroxyquinoline were used effectively as emissive materials in light‐emitting diodes (LED). The substituents chosen in this study were p‐methoxy‐2‐styryl, p‐diethylamino‐2‐styryl, and naphthalene‐2‐vinyl groups. Their emission spectra were red‐shifted with respect to that of aluminum tris(hydroxylquinolate) (Alq3) as a result of extending their π‐conjugation. All complexes formed amorphous glasses, which exhibited high thermal and electrical stability. Typical LED devices were fabricated by mixing the dyes with polyvinylcarbazole and spin‐coated to form thin films, which were sandwiched between ITO (indium tin oxide) and a metal electrode. These devices displayed yellow‐orange emissions with quantum efficiency ca. 0.4%.  相似文献   

19.
Two PPV‐based bipolar polymers containing 1,3,4‐oxadiazole pendant groups were synthesized via the Gilch polymerization reaction for use in light‐emitting diodes (LEDs). The resulting polymers were characterized using 1H and 13C NMR, elemental analysis, DSC, and TGA. These polymers were found to be soluble in common organic solvents and are easily spin‐coated onto glass substrates, producing high optical quality thin films without defects. The electro‐optical properties of ITO/PEDOT/polymer/Al devices based on these polymers were investigated using UV‐visible, PL, and EL spectroscopy. The turn‐on voltages of the OC1Oxa‐PPV and OC10Oxa‐PPV devices were found to be 8.0 V. The maximum brightness and luminescence efficiency of the OC1Oxa‐PPV device were found to be 544 cd/m2 at 19 V and 0.15 cd/A, respectively. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1098–1110, 2008  相似文献   

20.
With the prospect of extremely fast manufacture of very low cost devices, organic electronics prepared by thin film processing techniques that are compatible with roll‐to‐roll (R2R) methods are presently receiving an increasing interest. Several technologies using organic thin films are at the point, where transfer from the laboratory to a more production‐oriented environment is within reach. In this review, we aim at giving an overview of some of the R2R‐compatible techniques that can be used in such a transfer, as well the current status of R2R application within some of the existing research fields such as organic photovoltaics, organic thin film transistors, light‐emitting diodes, polymer electrolyte membrane fuel cells, and electrochromic devices. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012  相似文献   

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