904 resultados para Poly(3-hydroxybutyrate) (PHB)


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Hybrid bulk heterojunction solar cells based on blend of poly(3-hexylthiophene) (P3HT) and TiO2 nanotubes or dye(N719) modified TiO2 nanotubes were processed from solution and characterized to research the nature of organic/inorganic hybrid materials. Compared with the pristine polymer P3HT and TiO2 nanoparticles/P3HT solar cells, the TiO2 nanotubes/P3HT hybrid solar cells show obvious performance improvement, due to the formation of the bulk heterojunction and charge transport improvement. A further improvement in the device performance can be achieved by modifying TiO2 nanotube surface with a standard dye N719 which can play a role in the improvement of both the light absorption and charge dissociation. Compared with the non-modified TiO2 nanotubes solar cells, the modified ones have better power conversion efficiency under 100 mW/cm(2) illumination with 500W Xenon lamp. (C) 2008 Elsevier B. V. All rights reserved.

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Poly(3,4-ethylenedioxythiopliene):poly(styrene sulfonate) (PEDOT:PSS) films have been electrochemically polymerized in situ on ITO glass substrate in boron trifluoride diethyl etherate electrolyte (BFEE). Cyclic voltammograms show good redox activity and stability of the PEDOT films. These films had been directly used to fabricate organic-inorganic hybrid solar cells with the structure of ITO/PEDOT/ZnO:MDMC-PPV/Al. The solar cells made of electrochemically polymerized films exhibit higher energy conversion efficiencies compared with that prepared by the spin-coating method, and the highest value is 0.33%. This in-situ electropolymerized method effectively simplifies fabricating procedures and may blaze a facile and economical route for producing high-efficiency solar cells.

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Poly (3-butylthiophene) (P3BT) is a much less studied conjugated polymer despite its high crystallizability and thus excellent electrical property. In this work, morphology of P3BT at different crystalline polymorphs and solvent/thermal induced phase transition between form I and U modifications have been intensively investigated by using optical microscopy, electron microscopy, differential scanning calorimetry, and X-ray diffraction. It is shown that a direct deposition from carbon disulfide (CS2) at fast evaporation results in P3BT crystals in form I modification, giving typical whiskerlike morphology. In contrast, low evaporation rate from CS, leads to formation of form II crystals with spherulitic morphology, which is so far scarcely observed in polythiophene.

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The substantial crystallization suppression of poly(3-hexylthiophene) (P3HT) in the untreated P3HT:C60 composite film prepared from o-dichlorobenzene (ODCB) solution has been revealed. Besides, the effective conjugation length of P3HT in this composite has been nearly maintained to that in the solution. The different crystallization behaviors of P3HT in its composites with C60 and [6,6]-phenyl C-61 butyric acid methyl ester (PCBM) are mainly attributed to the relative solubility of C60 and PCBM with respect to P3HT in ODCB. The solution to overcome this disadvantage of chain conformation and crystallinity of P3HT in the composite with C60 is thus proposed and finalized by resorting to the addition of low volatile solvent with much higher solubility of C60 than P3HT into the main solvent used, so as P3HT can crystallize before C60 forms crystallites in the solution. The feasibility of this approach has been proven by the improved efficiency of devices based on composites of P3HT and the low cost C60 without resorting to post-treatments.

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Nanoscale-phase separation of electron donor/acceptor blends is crucial for efficient charge generation and collection in Polymer bulk heterojunction photovoltaic cells. We investigated solvent vapor annealing effect of poly(3-hexylthiophene) (P3HT)/methanofullerene (PCBM) blend oil its morphology and optoelectronic properties. The organic solvents of choice for the treatment have a major effect oil the morphology of P3HT/PCBM blend and the device performance. Ultraviolet-visible absorption spectro,;copy shows that specific solvent vapor annealing can induce P3HT self-assembling to form well-ordered structure; and hence, file absorption in the red region and the hole transport are enhanced. The solvent that has a poor Solubility to PCBM Would cause large PCBM Clusters and result in a rough blend film. By combining an appropriate solvent vapor treatment and post-thermal annealing of the devices, the power conversion efficiency is enhanced.

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Herein, an insulating fluorinated polyimide (F-PI) is utilized as an ultrathin buffer layer of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) in polymer light-emitting diodes to enhance the device performance. The selective solubility of F-PI in common solvents avoids typical intermixing interfacial problems during the sequential multilayer spin-coating process. Compared to the control device, the F-PI modification causes the luminous and power efficiencies of the devices to be increased by a factor of 1.1 and 4.7, respectively, along with almost 3-fold device lifetime enhancement. Photovoltaic measurement, single-hole devices, and X-ray photoelectron spectroscopy, are utilized to investigate the underlying, mechanisms, and it is found that the hole injection barrier is lowered owing to the interactions between the PEDOT:PSS and F-PI. The F-PI modified PEDOT:PSS layer demonstrates step-up ionization potential profiles from the intrinsic bulk PEDOT:PSS side toward the F-PI-modified PEDOT:PSS surface, which facilitate the hole injection.

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Crystalline poly (3-hexylthiophene) (P3HT) nanofibrils are introduced into the P3HT: [6, 6]-phenyl C61-butyric acid methyl ester (PCBM) composite films via P3HT preaggregation in solution by adding a small amount of acetone, and the correlation of P3HT nanofibrils and the optoelectronic properties of P3HT:PCBM bulk heterojunction photovoltaic cells is investigated. It is found that the optical absorption and the hole transport or the resulted P3HT:PCBM composite films increase with the increase of the amount of P3HT nanofibrils due to the increased P3HT crystallinity and highly interconnected nanofibrillar P3HT networks. However, it is also found that high contents of crystalline P3HT nanofibrils may restrain PCBM molecules from demixing with the P3HT component that forms electron traps in the active layer. and hence reduce the charge collection efficiency. Small contents of P3HT nanofibrils not only improve the demixing between P3HT and PCBM components, but also enhance the hole transport via crystalline P3HT nanofibrillar networks, resulting in efficient charge collection.

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Needle-like single crystals of poly(3-octylthiophene) (P3OT) have been prepared by tetrahydrofuran-vapor annealing. The morphology and structure of the crystals were characterized with optical microscopy, scanning electron microscopy, atomic force microscopy, transmission electron microscopy, and wide-angle X-ray diffraction. It is observed that the P3OT molecules are packed with the backbones parallel to the length axis of the crystal and the alkyl side chains perpendicular to the substrate. The field effect transistor based on the P3OT single crystal exhibited a charge carrier mobility of 1.54 x 10(-4) cm(2)/(Vs) and on/off current ratio of 37, and the molecular orientation of the crystal is ascribed to account for the device performance. The time-dependent morphological evolution demonstrated that the crystals underwent Ostwald ripening when annealed.

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The authors report enhanced poly(3-hexylthiophene) (P3HT):methanofullerene (PCBM) bulk-heterojunction photovoltaic cells via 1,2-dichlorobenzene (DCB) vapor treatment and thermal annealing. DCB vapor treatment can induce P3HT self-organizing into ordered structure leading to enhanced absorption and high hole mobility. Further annealing the device at a high temperature, PCBM molecules begin to diffuse into aggregates and together with the ordered P3HT phase form bicontinuous pathways in the entire layer for efficient charge separation and transport. Compared to the control device that is merely annealed, optical absorption, short-circuit current, and power conversion efficiency are increased for the DCB vapor-treated cell.

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Single crystals of head-to-tail poly(3-hexylthiophene)s have been grown through the method of isothermal solution crystallization. Electron diffraction in combination with powder X-ray diffraction revealed the crystal structure, a = 1.52 nm, b = 3.36 nm, c = 1.56 nm and alpha = beta = gamma = 90 degrees.

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We developed an approach, i.e. solvent-assist crystallization (SAC), for growing high quality single crystals of head-to-tail regio-regular poly(3-butylthiophene) (P3BT). By means of atomic force microscopy, electron diffraction and X-ray diffraction, we found that P3BT macromolecules formed lamella single crystals through gradient crystallization, and in the single crystals, molecules packed normal to the lamella with extended-chain conformation with alkyl side chains in the growth front during crystallization.

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Poly(4-styrene sulfonate)-doped poly(3,4-ethylenedioxythiophene) (PEDOT/PSS) films with ring-, arrow-, and bubble-like microstructures have been electrochemically generated simply by a one-step cyclic voltammetry in an aqueous media. Influences of applied potentials and surfactant/dopant-PSS on morphology of the resulting film were investigated, and a gas bubble template mechanism has been proposed. The result confirmed a well-doping of PSS in the PEDOT film. Electrochemical property and conductivity of the micro-structured PEDOT/PSS film were investigated further. Similar preparation with potential applications in fabrication of microdevices and micro-sensors can be extended to other micro-structured conducting polymers.

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The electrolyte, NaBF4, can be enriched into the matrix of poly(3,4-ethylenedioxythiophene) (PEDOT) film during the p-doping potential cycling between 0.6 and -0.9 V. It has been demonstrated that this enrichment is originated from the mixed ion transfer between doping and dedoping, i.e. BF4- anion migrate into the PEDOT film during the oxidation process, the Ne cation insert into the film during the reduction process, and then, the electrolyte is accumulated into the film matrix after the multiple CV cycling. The quantitative analysis of energy-dispersive X-ray spectroscopy (EDX) confirmed the enrichment of NaBF4 in the PEDOT film.

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Maleic anhydride end capped poly(propylene carbonate) (PPC-MA) was blended with ethyl cellulose (EC) by casting from dichloromethane solutions. The thermotropic liquid crystallinity, thermal decomposition behavior, and aggregated structure were investigated by differential scanning calorimetry (DSC), thermogravimetry (TGA), and wide angle X-ray diffraction (WAXD). DSC exhibits thermotropic liquid crystallinity in the rich EC composition range. TGA shows that thermal decomposition temperatures were elevated upon interfusing EC into PPC-MA. WAXD corroborates that EC and PPC-MA/EC blend films cast from dilute dichloromethane solution possessed cholesteric liquid crystalline structure in the rich EC composition range, and that dilution of PPC-MA with EC increased the dimension of noncrystalline region, leading to a more ordered packed structure.