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Regioregular Poly (regioregular + poly)
Selected AbstractsIntramolecular Donor,Acceptor Regioregular Poly(hexylphenanthrenyl-imidazole thiophene) Exhibits Enhanced Hole Mobility for Heterojunction Solar Cell ApplicationsADVANCED MATERIALS, Issue 20 2009Yao-Te Chang PHPIT, a new kind of intramolecular donor,acceptor side-chain-tethered hexylphenanthrenyl-imidazole polythiophene is synthesized. The more-balanced electron and hole mobilities and the enhanced visible- and internal-light absorptions in the devices consisting of annealed PHPIT/PCBM blends both contribute to a much higher short-circuit current density, which in turn led to a power conversion efficiency as high as 4.1%. [source] Polymer Charge Transport: Charge-Transport Anisotropy Due to Grain Boundaries in Directionally Crystallized Thin Films of Regioregular Poly(3-hexylthiophene) (Adv. Mater.ADVANCED MATERIALS, Issue 16 200916/2009) Grain boundaries can be engineered in directionally oriented thin films of poly(3-hexylthiophene) report Alberto Salleo and co-workers on p. 1568. Charge-transport studies coupled with X-ray and AFM characterization indicate that intergrain transport is greatly facilitated when neighboring grains can be bridged by relatively straight polymer chains. [source] Charge-Transport Anisotropy Due to Grain Boundaries in Directionally Crystallized Thin Films of Regioregular Poly(3-hexylthiophene)ADVANCED MATERIALS, Issue 16 2009Leslie H. Jimison P3HT films that are highly anisotropic in-plane are produced using a directional crystallization technique, and the charge-transport properties of grain bourdaries between different orientations of crystallites are studied. Boundaries along the fiber provide a small barrier to charge transport when compared to fiber-to-fiber grain boundaries. The films allow a correlation to be drawn between the grain-boundary type and charge-transport behavior in P3HT. [source] Synthesis and Characterization of Nanocomposites Based on Functional Regioregular Poly(3-hexylthiophene) and Multiwall Carbon NanotubesMACROMOLECULAR RAPID COMMUNICATIONS, Issue 16 2010Florian Boon Abstract New functionalized poly(3-hexylthiophene)s (P3HT) have been designed and synthesized with the aim of increasing the dispersion of carbon nanotubes (CNT) in solutions and in thin films of semiconducting polymers. Dispersion in solution has been assessed by sedimentation tests while the thin film morphology has been analyzed by TEM and AFM. Both the physisorption of P3HT chains (via pyrene end-groups) or their chemical grafting (onto amine functions generated on the CNT surface) lead to a much better dispersion in solution and in the solid. In thin films, P3HT fibrils are observed to arrange perpendicular to the CNT surface, which can be understood on the basis of molecular modeling simulations. Finally, the effect of dispersing those P3HT/CNT nanocomposites in bulk-heterojunction P3HT-based photovoltaic devices has been evaluated. [source] Regioregular Poly[3-(4-alkoxyphenyl)thiophene]s: Evidence for a Two-Step Aggregation ProcessMACROMOLECULAR RAPID COMMUNICATIONS, Issue 14 2006Guy Koeckelberghs Abstract Summary: A chiral, regioregular poly[3-(4-alkoxyphenyl)thiophene] has been prepared and studied. Films prepared by fast evaporation of the solvent, consist of random-coils, while films prepared by slow evaporation are composed of chirally aggregated, coplanar strands. Heat treatment transforms the random-coils into aggregated films via an intermediate state, which was characterized as chiral, coplanar, unaggregated polymer strands. Overview of the possible aggregation processes. [source] Characteristics of Photoexcitations and Interfacial Energy Levels of Regioregular Poly(3-hexythiophene-2,5-diyl) on Gold,CHEMPHYSCHEM, Issue 13 2007Youngku Sohn Dr. Abstract We have studied characteristics of photoexcitations and interfacial electronic structures of regioregular poly(3-hexlythiophene-2,5-diyl) (P3HT) on gold using two-photon photoemission (2PPE) spectroscopy. The vacuum level threshold is decreased by 1.3 eV from that of bare gold, attributable to interface dipole effects. The 2PPE spectral width narrows as the film thickness increases. We tentatively understand that this is due to destabilization of long-lived localized polaron, attributed to strong interchain interactions. On the basis of the analysis of the 2PPE distribution as a function of photon energy and laser power, the polaron level is located at 3.1 eV below the vacuum level. Using this value and a polaron level of 1.75 eV above the HOMO, we indirectly estimate an ionization potential of 4.85 eV for P3HT. An increase in two-photon photoemission yield with increasing photon energy is attributed to an enhanced electron-hole pair dissociation yield at higher photo-excitation levels. The decrease in power law slope with increasing film thickness is understood by Langevin recombination kinetics and saturation of photoexcitations [source] Photo-induced Charge Transfer and Relaxation of Persistent Charge Carriers in Polymer/Nanocrystal Composites for Applications in Hybrid Solar CellsADVANCED FUNCTIONAL MATERIALS, Issue 23 2009Marc Daniel Heinemann Abstract The photo-induced charge transfer and the dynamics of persistent charge carriers in blends of semiconducting polymers and nanocrystals are investigated. Regioregular poly(3-hexylthiophene) (P3HT) is used as the electron donor material, while the acceptor moiety is established by CdSe nanocrystals (nc-CdSe) prepared via colloidal synthesis. As a reference system, organic blends of P3HT and [6,6]-phenyl C61 -butyric acid methyl ester (PCBM) are studied as well. The light-induced charge transfer between P3HT and the acceptor materials is studied by photoluminescence (PL), photo-induced absorption (PIA) and light-induced electron spin resonance spectroscopy (LESR). Compared to neat P3HT samples, both systems show an intensified formation of polarons in the polymer upon photo-excitation, pointing out successful separation of photogenerated charge carriers. Additionally, relaxation of the persistent charge carriers is investigated, and significant differences are found between the hybrid composite and the purely organic system. While relaxation, reflected in the transient signal decay of the polaron signal, is fast in the organic system, the hybrid blends exhibit long-term persistence. The appearance of a second, slow recombination channel indicates the existence of deep trap states in the hybrid system, which leads to the capture of a large fraction of charge carriers. A change of polymer conformation due to the presence of nc-CdSe is revealed by low temperature LESR measurements and microwave saturation techniques. The impact of the different recombination behavior on the photovoltaic efficiency of both systems is discussed. [source] Regioregular poly(3-alkanoylthiophene): Synthesis and electrochemical, photophysical, charge transport, and photovoltaic propertiesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2010Chao Wang Abstract Head-to-tail regioregular poly(3-heptanoylthiophene) (PHOT) was synthesized by Ni-catalyzed polycondensation of the 2,2-dimethyl-1,3-propanediol-protected Grignard monomer followed by deprotection. Cyclic voltammetric (CV) study demonstrates that the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of PHOT are 0.5 eV lower in energy than those of the head-to-tail poly(3-hexylthiophene) (HT-P3HT). Their optical band gaps are essentially the same. Incomplete photoluminescence (PL) quenching was observed in thin films of the 1:1 blend of PHOT and HT-P3HT. PHOT displayed a glass transition at ,269 °C and decomposed at ,300 °C according to differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Wide-angle X-ray diffraction (WAXD) study showed that PHOT exists in a not highly ordered state in solid films especially in the ,-stacking direction. Only p -channel activity was observed in field-effect transistors (FETs) for PHOT. The hole mobility was on the order of 10,4 cm2 V,1 s,1. Photovoltaic devices with an active layer of 1:1 blend of PHOT and PC71BM had a power conversion efficiency (PCE) of ,0.5%. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 [source] Synthesis, Morphology, and Properties of Poly(3-hexylthiophene)- block -Poly(vinylphenyl oxadiazole) Donor,Acceptor Rod,Coil Block Copolymers and Their Memory Device ApplicationsADVANCED FUNCTIONAL MATERIALS, Issue 18 2010Yi-Kai Fang Abstract Novel donor,acceptor rod,coil diblock copolymers of regioregular poly(3-hexylthiophene) (P3HT)- block -poly(2-phenyl-5-(4-vinylphenyl)-1,3,4-oxadiaz-ole) (POXD) are successfully synthesized by the combination of a modified Grignard metathesis reaction (GRIM) and atom transfer radical polymerization (ATRP). The effects of the block ratios of the P3HT donor and POXD pendant acceptor blocks on the morphology, field effect transistor mobility, and memory device characteristics are explored. The TEM, SAXS, WAXS, and AFM results suggest that the coil block fraction significantly affects the chain packing of the P3HT block and depresses its crystallinity. The optical absorption spectra indicate that the intramolecular charge transfer between the main chain P3HT donor and the side chain POXD acceptor is relatively weak and the level of order of P3HT chains is reduced by the incorporation of the POXD acceptor. The field effect transistor (FET) hole mobility of the system exhibits a similar trend on the optical properties, which are also decreased with the reduced ordered P3HT crystallinity. The low-lying highest occupied molecular orbital (HOMO) energy level (,6.08 eV) of POXD is employed as charge trap for the electrical switching memory devices. P3HT- b -POXD exhibits a non-volatile bistable memory or insulator behavior depending on the P3HT/POXD block ratio and the resulting morphology. The ITO/P3HT44 - b - POXD18/Al memory device shows a non-volatile switching characteristic with negative differential resistance (NDR) effect due to the charge trapped POXD block. These experimental results provide the new strategies for the design of donor-acceptor rod-coil block copolymers for controlling morphology and physical properties as well as advanced memory device applications. [source] Planarization of Polymeric Field-Effect Transistors: Improvement of Nanomorphology and Enhancement of Electrical PerformanceADVANCED FUNCTIONAL MATERIALS, Issue 14 2010Kumar A. Singh Abstract The planarization of bottom-contact organic field-effect transistors (OFETs) resulting in dramatic improvement in the nanomorphology and an associated enhancement in charge injection and transport is reported. Planar OFETs based on regioregular poly(3-hexylthiophene) (rr-P3HT) are fabricated wherein the Au bottom-contacts are recessed completely in the gate-dielectric. Normal OFETs having a conventional bottom-contact configuration with 50-nm-high contacts are used for comparison purpose. A modified solvent-assisted drop-casting process is utilized to form extremely thin rr-P3HT films. This process is critical for direct visualization of the effect of planarization on the polymer morphology. Atomic force micrographs (AFM) show that in a normal OFET the step between the surface of the contacts and the gate dielectric disrupts the self-assembly of the rr-P3HT film, resulting in poor morphology at the contact edges. The planarization of contacts results in notable improvement of the nanomorphology of rr-P3HT, resulting in lower resistance to charge injection. However, an improvement in field-effect mobility is observed only at short channel lengths. AFM shows the presence of well-ordered nanofibrils extending over short channel lengths. At longer channel lengths the presence of grain boundaries significantly minimizes the effect of improvement in contact geometry as the charge transport becomes channel-limited. [source] Spin- and Spray-Deposited Single-Walled Carbon-Nanotube Electrodes for Organic Solar CellsADVANCED FUNCTIONAL MATERIALS, Issue 14 2010Sungsoo Kim Abstract Organic bulk-heterojunction solar cells using thin-film single-walled carbon-nanotube (SWCNT) anodes deposited on glass are reported. Two types of SWCNT films are investigated: spin-coated films from dichloroethane (DCE), and spray-coated films from deionized water using sodium dodecyl sulphate (SDS) or sodium dodecyl benzene sulphonate (SDBS) as the surfactant. All of the films are found to be mechanically robust, with no tendency to delaminate from the underlying substrate during handling. Acid treatment with HNO3 yields high conductivities >1000,S,cm,1 for all of the films, with values of up to 7694,±,800,S,cm,1 being obtained when using SDS as the surfactant. Sheet resistances of around 100,,,sq,1 are obtained at reasonable transmission, for example, 128,±,2,,,sq,1 at 90% for DCE, 57,±,3,,,sq,1 at 65% for H2O:SDS, and 68,±,5,,,sq,1 at 70% for H2O:SDBS. Solar cells are fabricated by successively coating the SWCNT films with poly(3,4-ethylenedioxythiophene):poly(styrene sulphonate) (PEDOT:PSS), a blend of regioregular poly(3-hexylthiophene) (P3HT) and 1-(3-methoxy-carbonyl)-propyl-1-phenyl-(6,6)C61 (PCBM), and LiF/Al. The resultant devices have respective power conversions of 2.3, 2.2 and 1.2% for DCE, H2O:SDS and H2O:SDBS, with the first two being at a virtual parity with reference devices using ITO-coated glass as the anode (2.3%). [source] Lateral Inhomogeneity in the Electronic Structure of a Conjugated Poly(3-hexylthiophene) Thin FilmADVANCED FUNCTIONAL MATERIALS, Issue 13 2010Kaname Kanai Abstract How annealing influences the morphology of a highly regioregular poly(3-hexylthiophene) (RR-P3HT) film at the substrate interface as well as the lateral inhomogeneity in the electronic structure of the film are elucidated. Whereas previous studies have reported that high-molecular-weight (MW) RR-P3HT films tend to show low crystallinity even after annealing, it is found that high-MW RR-P3HT does show high crystallinity after annealing at high temperature for a long time. Photoemission electron microscopy (PEEM), X-ray photoemission spectroscopy, and ultraviolet photoemission spectroscopy results clearly resolve a considerable lateral inhomogeneity in the morphology of RR-P3HT film, which results in a variation of the electronic structure depending on the local crystallinity. The PEEM results show how annealing facilitates crystal growth in a high-MW RR-P3HT film. [source] Abrupt Morphology Change upon Thermal Annealing in Poly(3-Hexylthiophene)/Soluble Fullerene Blend Films for Polymer Solar CellsADVANCED FUNCTIONAL MATERIALS, Issue 5 2010Minjung Shin Abstract The in situ morphology change upon thermal annealing in bulk heterojunction blend films of regioregular poly(3-hexylthiophene) (P3HT) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61 (PCBM) is measured by a grazing incidence X-ray diffraction (GIXD) method using a synchrotron radiation source. The results show that the film morphology,including the size and population of P3HT crystallites,abruptly changes at 140,°C between 5 and 30,min and is then stable up to 120,min. This trend is almost in good agreement with the performance change of polymer solar cells fabricated under the same conditions. The certain morphology change after 5,min annealing at 140,°C is assigned to the on-going thermal transition of P3HT molecules in the presence of PCBM transition. Field-emission scanning electron microscopy measurements show that the crack-like surface of blend films becomes smaller after a very short annealing time, but does not change further with increasing annealing time. These findings indicate that the stability of P3HT:PCBM solar cells cannot be secured by short-time annealing owing to the unsettled morphology, even though the resulting efficiency is high. [source] Aligned Nanofibers: Epitaxial Growth of Highly Oriented Fibers of Semiconducting Polymers with a Shish-Kebab-Like Superstructure (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 17 2009Mater. Highly oriented fibers of regioregular poly(3-alkylthiophene)s with a "shish-kebab" morphology are prepared by epitaxy on long needles of 1,3,5-trichlorobenzene grown in liquid pyridine, as described on page 2759 by Brinkmann et al. The superstructure of the fibers consists of a highly oriented thread-like core several hundreds of micrometers long, the "shish", onto which lateral crystalline nanofibrils made of folded polymer chains, the "kebabs", are connected in a periodic way. [source] Epitaxial Growth of Highly Oriented Fibers of Semiconducting Polymers with a Shish-Kebab-Like SuperstructureADVANCED FUNCTIONAL MATERIALS, Issue 17 2009Martin Brinkmann Abstract Highly oriented fibers of regioregular poly(3-alkylthiophene)s (P3ATs) showing a "shish-kebab" morphology are prepared by oriented epitaxial crystallization in a mixture of 1,3,5-trichlorobenzene (TCB) and pyridine. The superstructure of the P3AT fibers consists of an oriented thread-like core several hundreds of micrometers long, the "shish", onto which lateral crystalline fibrils made of folded polymer chains, the "kebabs", are connected in a periodic way with a periodicity in the range 18,30,nm. The P3AT-chain axis is oriented parallel to the fiber axis whereas the ,-stacking direction is oriented perpendicular to it. The oriented character of the shish-kebab fibers results in polarized optical absorption and photoluminescence. The formation of oriented precursors by epitaxial orientation of polymer chains onto long needles of a molecular crystal,TCB in the present case,appears to be an original alternative to the crystallization usually performed under external flow conditions. [source] Three-Dimensional Bulk Heterojunction Morphology for Achieving High Internal Quantum Efficiency in Polymer Solar CellsADVANCED FUNCTIONAL MATERIALS, Issue 15 2009Jang Jo Abstract Here, an investigation of three-dimensional (3D) morphologies for bulk heterojunction (BHJ) films based on regioregular poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61 -butyric acid methyl ester (PCBM) is reported. Based on the results, it is demonstrated that optimized post-treatment, such as solvent annealing, forces the PCBM molecules to migrate or diffuse toward the top surface of the BHJ composite films, which induces a new vertical component distribution favorable for enhancing the internal quantum efficiency (,IQE) of the devices. To investigate the 3D BHJ morphology, novel time-of-flight secondary-ion mass spectroscopy studies are employed along with conventional methods, such as UV-vis absorption, X-ray diffraction, and high-resolution transmission electron microscopy studies. The ,IQE of the devices are also compared after solvent annealing for different times, which clearly shows the effect of the vertical component distribution on the performance of BHJ polymer solar cells. In addition, the fabrication of high-performance P3HT:PCBM solar cells using the optimized solvent-annealing method is reported, and these cells show a mean power-conversion efficiency of 4.12% under AM 1.5G illumination conditions at an intensity of 100,mW cm,2. [source] Solubility-Induced Ordered Polythiophene Precursors for High-Performance Organic Thin-Film TransistorsADVANCED FUNCTIONAL MATERIALS, Issue 8 2009Yeong Don Park Abstract With the aim of enhancing the field-effect mobility of self-assembled regioregular poly(3-hexylthiophene), P3HT, by promoting two-dimensional molecular ordering, the organization of the P3HT in precursor solutions is transformed from random-coil conformation to ordered aggregates by adding small amounts of the non-solvent acetonitrile to the solutions prior to film formation. The ordering of the precursor in the solutions significantly increases the crystallinity of the P3HT thin films. It is found that with the appropriate acetonitrile concentration in the precursor solution, the resulting P3HT nanocrystals adopt a highly ordered molecular structure with a field-effect mobility dramatically improved by a factor of approximately 20 depending on the P3HT concentration. This improvement is due to the change in the P3HT organization in the precursor solution from random-coil conformation to an ordered aggregate structure as a result of the addition of acetonitrile. In the good solvent chloroform, the P3HT molecules are molecularly dissolved and adopt a random-coil conformation, whereas upon the addition of acetonitrile, which is a non-solvent for aromatic backbones and alkyl side chains, 1D or 2D aggregation of the P3HT molecules occurs depending on the P3HT concentration. This state minimizes the unfavorable interactions between the poorly soluble P3HT and the acetonitrile solvent, and maximizes the favorable ,,, stacking interactions in the precursor solution, which improves the molecular ordering of the resulting P3HT thin film and enhances the field-effect mobility without post-treatment. [source] Hybrid Solar Cells from Regioregular Polythiophene and ZnO Nanoparticles,ADVANCED FUNCTIONAL MATERIALS, Issue 8 2006Abstract Blends of nanocrystalline zinc oxide nanoparticles (nc-ZnO) and regioregular poly(3-hexylthiophene) (P3HT) processed from solution have been used to construct hybrid polymer,metal oxide bulk-heterojunction solar cells. Thermal annealing of the spin-cast films significantly improves the solar-energy conversion efficiency of these hybrid solar cells to ,,0.9,%. Photoluminescence and photoinduced absorption spectroscopy demonstrate that charge-carrier generation is not quantitative, because a fraction of P3HT appears not to be in contact with or in close proximity to ZnO. The coarse morphology of the films, also identified by tapping-mode atomic force microscopy, likely limits the device performance. [source] Direct Spectroscopic Evidence for a Photodoping Mechanism in Polythiophene and Poly(bithiophene- alt -thienothiophene) Organic Semiconductor Thin Films Involving Oxygen and Sorbed MoistureADVANCED MATERIALS, Issue 46 2009Jing-Mei Zhuo Direct infrared spectroscopic evidence has been obtained for photodoping of high mobility regioregular poly(3-alkylthiophene) and poly[2,5-bis(3-alkyllthiophen-2-yl) thieno (3,2-b)thiophene] with the attendant formation of hydroxide counter-ions. This reveals the central role of dissolved water, explains the key features of degradation of the electrical characteristics of organic semiconductors in the ambient (see figure), and points to possible strategies to further improve their stability. [source] Regioregular poly(3-alkanoylthiophene): Synthesis and electrochemical, photophysical, charge transport, and photovoltaic propertiesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2010Chao Wang Abstract Head-to-tail regioregular poly(3-heptanoylthiophene) (PHOT) was synthesized by Ni-catalyzed polycondensation of the 2,2-dimethyl-1,3-propanediol-protected Grignard monomer followed by deprotection. Cyclic voltammetric (CV) study demonstrates that the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of PHOT are 0.5 eV lower in energy than those of the head-to-tail poly(3-hexylthiophene) (HT-P3HT). Their optical band gaps are essentially the same. Incomplete photoluminescence (PL) quenching was observed in thin films of the 1:1 blend of PHOT and HT-P3HT. PHOT displayed a glass transition at ,269 °C and decomposed at ,300 °C according to differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Wide-angle X-ray diffraction (WAXD) study showed that PHOT exists in a not highly ordered state in solid films especially in the ,-stacking direction. Only p -channel activity was observed in field-effect transistors (FETs) for PHOT. The hole mobility was on the order of 10,4 cm2 V,1 s,1. Photovoltaic devices with an active layer of 1:1 blend of PHOT and PC71BM had a power conversion efficiency (PCE) of ,0.5%. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 [source] Facile syntheses, morphologies, and optical absorptions of P3HT coil-rod-coil triblock copolymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 15 2010Herman Lim Abstract Here we report syntheses, photophysical properties, and morphologies of a series of coil-rod-coil ABA triblock copolymers containing highly regioregular poly(3-hexylthiophene) (P3HT) as the central rod block. A new methodology, based on the coupling reaction between living polymeric anions [polystyrene, polyisoprene, and poly(methyl methacrylate)] and aldehyde terminated P3HT, was successfully developed to synthesize the triblock copolymers with low polydispersities. This coupling reaction was effective for building blocks with a variety of molecular weights; therefore, a good variation in compositions of the triblock copolymers could be feasibly achieved. The non-P3HT coil segments and the solvents were found to exhibit noticeable effects on morphologies of the spin-coated thin films. Attachment of the coil segments to P3HT did not change the optical absorption of the P3HT segment as the block copolymers were dissolved in solution regardless the chemical structure and the molecular weight of the coil segment. Interestingly, different UV,vis absorption behaviors were observed for the spin-coated thin films of the block copolymers, which closely related to their morphologies. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3311,3322, 2010 [source] Synthesis of soluble poly(para -phenylene) with a long polymer chain: Characteristics of regioregular poly(1,4-phenylene)JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 15 2008Itaru Natori Abstract Soluble poly(para -phenylene) having a long polymer chain (more than six repeat units) was synthesized with a tert -butyl end-group (t -PPP) and was found to have improved solubility and excellent optical properties. Poly(1,3-cyclohexadiene) (PCHD) consisting of only 1,4-cyclohexadiene (1,4-CHD) units was synthesized with a tert -butyl end-group (t -PCHD), and completely dehydrogenated to obtain t -PPP. This end-group effectively prevented the crystallization of t -PPP, and polymers containing up to 16 repeat units were soluble in tetrahydrofuran. Soluble t -PPP obtained had an ability to form a tough thin film prepared by spin-coating method. Optical analyses of t -PPP provided strong evidence for a linear polymer chain structure. A block copolymer of t -PPP and a soluble polyphenylene (PPH) was then synthesized, and the excellent optical properties were retained by this block copolymer along with its solubility. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5223,5231, 2008 [source] Regioregular Poly[3-(4-alkoxyphenyl)thiophene]s: Evidence for a Two-Step Aggregation ProcessMACROMOLECULAR RAPID COMMUNICATIONS, Issue 14 2006Guy Koeckelberghs Abstract Summary: A chiral, regioregular poly[3-(4-alkoxyphenyl)thiophene] has been prepared and studied. Films prepared by fast evaporation of the solvent, consist of random-coils, while films prepared by slow evaporation are composed of chirally aggregated, coplanar strands. Heat treatment transforms the random-coils into aggregated films via an intermediate state, which was characterized as chiral, coplanar, unaggregated polymer strands. Overview of the possible aggregation processes. [source] All-organic optocouplers based on polymer light-emitting diodes and photodetectorsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 11 2008N. A. Stathopoulos Abstract In this work, we demonstrate all organic flexible polymeric optocouplers by utilizing a donor-acceptor bulk heterojunction polymer photodetector (PD) as the output unit and a polymer light-emitting diode (PLED) as the input unit. The input unit is a single-layer PLED on a glass or a plastic (PET) substrate utilizing a green emitting polyfluorene-benzothiadiazole copolymer in the active layer. The output unit is a single-layer PD on a glass substrate utilizing a P3HT:PCBM(1:1 by weight) blend, where P3HT is regioregular poly(3-hexylthiophene) and PCBM is (6,6)-phenyl-C61 -butyric acid methyl ester. The electroluminescence spectrum of the PLED peaks at 530 nm and covers a spectral range that coincides quite well with the PD absorption spectrum (between 450 and 650 nm). The current density transfer ratio reaches 0.012% for an optocoupler that operates at 0 V and 15 V for the PD and PLED, respectively. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Ultrafast coherent vibronic oscillations in regioregular poly(3-alkylthiophene)PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S1 2009Katsuichi Kanemoto Abstract Ultrafast degenerate four-wave mixing (DFWM) signals of the regioregular (RR) poly(3-hexylthiophene) (P3HT) film have been investigated by the experiments using sub-20 fs pulses generated from a noncollinear optical parametric amplifier (NOPA) system. Strong DFWM signals were observed owing to a large third-order nonlinear susceptibility ,(3) of the RR-P3HT film. The time profile of the DFWM signals exhibits clear coherent oscillation on a decaying signal. The oscillation turn out to be caused by the C=C stretching mode that gives strong Raman signal. The time profile of the DFWM signal is simulated by a numerical calculation. The result of simulation reveals that decay constants of electronic population and of vibronic oscillation are 200 fs and 210 fs, respectively. This is the first determination of the decay constants for the RR-P3HT film. The obtained result demonstrates that the ,(3) signal of the RR-P3HT film decays very rapidly. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] A review of charge transport and recombination in polymer/fullerene organic solar cellsPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 8 2007A. Pivrikas Abstract The charge carrier transport and recombination in two types of thermally treated bulk-heterojunction solar cells is reviewed: in regioregular poly(3-hexylthiophene) (RRP3HT) mixed with 1-(3-methoxycarbonyl)propyl-1-phenyl-[6,6]-methanofullerene (PCBM) and in the blend of poly[2-methoxy-5-(3,7-dimethyloctyloxy)-phenylene vinylene] (MDMO-PPV) mixed with PCBM. The charge carrier mobility and bimolecular recombination coefficient have been comparatively studied by using various techniques including Time-of-Flight (ToF), Charge Extraction by Linearly Increasing Voltage (CELIV), Double Injection (DI) transients, Current,Voltage (I,V) technique. It was found that the carrier mobility is at least an order of magnitude higher in RRP3HT/PCBM blends compared to MDMO-PPV/PCBM. Moreover, all used techniques demonstrate a heavily reduced charge carrier recombination in RRP3HT/PCBM films compared to Langevin-type carrier bimolecular recombination in MDMO-PPV/PCBM blends. As a result of long carrier lifetimes the formation of high carrier concentration plasma in RRP3HT/PCBM blends is demonstrated and plasma extraction methods were used to directly estimate the charge carrier mobility and bimolecular recombination coefficients simultaneously. A weak dependence of bimolecular recombination coefficient on the applied electric field and temperature demonstrates that carrier recombination is not dominated by charge carrier mobility (Langevin-type recombination) in RRP3HT/PCBM blends. Furthermore, we found from CELIV techniques that electron mobility in RRP3HT/PCBM blends is independent on relaxation time in the experimental time window (approx. hundreds of microseconds to tens of milliseconds). This reduced carrier bimolecular recombination in RRP3HT/PCBM blends implies that the much longer carrier lifetimes can be reached at the same concentrations which finally results in higher photocurrent and larger power conversion efficiency of RRP3HT/PCBM solar cells. Copyright © 2007 John Wiley & Sons, Ltd. [source] Characteristics of Photoexcitations and Interfacial Energy Levels of Regioregular Poly(3-hexythiophene-2,5-diyl) on Gold,CHEMPHYSCHEM, Issue 13 2007Youngku Sohn Dr. Abstract We have studied characteristics of photoexcitations and interfacial electronic structures of regioregular poly(3-hexlythiophene-2,5-diyl) (P3HT) on gold using two-photon photoemission (2PPE) spectroscopy. The vacuum level threshold is decreased by 1.3 eV from that of bare gold, attributable to interface dipole effects. The 2PPE spectral width narrows as the film thickness increases. We tentatively understand that this is due to destabilization of long-lived localized polaron, attributed to strong interchain interactions. On the basis of the analysis of the 2PPE distribution as a function of photon energy and laser power, the polaron level is located at 3.1 eV below the vacuum level. Using this value and a polaron level of 1.75 eV above the HOMO, we indirectly estimate an ionization potential of 4.85 eV for P3HT. An increase in two-photon photoemission yield with increasing photon energy is attributed to an enhanced electron-hole pair dissociation yield at higher photo-excitation levels. The decrease in power law slope with increasing film thickness is understood by Langevin recombination kinetics and saturation of photoexcitations [source] | |||||||||||||||||||||||||