Dissertations / Theses on the topic 'Conjugated organic polymers'
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Samuel, Ifor David William. "Femtosecond spectroscopy of conjugated polymers." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239657.
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Bakbak, Selma. "Structural manipulation of conjugated polymers." Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-01112006-211158/.
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Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2006.Dr. Uwe H. F. Bunz, Committee Chair ; Dr. Laren M. Tolbert, Committee Member ; Dr. Joseph Perry, Committee Member ; Dr. David M. Collard, Committee Member ; Dr. Anselm C. Griffin, Committee Member.
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Wang, Chao. "Synthesis of Conjugated Polymers." University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1362783501.
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Isaksson, Joakim. "Organic Bioelectronics : Electrochemical Devices using Conjugated Polymers." Doctoral thesis, Linköpings universitet, Institutionen för teknik och naturvetenskap, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-9679.
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Since the Nobel Prize awarded discovery that some polymers or “plastics” can be made electronically conducting, the scientific field of organic electronics has arisen. The use of conducting polymers in electronic devices is appealing, because the materials can be processed from a liquid phase, much like ordinary non-conducting plastics. This gives the opportunity to utilize printing technologies and manufacture electronics roll-to-roll on flexible substrates, ultimately at very low costs. Even more intriguing are the possibilities to achieve completely novel functionalities in combination with the inherent compatibility of these materials with biological species. Therefore, organic electronics can be merged with biology and medicine to create organic bioelectronics, i.e. organic electronic devices that interact with biological samples directly or are used for biological applications. This thesis aims at giving a background to the field of organic bioelectronics and focuses on how electrochemical devices may be utilized. An organic electronic wettability switch that can be used for lab-on-a-chip applications and control of cell growth as well as an electrochemical ion pump for cell communication and drug delivery are introduced. Furthermore, the underlying electrochemical structures that are the basis for the above mentioned devices, electrochemical display pixels etc. are discussed in detail. In summary, the work contributes to the understanding of electrochemical polymer electronics and, by presenting new bioelectronic inventions, builds a foundation for future projects and discoveries.
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Vokata, Tereza. "Synthetic Approaches to Flexible Fluorescent Conjugated Polymers." FIU Digital Commons, 2015. http://digitalcommons.fiu.edu/etd/1910.
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Conjugated polymers (CPs) are intrinsically fluorescent materials that have been used for various biological applications including imaging, sensing, and delivery of biologically active substances. The synthetic control over flexibility and biodegradability of these materials aids the understanding of the structure-function relationships among the photophysical properties, the self-assembly behaviors of the corresponding conjugated polymer nanoparticles (CPNs), and the cellular behaviors of CPNs, such as toxicity, cellular uptake mechanisms, and sub-cellular localization patterns.
Synthetic approaches towards two classes of flexible CPs with well-preserved fluorescent properties are described. The synthesis of flexible poly(p-phenylenebutadiynylene)s (PPBs) uses competing Sonogashira and Glaser coupling reactions and the differences in monomer reactivity to incorporate a small amount (~10%) of flexible, non-conjugated linkers into the backbone. The reaction conditions provide limited control over the proportion of flexible monomer incorporation. Improved synthetic control was achieved in a series of flexible poly(p-phenyleneethynylene)s (PPEs) using modified Sonogashira conditions. In addition to controlling the degree of flexibility, the linker provides disruption of backbone conjugation that offers control of the length of conjugated segments within the polymer chain. Therefore, such control also results in the modulation of the photophysical properties of the materials.
CPNs fabricated from flexible PPBs are non-toxic to cells, and exhibit subcellular localization patterns clearly different from those observed with non-flexible PPE CPNs. The subcellular localization patterns of the flexible PPEs have not yet been determined, due to the toxicity of the materials, most likely related to the side-chain structure used in this series.
The study of the effect of CP flexibility on self-assembly reorganization upon polyanion complexation is presented. Owing to its high rigidity and hydrophobicity, the PPB backbone undergoes reorganization more readily than PPE. The effects are enhanced in the presence of the flexible linker, which enables more efficient π-π stacking of the aromatic backbone segments. Flexibility has minimal effects on the self-assembly of PPEs. Understanding the role of flexibility on the biophysical behaviors of CPNs is key to the successful development of novel efficient fluorescent therapeutic delivery vehicles.
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Isaksson, Joakim. "Organic bioelectronics : electrochemical devices based on conjugated polymers /." Norrköping : [Department of Science and Technology], Linköping University, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-9679.
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Chen, Yi 1974. "Organic thin film transistors based on conjugated polymers." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=81533.
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Thin film transistors with different polymers (PTFTs) as active channel layers have been fabricated and studied in this work. Three different fabrication procedures were used to fabricate long and short channel PTFTs on silicon substrates and long channel PTFTs on glass substrates. It has been shown that the success rate of fabrication of PTFTs on glass substrates with anodic Al 2O3 gate dielectrics is higher than that on silicon substrates with thermally grown SiO2 gate dielectrics.The characteristics of PTFTs fabricated using several polymers were studied. Among them, the ones based on regioregualr poly[3-hexylthiophene-2.5diy] (RR-P3HT) have the best performance with a field effect mobility (mueff) of about 0.01 cm2/V-s and ION/IOFF value of about 50 when doped with FeCl3. Results of measurement suggested that FeCl3 doping of P3HT could lead to a decrease of about 5 orders of magnitude in its contact resistance to Au electrodes, giving rise to two orders of magnitude increase of its apparent mobility. Therefore, it can be concluded that the contact resistances are the major limitation of performance of many PTFTs and need to be studied intensively in the future.
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Murad, Ary. "Development of new conjugated polymers for organic photovoltaics." Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/16317/.
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Mask, Walker. "MODELING THE CONDENSED-PHASE BEHAVIOR OF Π-CONJUGATED POLYMERS." UKnowledge, 2019. https://uknowledge.uky.edu/chemistry_etds/120.
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It is well established that the morphology and physical properties of an organic semiconducting (OSC) material regulate its electronic properties. However, structure-function relationships remain difficult to describe in polymer-based OSC, which are of particular interest due to their robust mechanical properties. If relationships among the molecular and bulk levels of structure can be found, they can aid in the design of improved materials. To explore and detail important structure-function relationships in polymer-based OSC, this work employs molecular dynamics (MD) simulations to study various π-conjugated polymers in different environments. Two independent investigations are discussed in this work. One investigation examines how the purposeful disruption of the π-conjugated backbone to increase the chain flexibility impacts the chain structure and packing in the condensed phase. This is done by adding a conjugation break spacer (CBS) unit of one to ten carbons in length into the monomer structure of diketopyrrolopyrrole-based polymers. It is found that trends in the folding and glass structure follow the increase and the parity (odd versus even) of the CBS length. The second investigation analyzes a variety of polymers and small molecule acceptor (SMA) blends to observe the effects of changing the shape of either component and the physical properties of the material, as well as the structure of the polymer chains. It is found that the conjugated core, the side chains, and the planarity or sphericity each influence the density and diffusion of the materials made.
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Halls, Jonathan James Michael. "Photoconductive properties of conjugated polymers." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368812.
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Pacios, Roberto. "Organic photovoltaic cells and photodiodes based on conjugated polymers." Thesis, Imperial College London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.417853.
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Marshall, Jonathan. "Carborane containing conjugated polymers for use in organic electronics." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/24949.
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Organic semiconductors have emerged as potential replacements for inorganic materials based on several promising advantages, such as their low-cost, high-throughput fabrication and tolerance for flexible substrates. While these attributes ensure that the use of organic semiconductors is appealing, further improvements in electronic performance and stability are still required. This work focuses on the design, synthesis and analysis of a novel range of organic semiconductors incorporating carborane units. Carboranes possess unusual properties which, in principle, make them highly attractive species to incorporate into optoelectronically active materials, although they have been largely untested as components of organic electronic devices. An uncommon three-dimensional delocalised bonding motif infers upon carboranes extreme thermal and chemical stability and a strong electron-withdrawing nature, traits that, if correctly exploited, could potentially lead to organic semiconductors with improved stabilities and optimised electronic properties. This thesis reports a number of approaches to the incorporation of carborane into semiconducting polymers. In the first, ortho-carborane is directly fused to the aromatic backbone via both carbon atoms. The novel difunctionalisation of benzocarborane, and its subsequent incorporation into two previously unreported polymer systems, is reported. Copolymerisation with electron-rich and electron-poor comonomers established that the incorporation of benzocarborane did not prevent electronic delocalisation along the polymer backbone, and that it acted as a mildly electron withdrawing comonomer. P-type behaviour in organic field effect transistors was observed. Based on these results, a second-generation monomer unit was synthesised, incorporating two fused thienyl rings and facilitating observable improvements in molecular ordering and charge-transporting behaviour. The second approach focuses on the attachment of carborane to the conjugated polymer backbone via the functionalisation of one of its carbon atoms, either directly or via a vinylene spacer. Hence carborane functionalised benzodithiophene monomers were prepared via a novel method of carborane C-arylation, before subsequent polymerisation with a range of electron accepting comonomers. The resultant polymers demonstrate OFET performance higher than that reported for non-carborane containing equivalents and exhibit promising solar cell performance. The final chapter details the attachment of various carboranes onto two polythiophene systems via a vinylene linker. Through careful consideration of carborane and vinyl bond stereochemistries, and pendant group spacing it was observed that optical, material, OFET and OPV properties of the resultant polymers could be controlled.
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Zhang, Xuan. "Dithienopyrrole-based conjugated materials for organic electronics." Diss., Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/37207.
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Dithienopyrrole-based conjugated materials, including oligomers and polymers, for potential organic electronic applications, were designed, synthesized and characterized. The optical and electrochemical properties of these materials were investigated, and their structure-property relationships were studied. Some of the materials can be oxidized (or reduced) chemically or electrochemically. Furthermore, the utility of these materials in organic electronic devices, such as OFETs and OPVs, were assessed. In OFETs, they can function as hole-transport materials with mobilities up to 4.8 × 10-2 cm2/(Vs), and one example serves as an ambipolar material with comparable hole and electron mobilities of 1.2 × 10-3 and 5.8 ×10-4 cm2/(Vs), respectively. Some of the materials can also be used as electron donors in OPVs in conjunction with PCBM, and exhibited power conversion efficiencies up to 1.4% after optimizations. They may also be used in other applications such as electrochromic devices, photodetectors, and optical limiting.
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Stedman, Troy C. "Thermal Fluctuations Tunneling in Doped Conjugated Polymers." Scholar Commons, 2015. https://scholarcommons.usf.edu/etd/5586.
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The possibility of using conducting polymers as organic alternatives to widely used inorganic materials for thermoelectric (TE) applications has received much attention in the past few decades. Since conducting polymers are generally inefficient compared to inorganic TE materials, research into their underlying transport mechanisms is required to improve their efficiency. We use a model based on the effects of local thermal fluctuations to characterize the transport in conducting polymer composites. With this model, full linear responses for the current and electronic heat current are obtained. From these responses, the local temperature dependent conductivity, electronic contribution to the thermal conductivity, and Seebeck coefficient are extracted and related to those of the composite material through an effective medium theory. The resulting simple expressions for the TE transport properties are easy to use and can improve our understanding of transport in conducting polymers. An example of how to use the model is given for a parabolic tunneling barrier and comparisons to experimental data are also provided.
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Zhu, Yan. "New conjugated polymers for organic electronics : synthesis, properties, and applications /." Thesis, Connect to this title online; UW restricted, 2006. http://hdl.handle.net/1773/9856.
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TUNG, WEI-YAO. "FUNCTIONALIZED CONJUGATED POLYMERS PROMOTED HIGH PERFORMANCE MATERIALS FOR ORGANIC ELECTRONIC DEVICES." University of Akron / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=akron1624317157379185.
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Righi, Sara <1983>. "Charge transport properties of organic conjugated polymers for photovoltaic applications." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6460/.
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Charge transport in conjugated polymers as well as in bulk-heterojunction (BHJ) solar cells made of blends between conjugated polymers, as electron-donors (D), and fullerenes, as electron-acceptors (A), has been investigated.
It is shown how charge carrier mobility of a series of anthracene-containing poly(p-phenylene-ethynylene)-alt-poly(p-phenylene-vinylene)s (AnE-PVs) is highly dependent on the lateral chain of the polymers, on a moderate variation of the macromolecular parameters (molecular weight and polydispersity), and on the processing conditions of the films. For the first time, the good ambipolar transport properties of this relevant class of conjugated polymers have been demonstrated, consistent with the high delocalization of both the frontier molecular orbitals.
Charge transport is one of the key parameters in the operation of BHJ solar cells and depends both on charge carrier mobility in pristine materials and on the nanoscale morphology of the D/A blend, as proved by the results here reported. A straight correlation between hole mobility in pristine AnE-PVs and the fill factor of the related solar cells has been found.
The great impact of charge transport for the performance of BHJ solar cells is clearly demonstrated by the results obtained on BHJ solar cells made of neat-C70, instead of the common soluble fullerene derivatives (PCBM or PC70BM). The investigation of neat-C70 solar cells was motivated by the extremely low cost of non-functionalized fullerenes, compared with that of their soluble derivatives (about one-tenth). For these cells, an improper morphology of the blend leads to a deterioration of charge carrier mobility, which, in turn, increases charge carrier recombination. Thanks to the appropriate choice of the donor component, solar cells made of neat-C70 exhibiting an efficiency of 4.22% have been realized, with an efficiency loss of just 12% with respect to the counterpart made with costly PC70BM.
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Wright, Helen. "Fused ring conjugated polymers and small molecules for organic-semiconductors." Thesis, University of Manchester, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.542784.
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Fused ring structures such as cyclopentadithiophenes (CPDT), fluorenes and dithienopyrroles have been shown to have low band gaps and extended conjugation lengths. Both of these properties make them interesting materials for organic semiconductor applications. It has been shown that increasing the planarity of building blocks, and in turn the polymer or molecule they are contained within, can improve charge transport by increasing π-π stacking. While the homo-polymers of dithienopyrrole, and alkene bridged CPDT and fluorene have low band gaps, it is possible to further reduce them by forming co-polymers, either by combination with an acceptor unit or by increasing the planarity of the polymer. Three families of small molecules and corresponding co-polymers were therefore synthesised using three main building blocks - alkene bridged CPDT, alkylidene fluorene and dithienopyrrole - combined with a series of co-monomers. In the cases of CPDT and dithienopyrrole two different alkyl chains were used with the aim of influencing solubility and solid-state packing. The optical and electrochemical properties were studied and trends determined. In addition physical and thermal properties were studied and for several of the small molecules, crystal structures and theoretical structures were also evaluated to probe intermolecular interactions in the solid state.During the synthesis of one alkylidene fluorene small molecule an unexpected impurity was isolated in which the bridging alkene of the fluorene had rearranged. Possible reasons for the formation were investigated and the properties of the compound studied.Several small molecules and one co-polymer were incorporated into preliminary OFET devices, although performance was limited by poor film formation. Film forming studies were also undertaken on the co-polymer.
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Kymakis, Emmanouil. "Organic photovoltaic devices based on conjugated polymers and carbon nanotubes." Thesis, University of Cambridge, 2003. https://www.repository.cam.ac.uk/handle/1810/272018.
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Cui, Chaohua. "Conjugated polymer and small-molecule donor materials for organic solar cells." HKBU Institutional Repository, 2014. https://repository.hkbu.edu.hk/etd_oa/37.
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This thesis is dedicated to developing conjugated polymer and small-molecule donor materials for solution-processable organic solar cells. To begin with, a brief introduction of organic solar cells (OSCs) and an overview of donor materials development were presented in Chapter 1. In chapter 2, we used carbon-carbon triple bands as linkage of the TVT unit to develop a new building block, ATVTA. Small molecules S-03, S-04, and S-05 with ATVTA as building block showed broad absorption spectra and low-lying HOMO energy levels. S-01 with TVT unit and S-02 with AT2 as building block were also synthesized for clear comparison. OSCs devices based on S-01 and S-02 showed a Voc of 0.88 V and 0.89 V, respectively. The device based on S-03 exhibited a high Voc of 0.96 V, leading to a PCE of 2.19%. The devices based on S-04 and S-05 afforded a notable Voc over 1.0 V. The results demonstrate that ATVTA unit is a promising building block for extending π conjugation of the molecules without pulling up their HOMO energy levels. Chapter 3 focused on the development of 2D-conjugated small-molecule donor materials. The 2D-conjugated small molecule S-06 possesses excellent solution processability, broad absorption feature, respectable hole mobility and good film-forming morphology. The conjugated thiophene side chain not only effectively extends the absorption spectrum, but also lowers the HOMO energy level, which is desirable for obtaining high Voc. The BHJ OSCs based on S-06:PC70BM (1:0.5, w/w) afforded a high PCE of 4.0% and a notable FF of 0.63 without any special treatment needed. This preliminary work demonstrates that this kind of 2D-conjugated small molecules offer a good strategy to design new photovoltaic small molecule-based donor materials with high FF and Voc for high-efficiency OSCs. The consistently developed two 2D-conjugated small molecules S-07 and S-08 also possess low-lying HOMO energy levels. OSC device based on S-07:PC60BM (1:3, w/w) afforded a notable Voc of 0.96 V, with a PCE of 2.52%. BHJ devices based on S-08 will be fabricated and tested to investigate its photovoltaic properties in the near future. We developed a series of oligothiophenes with platinum(Ⅱ) as the building block in Chapter 4. These small metallated conjugated small molecules exhibited broad spectra and relatively low-lying HOMO energy levels in the range of –5.27 eV to –5.40 eV. Introducing platinum(Ⅱ) arylene ethynylenes as building block can be considered as an approach to obtain small-molecule donors with satisfactory absorption features and HOMO energy levels. Nevertheless, due to the low FF, the PCEs of these donor materials based devices are lower than 2%. Fine tuning the film morphologies of this kind of metallated small-molecule donor materials should be carried out to improve their photovoltaic performance. We addressed an efficient approach to improve the photovoltaic properties by side chain engineering in 2D-conjugated polymers in Chapter 5. Considering the fact that the Voc of PBDTTT based devices is less than 0.8 V, we introduced alkylthio substituent on the conjugated thiophene side chains of the 2D-conjugated copolymer to further improve the photovoltaic performance of the 2D-conjugated copolymers PBDTTTs. The weak electron-donating ability of the alkylthio side chains effectively down-shifted the HOMO energy level of PBDTT-S-TT by 0.11 eV in comparison to the corresponding polymer with alkyl substitution on the conjugated thiophene side chains. The PSC device based on PBDTT-S-TT showed an enhanced Voc of 0.84 V, which is among the highest one in the reported copolymers based on BDT and TT units, leading to an enhanced PCE of 8.42%. The results indicate that molecular modification by introducing alkylthio side chain will be a promising strategy to broaden the absorption, down-shift the HOMO energy level and increase the hole mobility of the low band gap 2D-conjugated polymers for further enhancing the photovoltaic performance of PSCs. PBDTT-O-TT-C and PBDTT-S-TT-C were developed to further study the conclusion. We found that OSC device based on PBDTT-S-TT-C with alkylthio side chain also demonstrated a high Voc of 0.89 V, with a PCE of 6.85% when processed with 3% DIO additive
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Apaydin, Dogukan Hazar. "Electrochromic And Photovoltaic Applications Of Conjugated Polymers." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614481/index.pdf.
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Three new azobenzene containing conjugated monomers were designed and synthesized. Resulting monomers were characterized by means of 1H NMR and 13C NMR techniques. Monomers (E)-1,2-bis(4-(thiophen-2-yl)phenyl)diazene (M1), (E)-1,2-bis(4-(4-hexylthiophen-2-yl) phenyl) diazene (M2) and (E)-1,2-bis(2-fluoro-4-(4-hexylthiophen-2-yl)phenyl) diazene (M3) were electrochemically polymerized using cyclic voltammetry to give polymers P1, P2 and P3. The polymers were subjected to spectroelectrochemical and kinetic studies in order to obtain information about their elecrochromic characteristics. P1 and P2 were pale-yellow in their neutral states and blue in oxidized states while P3 showed multichromic property due to having polaron bands in visible region of the spectrum. Addition of fluorine atoms to the backbone of P3, lowered the LUMO level of P3 thus gained the polymer n-doping property.
In the second part of this thesis poly((9,9-dioctylfluorene)-2,7-diyl-(4,7-bis(thien-2-yl) 2-dodecyl-benzo[1,2,3]triazole)) (PFTBT) polymer was mixed with common electron acceptor Phenyl-C61-butyric acid methyl ester (PCBM) and used in organic solar cell applications. Active layers containing PFTBT and PCBM were spin casted on ITO coated substrates at varying rotational speeds to obtain active layer thicknesses having different values. Thickness of the active layer was optimized so was the efficiency of organic solar cells. As a result of this optimization study, efficiency of PFTBT containing organic solar cells were increased to 1.06% which is a higher value than previosly reported literature results.
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Jagtap, Subodh Prakash. "Design and synthesis of and π-stacked conjugated oligomers and polymers." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/47574.
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Interchain interactions between π-systems have a strong effect on the properties of conjugated organic materials that find application in devices such as light emitting diodes (OLEDs), organic photovoltaics (OPVs), and field effect transistors (FETs). We have prepared covalently-stacked oligo(1,4-phenylene ethynylene)s and oligo(1,4-phenylene vinylene)s to study the influence of chain-chain interactions on the electronic structure of closely packed conjugated units. These serve as models for segments of conjugated materials in thin film devices. Extension of this concept has allowed us to prepare multi-tiered systems that display the influence of pi-stacking. The stacked architectures were prepared by multi-step synthesis of the scaffolds, followed by metal-catalyzed cross coupling reactions (Sonogashira, Heck, Suzuki couplings) to incorporate the conjugated oligomers. The optical and electrochemical properties of these stacked compounds and polymers were compared to their unstacked linear counterparts. These studies provide a platform for the exploration of the nature of charge carriers and excitons in a broad class of materials that have significant potential in addressing challenges in power generation, lighting and electronics.
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Mitchell, William John. "Polymer-electrode interactions in light emitting diodes." Thesis, University of Oxford, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289406.
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Giraud, Lauriane. "Bis-vanillin substrates as source of π-conjugated polymers for organic electronic." Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0404.
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Ces travaux de thèse portent sur la synthèse de polymères π-conjugués biosourcés issus de la vanilline, visant des applications potentielles en électronique organique (photovoltaïque ou Organic Light Emitting Diode, OLED). Des polyazométhines de masses molaires élevées, issus de la copolymérisation entre la divanilline et différentes diamines, ont été obtenus par polymérisation sous irradiation micro-onde durant 5 minutes puis séchage à l’évaporateur rotatif. Ces derniers ont une absorbance dans le proche UV mais un chemin de conjugaison très court, comme l’a révélé l’analyse de molécules modèles. Pour améliorer ce chemin de conjugaison, une molécule à base de divanilline a été synthétisée avec les fonctions aldéhyde en position para par rapport à la liaison entre les deux cycles aromatiques. Cette para-divanilline, encore jamais décrite, a été utilisée pour la synthèse de polyazomethines. Ces derniers présentent également un court chemin de conjugaison en raison de l’encombrement stérique entre les deux groupes phényle. Une dernière famille de polymère a alors été étudiée : les polythiazolothiazoles à base de divanilline. Ces polymères présentent des propriétés d’émission qui se caractérisent par une émission dans le bleu en solution et dans le jaune à l’état de film. Des molécules modèles à base de benzothiazole ont également été synthétisées et présentent un rendement quantique de fluorescence de 20% ainsi qu’un empilement π en « chevrons », leur conférant un fort potentiel pour diverses applications en électronique organiqueThe objective of this PhD is to synthesize π-conjugated bio-based polymers from vanillin, with potential applications in the field of organic electronic (photovoltaic, Organic Light Emitting Diode, OLED). Polyazomethines with high molar masses were obtained via the copolymerization of divanillin with various diamines. This polycondensation was performed in 5 minutes under microwave irradiation, followed by solvent removal using a rotary evaporator. Divanillin-based polyazomethines absorb in the near-UV range but have a short conjugation pathway, as revealed investigations on model compounds. To improve this conjugated pathway, a divanillin-based molecule bearing aldehyde functions in para positions with respect to the link between the rings, was designed. This so-called para-divanillin, never reported before, was copolymerized to yield polyazomethines. These latter polymers also have a short conjugation pathway due to steric hindrance between the two aromatic rings of the para-divanillin skeleton. A last family of divanillin-based polymers was thus investigated: polythiazolothiazoles. The latter exhibit specific emission properties as they emit in the blue range in solution and in the yellow range in films. Benzothiazole-based model compounds were also synthesized and exhibited a fluorescence quantum yield of 20% and “herringbone-like” π-stacking, giving them a strong potential for various organic electronic applications
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Huang, Wei [Verfasser]. "Conjugated porous polymers for visible light-induced organic transformations / Wei Huang." Mainz : Universitätsbibliothek Mainz, 2017. http://d-nb.info/1143985516/34.
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Shaw, Paul E. "Measurements of exciton diffusion in conjugated polymers." Thesis, University of St Andrews, 2009. http://hdl.handle.net/10023/831.
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The exciton diffusion length, which is the distance an exciton can diffuse in its lifetime, is an important parameter that has a critical impact on the operation of many organic optoelectronic devices, including organic solar cells, light emitting diodes and lasers. Knowledge of the exciton diffusion length can be a powerful aid for the design and optimisation of these devices. This thesis details the development of techniques based on time-resolved fluorescence for measuring the exciton diffusion in organic semiconductors. Two main methods were used to investigate exciton diffusion in the conjugated polymers P3HT, MEH-PPV and F8BT: the surface quenching technique and exciton-exciton annihilation. In particular, the surface quenching technique was adapted to avoid some of the potential pitfalls that have plagued earlier measurements. Using a titania quencher, measurements were performed using the surface quenching technique and fitted with an exciton diffusion model, allowing the calculation of the exciton diffusion length. Results from measurements of the exciton-exciton annihilation rate, which is a diffusion controlled process, where in good agreement with those from surface quenching, confirming the robustness of this twofold approach. A novel method for the control of the β-phase conformation in PFO films was used to produce films containing varying concentrations of β-phase. Exciton-exciton annihilation was used to investigate exciton diffusion in these films, revealing a gradual rise with increasing β-phase fraction due to improved interconnectivity. This work demonstrates how simple processing techniques can be used to control both film morphology and the exciton diffusion. The thickness dependence of the photoluminescence lifetime in conjugated polymers is a phenomenon that has so far received little attention and, thus, remained unexplained. This study demonstrates that it is not due to exciton quenching by external factors, but can be explained by a change in the morphology with decreasing film thickness.
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Zhan, Hongmei. "Synthesis, characterization and optoelectronic applications of new conjugated organic and organometallic polymers." HKBU Institutional Repository, 2011. http://repository.hkbu.edu.hk/etd_ra/1240.
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Daoud, Walid. "Synthesis of conjugated polymers and their use in photovoltaic cells." Thesis, University of Sheffield, 2002. http://etheses.whiterose.ac.uk/14469/.
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Mori, Daisuke. "Development of Polymer Blend Solar Cells Composed of Conjugated Donor and Acceptor Polymers." 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/199331.
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Luo, Yanqi. "Interfacial Interactions between Carbon Nanoparticles and Conjugated Polymers." DigitalCommons@CalPoly, 2014. https://digitalcommons.calpoly.edu/theses/1291.
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Conjugated polymer based electronics, a type of flexible electronic devices, can be produced from solution by traditional printing and coating processes in a roll-to-roll format such as papers and graphic films. This shows great promise for the emerging energy generation and conversion. The device performance of polymer electronics is largely dependent of crystalline structures and morphology of photoactive layers. However, the solution crystallization kinetics of conjugated polymers in the presence of electron acceptor nanoparticles has not been fully understood yet. In this study, solution crystallization kinetics of poly (3-hexylthiophene) in the presence of carbon nanotubes and graphene oxide has been investigated by using UV-visible absorption spectroscopy and transmission electron microscope. Various kinetics parameters such as crystallization temperature, polymer solution concentration and nanoparticle loading will be discussed. The crystallization rate law and fold surface free energy will be addressed by using polymer crystallization theory of heterogeneous nucleation. This fundamental study will provide a foundation of fabricating high efficiency polymer based electronics.
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Thomsen, Elizabeth Alice. "Characterisation of materials for organic photovoltaics." Thesis, St Andrews, 2008. http://hdl.handle.net/10023/462.
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Watt, Shannon L. "Synthesis and Characterization of Regioregular, Amphiphilic Semifluoroalkyl-Substituted Polythiophenes and Cofacial Bis(oligothienyl)naphthalenes." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19787.
Full textAbstract:
Conjugated polymers and oligomers have been widely studied based on their wide range of useful properties and applications. Given the importance of self-assembly and charge transfer in the development of conjugated materials for use in electronic applications, it is crucial to: (i) prepare functional materials by molecular design, (ii) evaluate the structure-property relationships of new materials, and (iii) develop fundamental understanding of electronic structure and charge transport behavior.
The use of conjugated polymeric materials in electronic applications relies on control of the assembly and orientation of the polymer chains in the solid state. Conjugated polymers with liquid crystalline behavior could be used to implement an additional level of control over orientation and resultant properties. Substitution of the conjugated polythiophene backbone with semifluoroalkyl side chains (i.e., the diblock -(CH2)m(CF2)nF) has afforded materials with unusual properties. The mutual immiscibility of the aromatic backbone, the alkyl side-chain segments, and the fluoroalkyl side-chain termini provides control over supramolecular packing. A series of eight polymers has been synthesized, in which the lengths of the alkyl (m) and fluoroalkyl (n) segments are varied. One regiorandom analogue and two poly(3-alkylthiophene)s were also synthesized for comparative purposes. The structure, molecular weight, and regioregularity of the polymers were evaluated using a variety of techniques.
The semifluoroalkyl-substituted polymers have been systematically studied to determine the effect of side chain length and m:n block ratios on their solution state, liquid crystalline, and solid state properties. The effect of side chains on conjugation was determined, where solubility allowed, by solution-state UV-visible and fluorescence spectroscopy. The thermal and liquid crystalline properties of the homopolymers were evaluated by DSC, variable-temperature X-ray diffraction, and polarized optical microscopy. Several semifluoroalkyl-substituted polythiophene homologues show liquid crystalline behavior.
Molecular packing and charge transport are key factors governing the use of conjugated materials in electronic applications. A wide variety of oligomers have been studied as models for charge migration in conjugated polymers. One-dimensional models do not adequately represent two-dimensional charge transport; thus, a variety of two-dimensional, covalently-linked models have been developed. Previous work by our group, and others, led to the proposal of bis(oligothienyl) compounds as models to study the interaction of the ð-conjugated chains. Previous reports by other researchers described the synthesis and characterization of hydrogen-terminated analogues of 1,8-bis(oligothienyl)naphthalenes. However, these materials proved to be unsuitable for use as charge transport models, as they were subject to irreversible polymerization upon oxidation. Installation of methyl groups at the terminal a-positions of 1,8-bis(oligothienyl)naphthalenes allowed us to create a series of models in which conjugated chains are held in close proximity. This provides access to multiple redox states, and future systems based on these molecules may be used as models for charge transport or as functional materials for incorporation into devices.
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Skrypnychuk, Vasyl. "Vertical charge transport in conjugated polymers." Doctoral thesis, Umeå universitet, Institutionen för fysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-133180.
Full textAbstract:
Conjugated polymers are novel organic electronic materials highly important for organic photovoltaic applications. Charge transport is one of the key properties which defines the performance of conjugated polymers in electronic devices. This work aims to explore the charge transport anisotropy in thin films of P3HT, one of the most common conjugated polymers. Using X-ray diffraction techniques and charge transport measurements, the relation between vertical charge transport through thin P3HT films and structure of the films was established. It was shown that particular orientations of crystalline domains of P3HT, namely face-on and chain-on, are beneficial for vertical charge transport. These orientations provide the efficient pathways for the charges to be transported vertically, either via π-π stacking interaction between the adjacent conjugated chains, or via the conjugated chain backbones. It was also demonstrated that particular orientations of crystallites are favourable for the formation of interconnected percolated pathways providing enhanced vertical charge transport across the film. Deposition of P3HT on most commonly used silicon substrates typically results in the formation of mostly edge-on orientation of crystallites which is unfavourable for vertical charge transport. Nanoimprint lithography was demonstrated as a powerful processing method for reorienting the edge-on crystalline domains of P3HT into chain-on (vertical) orientation. It is also shown that thin P3HT films with preferentially face-on orientations of crystallites can be deposited on graphene surface by spin coating. Using patterning of thin P3HT films by nanoimprint lithography, unprecedentedly high average vertical mobilities in the range of 3.1-10.6 cm2 V-1 s-1 were achieved in undoped P3HT. These results demonstrate that charge transport in thin films of a relatively simple and well-known conjugated polymer P3HT can be significantly improved using optimization of crystallinity,orientation of crystallites, polymer chain orientation and alignment in the films.
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Cheung, Wai-kei, and 張偉基. "Low band-gap donor-acceptor polymers and heterolyptic ruthenium complex containing polymers for photovoltaic applications." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B47753006.
Full textAbstract:
A series of low band-gap conjugated polymers with intramolecular charge
transfer properties were synthesized and bulk heterojunction devices based on
these polymers were fabricated. The electrochemical and photophysical properties
of the polymers were tuned by using different electron withdrawing molecules or
ruthenium complexes as the comonomer. Preliminary results suggested that the
electronic structures of the polymer were significantly altered by the incorporation
of different acceptor units. The polymers also demonstrated intense absorption
bands in the visible region, indicating that they are suitable photoactive materials
in bulk heterojunction devices.
The synthesis and characterization of a series of organic donor-acceptor
copolymers were studied. All of the polymers contained alternating
cyclopenta[2,1- b:3,4-b’]dithiophene (CPDT) units. The effects of the different
acceptor monomers were evaluated. The electron-withdrawing carboxylate and
amide functional groups of the acceptors were found to effectively stabilize the
HOMO levels of the polymer, and the optical band-gaps were significantly
reduced. Bulk heterojunction devices were fabricated using the polymers and
6,6-phenyl C61 butyric acid methyl ester (PCBM) as donors and acceptors
respectively. These devices exhibited high open circuit voltage (Voc) up to 0.86 V.
The extended photosensitizing range was confirmed by the external quantum
efficiency (EQE) spectra. The device performance was further improved by
optimizing the active layer thickness and applying 1,8-diiodooctane in the blend
solution.
A new synthetic route to novel ruthenium containing polymers was also
reported. [Ru(L)(L’)Cl2] complexes (L and L’ = bidentate N^N ligands) with a
dibromo-substituted ligand were found to be polymerizable by Stille cross-coupling
reaction. The subsequent displacement of the chloride ligands by
thiocyanate was highly effective and the structures of the target polymers were
fully characterized. The main chain absorption showed a significant red-shift upon
metal coordination and the metal-to-ligand charge transfer (MLCT) of the
complex strengthens the photon harvesting ability of the polymer. The dual
function of these Ru(II) complexes demonstrated a new avenue to develop new
classes of optoelectronic materials. The extent of _-delocalization of the ancillary
ligands also showed interesting effects on the electronic properties of the
polymers. Bulk heterojunction devices were fabricated. Photovoltaic response was
observed in these devices, and the device performance can be improved by further
modifying the surface morphology of the blend films.published_or_final_version
Chemistry
Master
Master of Philosophy
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Goossens, Mark. "Ultrafast organic lasers and solid-state amplifiers." Thesis, St Andrews, 2007. http://hdl.handle.net/10023/315.
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Haylett, Nick. "Investigations into the synthesis, characterisation and properties of some conjugated organic polymers." Thesis, Durham University, 1995. http://etheses.dur.ac.uk/5406/.
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This thesis describes some work directed to the synthesis and attempted synthesis of some conjugated organic polymers. Chapter I provides a general review of the field of conjugated polymers, including their synthesis and interesting physical properties. Chapter 2 gives an overview of the field of poly(arylene vinylene)s, including their physical properties, their electrolununescence and potendal application in polymer light emitting devices and a review of the McMurry reaction. The synthesis of poly(4,4'-diphenylene diphenylvinylene) via the reductive coupling of 4,4'.dibenzoyldiphenyl is described along with work aimed at optimising this polymerisation. Characterisation details of poly(4,4'-dipheny]enediphenylvinylene) are given and results from an investigation into the electroluminescence of the polymer are recorded. The extension of this type of polymerisation reaction to include other diketone monomers is described along with the characterisation of the materials produced. Chapter 3 describes the proposed ring opening metathesis polymerisation of some quinone substituted norbomadiene monomers in an attempt to synthesise a conjugated redox polymer system. The attempted ROMP of the monomers using either Mo(N-2,6.i- Pr(_2)-C(_6)H(_3))(CHR)(OCMe(_3)) or Ru((C(_6)H(_12))(_3)P)2a2(CH=CH=CPh(_2)) is reported. Chapter 4 reports on the attempted development of a novel synthetic route to polyaniline via an triphenylarsine imine intermediate. Work concerning a model reaction and the spectral identification of the intermediate and results from die attempted synthesis of a polyanihne related polymer are reported.
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Kerszulis, Justin Adam. "Reading the rainbow: tailoring the properties of electrochromic polymers." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53071.
Full textAbstract:
The completion of the color palette has yielded a family of electrochromic polymers (ECPs) each able to absorb in unique regions across the visible spectrum. Synthetically, by varying the electronic content of phenylene type moieties coupled with the donor 3,4-propylenedioxythiophene (ProDOT), high band gaps can be achieved absorbing short wavelength light, yielding a family of yellow-to-transmissive electrochromic polymers. Using the synthetic approach to tune specific absorptions in a discrete region of the visible spectrum, a family of electrochromic polymers that possess sharpened or broadened absorption spectra relative to electrochromic materials previously produced has been developed. By varying the steric hindrance of dioxythiophenes along a conjugated backbone, new hues of magenta and blue have been achieved. Through progressively adding more steric hindrance and twisting the polymer backbone, the absorbance of a polymer can be pushed towards shorter wavelengths, allowing more red light and less blue light to pass through a film. This unequal passing of long and short wavelengths reduces the overall purple color that is normally exhibited by a previous magenta ECP, thereby giving brighter, truer magenta colored materials. By reducing steric hindrance and relaxing the polymer backbone, the opposite can be achieved: pushing the absorbance of a polymer to longer wavelengths allows more blue and less red light to transmit. These polymers also exhibit highly transmissive oxidized states that are attainable at low potentials. In the quest to achieve black (or dark as defined by low L*) to transmissive ECPs with suitable contrast for window or eyewear applications, a relaxed donor-acceptor architecture has been explored. These materials give broad neutral state absorptions with a %Tint (380-780 nm) > 50 %, bringing these materials closer to realization.
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Ho, Cheuk Lam. "Conjugated metal-organic phosphorescent materials and polymers containing fluorene and carbazole units." HKBU Institutional Repository, 2007. http://repository.hkbu.edu.hk/etd_ra/808.
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Liyanage, Arawwawala Don T. "FLUORINATED ARENE, IMIDE AND UNSATURATED PYRROLIDINONE BASED DONOR ACCEPTOR CONJUGATED POLYMERS: SYNTHESIS, STRUCTURE-PROPERTY AND DEVICE STUDIES." UKnowledge, 2013. http://uknowledge.uky.edu/chemistry_etds/23.
Full textAbstract:
FLUORINATED ARENE, IMIDE AND LACTAM-FUNCTIONALIZED DONOR ACCEPTOR CONJUGATED POLYMERS: SYNTHESIS, STRUCTURE-PROPERTY AND DEVICE STUDIES
After the discovery of doped polyacetylene, organic semiconductor materials are widely studied as high impending active components in consumer electronics. They have received substantial consideration due to their potential for structural tailoring, low cost, large area and mechanically flexible alternatives to common inorganic semiconductors. To acquire maximum use of these materials, it is essential to get a strong idea about their chemical and physical nature. Material chemist has an enormous role to play in this novel area, including development of efficient synthetic methodologies and control the molecular self-assembly and (opto)-electronic properties. The body of this thesis mainly focuses on the substituent effects: how different substituent’s affect the (opto)-electronic properties of the donor-acceptor (D-A) conjugated polymers. The main priority goes to understand, how different alkyl substituent effect to the polymer solubility, crystallinity, thermal properties (eg: glass transition temperature) and morphological order. Three classes of D-A systems were extensively studied in this work. The second chapter mainly focuses on the synthesis and structure-property study of fluorinated arene (TFB) base polymers. Here we used commercially available 1,4-dibromo-2,3,5,6-tetrafluorobenzene (TFB) as the acceptor material and prepare several polymers using 3,3’-dialkyl(3,3’-R2T2) or 3,3’-dialkoxy bithiophene (3,3’-RO2T2) units as electron donors. A detail study was done using 3,3’-bithiophene donor units incorporating branched alkoxy-functionalities by systematic variation of branching position and chain length. The study allowed disentangling the branching effects on (i) aggregation tendency, intermolecular arrangement, (iii) solid state optical energy gaps, and (iv) electronic properties in an overall consistent picture, which might guide future polymer synthesis towards optimized materials for opto-electronic applications. The third chapter mainly focused on the structure-property study of imide functionalized D-A polymers. Here we used thiophene-imide (TPD) as the acceptor moiety and prepare several D-A polymers by varying the donor units. When selecting the donor units, more priority goes to the fused ring systems. One main reason to use imide functionality is due to the, open position of the imide nitrogen, which provides an attaching position to alkyl substituent. Through this we can easily manipulate solubility and solid state packing arrangement. Also these imide acceptors have low-lying LUMOs due to their electron deficient nature and this will allow tuning the optical energy gap by careful choice of donor materials with different electron donating ability. The fourth chapter mainly contribute to the synthesis and structure property study of a completely novel electron acceptor moiety consist of a unsaturated pyrrolidinone unit known as Pechmann dye (PD) core. Pechmann dyes are closely related to the Indigo family. This can refer as 3-butenolide dimer connected via an alkene bridge, containing a benzene ring at the 5 and 5’ positions of the lactone rings. We have prepared several D-A polymers using this PD system with benzodithiophene (BDT) as the donor unit. Different to common D-A polymers the HOMO and LUMO of the PD acceptor moiety are energetically located within the gap of the BDT, so that the electronic and optical properties (HOMO-LUMO transition) are dictated by the PD properties. The promising electronic properties, band gaps, high absorption coefficients and broad absorption suggest this new D-A polymers as an interesting donor material for organic solar cell (OSC) applications.
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Twomey, Megan. "Conjugated Polymer-Based Biomaterials Through Controlled Self-Assembly." FIU Digital Commons, 2016. http://digitalcommons.fiu.edu/etd/2452.
Full textAbstract:
Synthetic polymeric materials have gained significant use as biological materials (biomaterials) in biomedical and pharmaceutical applications. As a result, a demand for well-defined polymers with tunable properties has emerged. The synthetic versatility of polymeric biomaterials allows the opportunity to understand the structure-property relationship of materials and their cellular interactions. A novel class of polymeric biomaterials are conjugated polymers (CPs), which possess desirable physicochemical and excellent photophysical properties, including inherent fluorescence. The synthetic versatility of CPs allows easy modification of the conjugated backbone to tune emission and side chain structures to adjust biocompatibility through increased water solubility, controlled biodegradability, and incorporation of targeting units. The aim of this dissertation is to better understand conjugated polymer nanoparticle (CPN) structure and self-assembly in an aqueous environment, and how those structural features affect cellular interactions to establish a structure-function relationship.
This work presents the fabrication of several different CPNs for cancer cell targeting and labelling, and differentiation of biologically important molecules. Core−shell nanoparticles were prepared using a semi-flexible cationic CPN complexed with hyaluronic acid (HA), a polyanion. The resulting CPNs exhibited high cancer cell specificity with low adsorption to normal cells, as a result of HA’s affinity towards overexpressed receptors on cancer cell surface. A systematic investigation on the aggregation properties of CPNs that vary by side chain and backbone structures in response to different biologically important anionic polysaccharides in a complex biological medium was conducted. Mitochondria-specific CPNs were fabricated from a semi-flexible CPN modified with the mitochondrial-targeting triphenylphosphonium (TPP) group. The subcellular localization and cellular toxicity were dependent on backbone flexibility, hydrophilicity, and molecular weight. Dual-targeting CPNs grafted with folic acid (FA) side chains and complexed with hyaluronic acid (HA) were fabricated for improved uptake and bioimaging of cancer cells.
The work presented here shows how modifications to CPN backbone and side chain structures modulate their cellular interactions. The physicochemical and biophysical properties of CPNs affect biocompatibility and understanding those properties will lead to the development of novel CP-based biomaterials.
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Woody, Kathy Beckner. "Design, synthesis and characterization of self-assembling conjugated polymers for use in organic electronic applications." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/43627.
Full textAbstract:
Conjugated polymers comprise some of the most promising materials for new technologies such as organic field effect transistors, solar light harvesting technology and sensing devices. In spite of tremendous research initiatives in materials chemistry, the potential to optimize device performance and develop new technologies is remarkable. Understanding relationships between the structure of conjugated polymers and their electronic properties is critical to improving device performance. The design and synthesis of new materials which self-organize into ordered nanostructures creates opportunities to establish relationships between electronic properties and morphology or molecular packing. This thesis details our progress in the development of synthetic routes which provide access to new classes of conjugated polymers that contain dissimilar side chains that segregate or dissimilar conjugated blocks which phase separate, and summarizes our initial attempts to characterize these materials. Poly(1,4-phenylene ethynylene)s (PPEs) have been used in a variety of organic electronic applications, most notably as fluorescent sensors. Using traditional synthetic methods, asymmetrically disubstituted PPEs have irregular placement of side chains on the conjugated backbone. Herein, we establish the first synthetic route to an asymmetrically substituted regioregular PPEs. The initial PPEs in this study have different lengths of alkoxy side chains, and both regioregular and regiorandom analogs are synthesized and characterized for comparison. The design of amphiphilic structures provides additional opportunities for side chains to influence the molecular packing and electronic properties of conjugated polymers. A new class of regioregular, amphiphilic PPEs has been prepared bearing alkoxy and semifluoroalkoxy side chains, which have a tendency to phase separate. Fully conjugated block copolymers can provide access to interesting new morphologies as a result of phase separation of the conjugated blocks. In particular, donor-acceptor block copolymers that phase separate into electron rich and electron poor domains may be advantageous in organic electronic devices such as bulk heterojunction solar cells, of which the performance relies on precise control of the interface between electron donating and accepting materials. The availability of donor-acceptor block copolymers is limited, largely due to the challenges associated with synthesizing these materials. In this thesis, two new synthetic routes to donor-acceptor block copolymers are established. These methods both utilize the catalyst transfer condensation polymerization, which proceeds by a chain growth mechanism. The first example entails the synthesis of a monofunctionalized, telechelic poly(3-alkylthiophene) which can be coupled to electron accepting polymers in a subsequent reaction. The other method describes the first example of a one-pot synthesis of a donor-acceptor diblock copolymer. The methods of synthesis are described, and characterization of the block copolymers is reported.
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Yang, Kun. "CONJUGATED POLYMERS AND SMALL MOLECULES WITH LATENT HYDROGEN-BONDING FOR ORGANIC ELECTRONIC APPLICATIONS." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron149083508357808.
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Yau, Chin Pang. "Design, synthesis and characterisation of conjugated polymers containing reactive functionality for organic photovoltaics." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/33159.
Full textAbstract:
The nanoscale morphology of the active layer in organic photovoltaic devices is critical to their performance. Blend morphologies can be manipulated by using a variety of additives, co-solvents and by thermal annealing. However, one crucial issue for any organic photovoltaic device is operational lifetime, which is largely dictated by changes in the active layer morphology. Such changes may be due to reordering of the polymer material, or diffusion and aggregation of fullerene derivatives to a more thermodynamically stable state. This reordered structure can potentially have detrimental effect by losses in interfacial surface area and an increase in exciton recombination. Many novel polymers are designed without this consideration and may be susceptible to this type of degradation. Herein, we explore a variety of approaches to stabilise the blend morphology, principally by the incorporation of various reaction functionalities onto the polymer backbone. The three main areas which have been investigated are; varying of acceptor strengths, chain end modifications with various crosslinking chemistries and thermally cleavable leaving groups. Firstly, poly(dithienogermole-benzothiadiazole) analogues are synthesised to investigate how changes to the acceptor strength of the D-A co-polymers will affect the bulk heterojunction morphology and polymer performance. Then the synthesis and functionalisation of benzotriazole in poly(cyclopentadithiophene-benzotriazole) with alkyl bromine crosslinking groups and thienopyrroledione in poly(dithienogermole-thienopyrroledione), with both alkyl bromide & alkyl oxetane crosslinking groups was investigated. Further studies will investigate the effects on material and optoelectronic properties as well as device performance in OPV and suitability of additives with crosslinking. Lastly, we explore the incorporation of thermal cleavable BOC groups on thienopyrroledione, in poly(cyclopentadithiophene-thienopyrroledione), the deprotection of Boc in polymeric materials and its effects on material and optoelectronic properties.
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Larsson, Oscar. "Empirical parameterization of organic electrochemical transistors." Thesis, Linköping University, Department of Science and Technology, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-1503.
Full textAbstract:
In this diploma work, organic electrochemical transistors based on PEDOT:PSS have been studied, focusing on the influence of the geometry and physical dimensions on the transistor characteristics. The geometrical parameters studied are the area ratio between the gate and channel, the channel width and the channel length. Each parameter has been varied in five steps with each step containing three identical transistors. Results concerning the geometrical influence of the linear region resistance, the saturation current (density) and the on/off ratio are presented and discussed. Also, empirical curve-fits of the geometrical influence on the linear region resistance and the saturation current have been performed. In addition, tentative results of the locus of the saturation current versus saturation voltage for specific transistors have been obtained.
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Manuelli, Alessandro. "Influences of Printing Techniques on the Electrical Performances of Conjugated Polymers for Organic Transistors." Doctoral thesis, Universitätsbibliothek Chemnitz, 2007. http://nbn-resolving.de/urn:nbn:de:swb:ch1-200700044.
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The discovery of conducting and semiconducting polymers has opened the possibility to produce
integrated circuits entirely of plastic with standard continuous printing techniques. Nowadays
several of this polymers are commercial available, however the performances of this materials are
strongly affected by their supramolecular order achieved after deposition. In this research, the
influence of some standard printing techniques on the electrical performances of conjugated
polymers is evidenced in order to realise logic devices with these materials.
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Said, Elias. "Electrolyte-Based Organic Electronic Devices." Licentiate thesis, Linköping : Department of Science and Technology, Linköping University, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-9955.
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Liang, Zhiming. "MORPHOLOGICAL AND ENERGETIC EFFECTS ON CHARGE TRANSPORT IN CONJUGATED POLYMERS AND POLYMER-NANOWIRE COMPOSITES." UKnowledge, 2018. https://uknowledge.uky.edu/chemistry_etds/99.
Full textAbstract:
Organic semiconductors have wide applications in organic-based light-emitting diodes, field-effect transistors, and thermoelectrics due to the easily modified electrical and optical properties, excellent mechanical flexibility, and solution processability. To fabricate high performance devices, it is important to understand charge transport mechanisms, which are mainly affected by material energetics and material morphology. Currently it is difficult to control the charge transport properties of new organic semiconductors and organic-inorganic nanocomposites due to our incomplete understanding of the large number of influential variables. Molecular doping of π-conjugated polymers and surface modification of nanowires are two means through which charge transport can be manipulated. In molecular doping, both the energetics and microstructures of polymer films can be changed by controlling the degree of oxidation of the conjugated polymer backbone. For surface modification of inorganic nanowires, the energetics and morphology can be influenced by the properties of the surface modifiers. Meanwhile, the energy band alignment, which can be controlled by surface modification and molecular doping, may also alter the charge transport due to the variation in energetic barriers between the transport states in the organic and inorganic components.
To reveal the effects of morphology and energetics on charge transport in conjugated polymers and organic-inorganic nanocomposites, the influence of surface modifier on the electrical and morphological properties of nanocomposites was first probed. Silver nanowires modified with different thiols were blended with poly (3,4-ethylenedioxythiophene)-poly(styrenesulfonate)(PEDOT:PSS) to fabricate thin films. The modified nanowires provided a means of controllably altering the nanowire dispersability and compatibility with solvents and polymers. The results also demonstrated that charge transport between the nanowires was facilitated due to low wire-to-wire junction resistance. To further figure out the charge transport mechanism in organic-inorganic nanocomposites and the potential applications, tellurium nanowires and ferric chloride doped poly (3-hexylthiophene-2,5-diyl)(P3HT) were used to characterize energy band alignment effects on charge transport, electrical conductivity, and thermoelectric properties. The results showed that charge transfer between nanowires can be mediated by the polymer and may potentially increase the electrical conductivity as compared to the pure polymer or pure nanowires; while the observed enhancement of power factor (equal to electrical conductivity times the square of Seebeck coefficient) may not be affected by the energy band alignment. It is important to investigate the change of polymer morphology caused by molecular doping and processing method to determine how the morphology will influence the electrical and thermoelectric properties. Various p-type dopants, including ferric chloride and molybdenum tris(1,2-bis(trifluoromethyl)ethane-1,2-dithiolene) (Motfd3), were examined for us in P3HT and other polymers. The results showed that: i) At light doping levels, the electrical conductivity and power factor of polymers doped with the large electron affinity (EA) dopants were larger than small EA dopants; ii) At heavy doping levels, the large size dopants cannot effectively dope polymers even for the dopants with large EAs; iii) For the same dopant, as the IE of the polymer increased, the doping efficiency gradually decreased.
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Guo, Xugang. "IMIDE-FUNCTIONALIZED CONJUGATED POLYMERS: SYNTHESIS, STRUCTURE-PROPERTY AND DEVICE STUDIES." Lexington, Ky. : [University of Kentucky Libraries], 2009. http://hdl.handle.net/10225/1100.
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Thesis (Ph. D.)--University of Kentucky, 2009.Title from document title page (viewed on October 29, 2009). Document formatted into pages; contains: xvi, 227 p. : ill. (some col.). Includes abstract and vita. Includes bibliographical references (p. 207-224).
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Bheemireddy, Sambasiva Reddy. "SYNTHESIS OF CONJUGATED SMALL MOLECULES AND POLYMERS BY A PALLADIUM CATALYZED CYCLOPENTANNULATION STRATEGY – TOWARDS NEW ORGANIC SEMICONDUCTORS." OpenSIUC, 2017. https://opensiuc.lib.siu.edu/dissertations/1338.
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The utility of conjugated small molecules and polymers as organic semiconductors have seen a tremendous growth in research and development in academia as well as industry because of their processability and flexibility advantages in comparison to inorganic semiconductors. The extensive research over the years has produced a large number of p-type (hole conducting) and n-type (electron conducting) semiconductors that can be used to construct organic electronic devices. Of these materials, p-type semiconductors are more established and extensively studied because of the ease of preparation as well as their better general stability in comparison to n-type materials. Despite recent research into the development of n-type materials, fullerene (C60 and C70) and its derivatives are still the predominant materials used as electron acceptors for OPV applications. By taking advantage of the electron accepting behavior of cyclopenta[hi]aceanthrylene fragment of C70, we have designed and synthesized new materials based on cyclopenta-fused polycyclic aromatic hydrocarbons (CP-PAHs). By using a newly developed palladium catalyzed cyclopentannulation methodology, 1,2,6,7- tetraarylcyclopenta[hi]aceanthrylenes were prepared by treating diarylethynylenes with 9,10-dibromoanthracene. Scholl cyclodehydrogenation was used to close the externally fused aryl groups to provide access to contorted 2,7,13,18- tetraalkoxytetrabenzo[f,h,r,t]rubicenes. The contortion provides access to more soluble materials than their planar counterparts but still ii allows significant pi-pi stacking between molecules. Using a modified palladium catalyzed cyclopentannulation polymerization followed by a cyclodehydrogenation reaction, a nonconventional synthesis of CP-PAH embedded ladder polymers was also achieved. These ladder polymers possess broad UV-Vis absorptions and narrow optical gaps of 1.17-1.29 eV. The synthesis of new donor-acceptor copolymers incorporating electron accepting 1,2,6,7- tetra(4-dodecylphenyl)dicyclopenta[cd,jk]pyrene was also achieved. The donor unit was varied between thiophene, bithiophene, and 1,4-diethynyl-2,5-bis((2-octyldodecyl)oxy)-benzene producing polymers with high molecular weights and considerably low band gaps. This newly developed cyclopentannulation method was also used to synthesize a new class of stabilized pentacene derivatives with externally fused five-membered rings. The target compounds were synthesized via chemical manipulation of a partially saturated 6,13-dibromopentacene precursor that can be fully aromatized in a final step via a DDQ mediated dehydrogenation reaction. Photodegradation studies reveal the new 1,2,8,9-tetraphenyldicyclopenta[fg,qr]pentacene derivatives are more photostable than TIPS-pentacene, and possess narrow optical gaps of ~1.2 eV. Because anthradithophene (ADT) is more stable than pentacene while maintaining good electronic properties, the synthesis of cyclopentannulated anthradithiophenes (CP-ADTs) was also explored. Synthesis of a highly contorted ADT analogue was achieved by treating 5,11-dibromo-anthradithiophene with 3,3’-dimethoxy,1,1’-diphenyl acetylene under palladium catalyzed cyclopentannulation conditions followed by Scholl cyclodehydrogenation.
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Sobczak, Quentin. "Synthesis of new amino-containing π-conjugated polymers via dimerization of acyclic aminoarylcarbenes." Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0208.
Full textAbstract:
Dans cette thèse, la synthèse de polymères semi-conducteurs par une voie originale n’utilisant pas de métaux, afin de les intégrer dans des dispositifs électroniques organiques comme les OLED (Organic light emitting diode) a été developpée. Le but est de développer et d’optimiser une nouvelle méthode de synthèse en s’appuyant sur des bis-aminoarylcarbènes acyclique en tant que blocs constructeurs afin d’obtenir de nouveaux polymères PPV-like. Dans un premier temps, la réaction de dimérisation est étudiée au niveau moléculaire avec la synthèse et caractérisations de diaminoalcènes obtenu à partir de carbènes acycliques monofonctionnels. Le mécanisme et la sélectivité de cette réaction de dimérisation ont également été examiné par voies expérimentales et théoriques. Dans un deuxième temps, la réaction de dimérisation a été étendu au niveau macromoléculaire avec la synthèse et caractérisations de nouveaux PPV-like polymères contenant des fonctions amino en α de la double liaison. Par la suite, l’influence de ces groupements amino sur les propriétés optoélectroniques de ces N-PPV une fois modifiés chimiquement a pu être étudié. Enfin, les caractéristiques particulières des diaminoalcènes synthétisés au cours cette thèse ont permis une étude préliminaire sur leurs applications potentielles en tant que catalyseur organiques dans la réaction de polymérisation radicalaire par transfert d’atomesIn this thesis, the study focuses on the synthesis of semi-conducting polymers by an original pathway free from metals, in order to integrate them into organic electronic devices such as OLEDs (Organic light emitting diodes). The aim is to develop and optimize a new methodology using acyclic bis-aminoarylcarbenes as building blocks to synthesize new PPV-like polymers. First, the dimerization reaction is studied at a molecular level with the synthesis and characterization of diaminoalkenes obtained from monofunctional acyclic aminoarylcarbenes. The mechanism and the selectivity of this dimerization reaction is also investigated experimentally and theoretically. In a second step, the dimerization reaction was extended at a macromolecular level with the synthesis and characterization of new PPV-like polymers containing amino functions in α of the double bond. Subsequently, the influence of these chemically modified amino groups on the optoelectronic properties of these N-PPVs has been studied. Finally, the specific characteristics of the diaminoalkenes synthesized during this thesis has allowed a preliminary study on their potential applications as organocatalysts in the atom transfer radical polymerization reaction