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Kawase, Takeo. "Device structures made with semiconductive conjugated polymers." Thesis, University of Cambridge, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246551.
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Harris, Natalie K. "Gas detection using semiconducting polymers." Thesis, University of Manchester, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262652.
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Root, Samuel E. "Mechanical Properties of Semiconducting Polymers." Thesis, University of California, San Diego, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10745535.
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Mechanical softness and deformability underpin most of the advantages offered by semiconducting polymers. A detailed understanding of the mechanical properties of these materials is crucial for the design and manufacturing of robust, thin-film devices such as solar cells, displays, and sensors. The mechanical behavior of polymers is a complex function of many interrelated factors that span multiple scales, ranging from molecular structure, to microstructural morphology, and device geometry. This thesis builds a comprehensive understanding of the thermomechanical properties of polymeric semiconductors through the development and experimental-validation of computational methods for mechanical simulation. A predictive computational methodology is designed and encapsulated into open-sourced software for automating molecular dynamics simulations on modern supercomputing hardware. These simulations are used to explore the role of molecular structure/weight and processing conditions on solid-state morphology and thermomechanical behavior. Experimental characterization is employed to test these predictions—including the development of simple, new techniques for rigorously characterizing thermal transitions and fracture mechanics of thin films.
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Mills, Christopher Alan. "Investigations into low band-gap, semiconducting polymers." Thesis, Bangor University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340950.
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Gomes, Henrique Leonel. "Fabrication and characterization of electronic devices based on poly(3-methlythiophene)." Thesis, Bangor University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358622.
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Vongsaysy, Uyxing. "Studies on processing additives introduced to increase the efficiency of organic solar cells : selection and mechanistic effects." Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0230/document.
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Les cellules solaires organiques à hétérojonction en volume (BHJ en anglais) font l'objet d'un grand intérêt car elles représentent une source d'énergie bon marché et renouvelable. Cependant, à cause des rendements généralement bas, ce type de cellule peine à intégrer le marché. Afin d’en augmenter le rendement, contrôler la morphologie des semi-conducteurs dans la BHJ représente un élément clé. Dans ce contexte, il apparaît, dans la littérature, que les additifs solvant permettent de contrôler cette morphologie et d'augmenter les rendements.Cette thèse a pour but de fournir une étude complète sur l'utilisation des additifs. Le couple de semi-conducteurs étudié est le poly(3-hexylthiophene) (P3HT)/[6,6]-phényl-C61butanoate de méthyle (PC61BM).Une première partie présente une méthode développée pour guider la sélection d'additifs parmi une liste de solvants. Cette méthode emploie les paramètres de solubilité de Hansen des semi-conducteurs. Elle est appliquée au système P3HT/PC61BM et résulte en l'identification de trois nouveaux additifs performants. Ensuite, des caractérisations structurales, électriques et optiques sont menées sur la BHJ et permettent d'identifier les effets des additifs. Les effets de ces additifs se révèlent être différents en fonction de l'architecture des dispositifs. L'origine de telles différences est corrélée aux variations de mobilités des porteurs de charge causées par les additifs. Des tests de photo-stabilité ont été menés et montrent que les additifs sont capables d'augmenter la stabilité des cellules solaires. L’origine de telles améliorations est étudiée. Enfin, l'étude est étendue à deux autres nouveaux polymères semi-conducteursPolymeric bulk heterojunction (BHJ) organic solar cells (OSCs) have attracted significant interest as a low cost and renewable technology to harvest solar energy. However, their generally low efficiencies are a barrier for their movement into commercial application. Controlling the BHJ morphology is a key step in the pursuit of higher OSC efficiencies. Processing additives have emerged as effective components for optimizing the BHJ morphology. This thesis provides a comprehensive study on the introduction of additives in the formulation of semiconductors. The semiconductor system studied is based on poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PC61 BM). First, a method was developed to guide the selection of additives from a large range of solvents. This method employs the Hansen solubility parameters of the semiconductors and was successfully applied to the P3HT/PC61 BMsystem. It resulted in the identification of three new efficient additives. Next, the mechanistic role of additives in influencing the BHJ morphology is investigated by performing structural, electrical and optical characterizations. Also, the effect of additives on OSC performance was found to depend on the type of the OSC architecture. Such differences were correlated to the variations in charge carrier mobilities caused by the additive. Furthermore, photo-stability tests, performed on different types of OSCs, showed that processing additives can improve the photo-stability. The origin of such improvement is investigated. Finally, the scope of this study is extended to two other donor semiconducting polymers
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Montenegro, Rivelino V. D. "Crystallization, biomimetics and semiconducting polymers in confined systems." Phd thesis, Universität Potsdam, 2003. http://opus.kobv.de/ubp/volltexte/2005/76/.
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populärwissenschaftlicher Abstract:Kristallisation, Biomimetik und halbleitende Polymere in räumlich begrenzten Systemen:
Öl und Wasser mischen sich nicht, man kann aber aus beiden Flüssigkeiten Emulsionen herstellen, bei denen Tröpfchen der einen Flüssigkeit in der anderen Flüssigkeit vorliegen. Das heißt, es können entweder Öltröpfchen in Wasser oder Wassertröpfchen in Öl erzeugt werden. Aus täglichen Erfahrungen, z.B. beim Kochen weiß man jedoch, dass sich eine Emulsion durch Schütteln oder Rühren herstellen lässt, diese jedoch nicht besonders stabil ist. Mit Hilfe von hohen Scherenergien kann man nun sehr kleine, in ihrer Größe sehr einheitliche und außerdem sehr stabile Tröpfchen von 1/10000 mm erhalten. Eine solche Emulsion wird Miniemulsion genannt.
In der Dissertation wurden nun z.B. Miniemulsionen untersucht, die aus kleinen Wassertröpfchen in einem Öl bestehen. Es konnte gezeigt werden, dass das Wasser in diesen Tröpfchen, also in den räumlich begrenzten Systemen, nicht bei 0 °C, sondern bei -22 °C kristallisierte. Wie lässt sich das erklären? Wenn man einen Eimer Wasser hat, dann bildet sich normalerweise bei 0 °C Eis, da nämlich in dem Wasser einige (manchmal ganz wenige) Keime (z.B. Schutzteilchen, ein Fussel etc.) vorhanden sind, an denen sich die ersten Kristalle bilden. Wenn sich dann einmal ein Kristall gebildet hat, kann das Wasser im gesamten Eimer schnell zu Eis werden. Ultrareines Wasser würde bei -22 °C kristallisieren. Wenn man jetzt die Menge Wasser aus dem Eimer in kleine Tröpfchen bringt, dann hat man eine sehr, sehr große Zahl, nämlich 1017 Tröpfchen, in einem Liter Emulsion vorliegen. Die wenigen Schmutzpartikel verteilen auf sehr wenige Tröpfchen, die anderen Tröpfchen sind ultrarein. Daher kristallisieren sie erst bei -22 °C.
Im Rahmen der Arbeit konnte auch gezeigt werden, dass die Miniemulsionen genutzt werden können, um kleine Gelatine-Partikel, also Nanogummibärchen, herzustellen. Diese Nanogummibärchen quellen bei Erhöhung der Temperatur auf ca. 38 °C an. Das kann ausgenutzt werden, um zum Beispiel Medikamente zunächst in den Partikeln im menschlichen Körper zu transportieren, die Medikamente werden dann an einer gewünschten Stelle freigelassen. In der Arbeit wurde auch gezeigt, dass die Gelatine-Partikel genutzt werden können, um die Natur nachzuahnen (Biomimetik). Innerhalb der Partikel kann nämlich gezielt Knochenmaterial aufgebaut werden kann. Die Gelatine-Knochen-Partikel können dazu genutzt werden, um schwer heilende oder komplizierte Knochenbrüche zu beheben. Gelatine wird nämlich nach einigen Tagen abgebaut, das Knochenmaterial kann in den Knochen eingebaut werden.
LEDs werden heute bereits vielfältig verwendet. LEDs bestehen aus Halbleitern, wie z.B. Silizium. Neuerdings werden dazu auch halbleitende Polymere eingesetzt. Das große Problem bei diesen Materialien ist, dass sie aus Lösungsmitteln aufgebracht werden. Im Rahmen der Doktorarbeit wurde gezeigt, dass der Prozess der Miniemulsionen genutzt werden kann, um umweltfreundlich diese LEDs herzustellen. Man stellt dazu nun wässrige Dispersionen mit den Polymerpartikeln her. Damit hat man nicht nur das Lösungsmittel vermieden, das hat nun noch einen weiteren Vorteil: man kann nämlich diese Dispersion auf sehr einfache Art verdrucken, im einfachsten Fall verwendet man einfach einen handelsüblichen Tintenstrahldrucker.
The colloidal systems are present everywhere in many varieties such as emulsions (liquid droplets dispersed in liquid), aerosols (liquid dispersed in gas), foam (gas in liquid), etc. Among several new methods for the preparation of colloids, the so-called miniemulsion technique has been shown to be one of the most promising. Miniemulsions are defined as stable emulsions consisting of droplets with a size of 50-500 nm by shearing a system containing oil, water, a surfactant, and a highly water insoluble compound, the so-called hydrophobe
1. In the first part of this work, dynamic crystallization and melting experiments are described which were performed in small, stable and narrowly distributed nanodroplets (confined systems) of miniemulsions. Both regular and inverse systems were examined, characterizing, first, the crystallization of hexadecane, secondly, the crystallization of ice. It was shown for both cases that the temperature of crystallization in such droplets is significantly decreased (or the required undercooling is increased) as compared to the bulk material. This was attributed to a very effective suppression of heterogeneous nucleation. It was also found that the required undercooling depends on the nanodroplet size: with decreasing droplet size the undercooling increases.
2. It is shown that the temperature of crystallization of other n-alkanes in nanodroplets is also significantly decreased as compared to the bulk material due to a very effective suppression of heterogeneous nucleation. A very different behavior was detected between odd and even alkanes. In even alkanes, the confinement in small droplets changes the crystal structure from a triclinic (as seen in bulk) to an orthorhombic structure, which is attributed to finite size effects inside the droplets. An intermediate metastable rotator phase is of less relevance for the miniemulsion droplets than in the bulk. For odd alkanes, only a strong temperature shift compared to the bulk system is observed, but no structure change. A triclinic structure is formed both in bulk and in miniemulsion droplets.
3. In the next part of the thesis it is shown how miniemulsions could be successfully applied in the development of materials with potential application in pharmaceutical and medical fields. The production of cross-linked gelatin nanoparticles is feasible. Starting from an inverse miniemulsion, the softness of the particles can be controlled by varying the initial concentration, amount of cross-link agent, time of cross-linking, among other parameters. Such particles show a thermo-reversible effect, e.g. the particles swell in water above 37 °C and shrink below this temperature. Above 37 °C the chains loose the physical cross-linking, however the particles do not loose their integrity, because of the chemical cross-linking. Those particles have potential use as drug carriers, since gelatin is a natural polymer derived from collagen.
4. The cross-linked gelatin nanoparticles have been used for the biomineralization of hydroxyapatite (HAP), a biomineral, which is the major constituent of our bones. The biomineralization of HAP crystals within the gelatin nanoparticles results in a hybrid material, which has potential use as a bone repair material.
5. In the last part of this work we have shown that layers of conjugated semiconducting polymers can be deposited from aqueous dispersion prepared by the miniemulsion process. Dispersions of particles of different conjugated semiconducting polymers such as a ladder-type poly(para-phenylene) and several soluble derivatives of polyfluorene could be prepared with well-controlled particle sizes ranging between 70 - 250 nm. Layers of polymer blends were prepared with controlled lateral dimensions of phase separation on sub-micrometer scales, utilizing either a mixture of single component nanoparticles or nanoparticles containing two polymers. From the results of energy transfer it is demonstrated that blending two polymers in the same particle leads to a higher efficiency due to the better contact between the polymers. Such an effect is of great interest for the fabrication of opto-electronic devices such as light emitting diodes with nanometer size emitting points and solar cells comprising of blends of electron donating and electron accepting polymers.
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Linshöft, Julian [Verfasser]. "Main Group Heterocycles for Semiconducting Polymers / Julian Linshöft." Kiel : Universitätsbibliothek Kiel, 2014. http://d-nb.info/106294786X/34.
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Bartlett, Jon G. "Automated gas and odour sensing using semiconducting polymers." Thesis, University of Manchester, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284116.
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Hon, Sherman Siu-Man. "Calcium vapour deposition on semiconducting polymers studied by adsorption calorimetry and visible light absorption." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/863.
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A novel UHV microcalorimeter has been used to study the interaction between
calcium and three polymers: MEH-PPV, MEH-PPP and P3HT. All three polymers
behave differently in their reaction kinetics with calcium. On MEH-PPV we measure
45 μJ/cm² of heat generated in excess of the heat of bulk metal growth, 120 μJ/cm²
for MEH-PPP, and 100 μJ/cm² for P3HT. Comparison of the MEH-PPV and MEHPPP
data indicate that the initial reaction of calcium with MEH-PPV occurs at the
vinylene group. We propose, based on hypothetical models, that calcium reacts with
the vinylene groups of MEH-PPV with a reaction heat of 360 kJ/mol and at a
projected surface density of 1.7 sites/nm², while it reacts with the phenylene groups
of MEH-PPP in a two-step process with reaction heats of 200 and 360 kJ/mol
respectively, at a projected surface density of 3.5 sites/nm².
Optical absorption experiments, using either a 1.85 eV diode laser or a xenon lamp
coupled to a scanning monochromator, have also been performed using the same
calorimeter sensor. In the case of MEH-PPV, using the laser we find an optical
absorption cross-section of 3E-¹⁷ cm² per incident calcium atom at low coverages.
The change in absorptance at higher coverages correlates perfectly with the
population of reacted Ca atoms determined calorimetrically. The size of the
absorbance cross-section, and its position just within the band gap of the polymer, are
consistent with the reaction being one of polaron formation. Calcium does not appear
to dope P3HT, while the photon energy range of 1.5 to 3.75 eV used in these
experiments is likely too small for probing polaronic energy states in MEH-PPP.
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Intaniwet, Akarin. "Semiconducting polymers for real time direct X-ray detection." Thesis, University of Surrey, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.538028.
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Existing inorganic materials for radiation dosimeters suffer from several drawbacks, including their inability to cover large curved areas, lack of tissueequivalence, toxicity, and mechanical inflexibility. As an alternative to inorganics, poly(triarylamine) (PTAA)-based devices have been evaluated for their suitability for detecting radiation via the direct creation of X-ray induced photocurrents. The device was prepared by sandwiching an active layer of PT AA between a transparent indium tin oxide (ITO) b()ttom contact and a metal top contact. The charge transport properties of the device were assessed using the spectral photo current method. Increased photocurrent sensitivity was observed for samples annealed at 150°C, consistent with solvent loss, which was confirmed by thermogravimetric analysis. A diode with an Al contact shows the highest quality of recti tying junction, and it produces a high X-ray photocurrent (several nA) that is stable during continuous exposure to 50 kV Mo Ka X-radiation over long timescales, combined with a high signal-to-noise ratio with fast response times of less than 0.25 s. To optimize the performance of the device, the X-ray stopping power and the charge carrier mobility of the active layer have been modified by the introduction of various concentrations of the high atomic number bismuth oxide nanoparticles and the high mobility TIPS-pentacene organic material, respectively. The increasing of the devices' sensitivity correlates with an increased charge carrier mobility which was measured by a time-of-flight photocurrent measurement. Good stability of Xray sensitivity was found as the dosimeter was exposed to the X-ray beam for a long period of time with no discernible reduction in performance. These results indicate that PTAA is a highly-promising material for the direct detection of X-rays and potentially other types of radiation.
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Peng, Yi-Hsing. "Study of transient effects in photo-excited semiconducting polymers." College Park, Md.: University of Maryland, 2008. http://hdl.handle.net/1903/8801.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2008.Thesis research directed by: Dept. of Electrical and Computer Engineering E. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Bannock, James Henry. "Controlled synthesis of semiconducting polymers in droplet flow microreactors." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/45405.
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This thesis reports the development of droplet flow reactors for the preparation of semiconducting polymers, focussing specifically on poly(3-hexylthiophene) (P3HT) pre- pared by Grignard metathesis polymerisation, and random copolymers of P3HT with poly(3-hexylselenophene) (P3HS). In contrast to conventional continuous flow reactors (where the flow consists of a single solvent phase), droplet reactors incorporate an immiscible ’carrier fluid’ that divides the solvent phase into a stream of near-identical microlitre-sized droplets which then pass through the reactor sequentially. In this way, the solvent phase is confined to a well-defined volume that no longer makes contact with the surrounding reactor architecture, and thereby overcomes blockage problems associated with preparation of polymers in continuous flow reactors. To overcome the limited solubility of the Ni(dppp)Cl2 catalyst widely used in Grignard metathesis polymerisation, a more soluble derivative, Ni(dppp)Br2, has been prepared. This catalyst allows P3HT to be synthesised with accurate control over a wide range of molecular weights, even at high throughput (up to 1 kg/day). A scalable ’tube-in-shell’ reactor was developed to provide improved thermal uniformity along the flow reac- tor, enabling the preparation of high molecular weight P3HT with Mw up to 190 kg/mol (PDI 1.5) and lower weight polymers with narrow polydispersity (PDI 1.1). To facilitate multistep chemistries in droplets, a new three-phase methodology is presented that enables the controlled addition of reagents downstream of the original droplet gener- ation. With a view to applying P3HT in electronic devices, an investigation into the influ- ence of polymer purity on the efficiency of P3HT:fullerene bulk heterojunction devices is reported. Polymer purity is shown to have a strong influence over polymer solubility and final device efficiency. With the purest polymers, efficiencies of up to 5.0 % and 7.0 % were obtained with PC60BM and IC60BA, respectively (PC60BM: phenyl-C61-butyric acid methyl ester, IC60BA: indene-C60 bis-adduct). The thesis finishes with the development of a new style of liquid-liquid separator, a key tool for post-processing droplet flows and enabling sequential operations.
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Lafalce, Evan. "Photophysical and Electronic Properties of Low-Bandgap Semiconducting Polymers." Scholar Commons, 2014. https://scholarcommons.usf.edu/etd/5424.
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In this Ph.D. work, we investigate the optoelectronic properties of low-bandgap semiconducting polymers and project the potential for employing these materials in electronic and photonics devices, with a particular emphasis on use in organic solar cells. The field of organic solar cells is well developed and many of the fundamental aspects of device operation and material requirements have been established. However, there is still more work to be done in order for these devices to ultimately reach their full potential and achieve commercialization. Of immediate concern is the low power conversion efficiency demonstrated in these devices so far. In order to improve upon this efficiency, several routes are being explored. Because the optical bandgaps of semiconducting polymers are larger than in inorganic semiconductors, one of the most promising routes currently under exploration is the development of low-bandgap materials. Using polymers with lower band gaps will allow more of the solar irradiance spectrum to be absorbed and converted into electricity and thus possibly boost the overall efficiency.
The bandgap of these semiconducting polymers is determined by the chemical structure, and therefore can be tailored through synthesis if the relevant structure-property relationships are well-understood. The materials studied in this work, a new series of Poly(thienylenevinylene) (PTV) derivatives, posses lower band gaps than conventional polymers through a design that incorporates aromatic-quinoid structural disturbances. This type of chemical structure delocalizes the electronic structure along the polymer backbone and reduces the energy of the lowest excited-state leading to a smaller band-gap. We investigate these materials through a variety of techniques including linear spectroscopy such as absorption and photoluminescence, pump-probe techniques like cw-photoinduced absorption and transient photo-induced absorption, and the non-linear electroasborption technique in order to interrogate the consequences of the delocalized electronic structure and its response to optical stimuli. We additionally consider the effects of environmental factors such as temperature, solvents and chemical doping agents. During the course of these investigations, we consider both of the two primary categorical descriptions of structure-property relationships for polymers within the molecular exciton model, namely the role of inter-molecular interactions on the electronic properties through the variation of supermolecular order and the fundamental determination of electronic structure due to specific intra-molecular interaction along the backbone of the polymer chain. We show that the dilution of aromaticity in semiconducting polymers, while being a viable means of reducing the optical band gap, results in a significant increase in the role of electron-electron interactions in determining the electronic properties. This is observed to be detrimental for device performance as the highly polarizable excited state common to polymers gives way to highly correlated state that extinguishes both the emissive properties and more importantly for solar cells, the charge-generating characteristics. This situation is shown to be predominant regardless of the nature of interchain interactions. We therefore show that the method of obtaining low-bandgap polymers here comes along with costly side-effects that inhibit their efficient application in solar cells.
Further, we directly probe the efficacy of these materials in the common bulk-heterojunction architecture with both spectroscopy and device characterization in order to determine the limiting and beneficial factors. We show that, while from the point of view of absorption of solar radiation these low-bandgap polymers are more suited for solar cells, the ability to convert the absorbed photons into electron-hole pairs and generate electricity is lacking, due to the internal conversion into the highly correlated state and thus, the absorbed photon energy is lost. For completeness, we fabricate devices and verify that both the charge-transport properties and alignment of charge extraction levels with those of the contacts can not be responsible for the dramatic decrease in efficiency found from these devices as compared to other higher band gap polymers. We thus conclusively determine that the lack of power converison efficiency is governed by the inefficiency of charge-generation resulting from the intrinsic defective molecular structures rendering a low-lying optically forbidden state below the lowest optical allowed state that consumes the majority of the photogenerated excitons.
It is emphasized that our means of investigation allow us to truly access the potential of these materials. In contrast, the direct application of these systems in devices and interpretation of the performance is exceedingly complex and may obscure their true potential. In other words, poor performance from a device may be extrinsic in nature and the optimization process may be very costly with respect to both time and materials. The methods used here however, allow us to determine the intrinsic potential. Not only is this beneficial in terms of preserving the resources that would be used on the trial-and-error method for devices, but it also allows us to learn more on a fundamental level about the structure-property relationships and their implications for device performance. The benefits of this increased understanding are two-fold. First, by learning about the fundamental response of a material, a new application may be realized. For example, the rapidly efficient internal conversion process that renders the materials in this study as poor candidates for solar cells may make them useful for photonics applications, as optical switches, for instance. Secondly, this type of investigation has implications for the whole organic electronics community instead of just being limited to the particular material system and the primary application attempted. In this case, we are essentially able to determine a threshold for aromaticty necessary in a structure that will preserve the stability of the ionic excited state that is useful for charge generation in solar cells.
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Ferguson, John B. "Transport studies of conducting, semiconducting and photoconducting star polymers." The Ohio State University, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=osu1343144440.
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Donaghey, Jenny E. "Synthesis of semiconducting polymers for use in organic electronics." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/9827.
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A series of novel semiconducting co-polymers based on known, fused aromatic monomers (dibenzosilole, dithienosilole and dithienopyrrole) were synthesized for use in organic field effect transistor (OFET) devices. The fused monomers were copolymerized with triarylamine and thienothiophene units to give a series of six donor polymers. Their electronic energy levels were probed by UV-Vis and photoelectron spectroscopy, and predictions regarding their performance were drawn from this information. Two polymers were tested in OFETs and conclusions were made concerning the relationship between structure and performance. Four donor-acceptor type polymers were synthesized using dithienopyrrole as the electron rich unit. This monomer was copolymerized with benzothiadiazole, difluorobenzothiadiazole, thienopyrrolodione and 1,1’-bithienopyrrolodione. These low band gap polymers were tested as the donor polymer in polymer:fullerene BHJ devices. A novel monomer with long branched alkyl substituents, based on the extended fused-ring system indacenodithiophene (IDT), was synthesized. The nitrogen analogue of this monomer (NIDT) was of interest as its performance could be compared to the carbon and silicon versions of IDT. A route to NIDT was devised and then it was polymerized with four electron poor monomers. The energy levels were estimated by UV-Vis and photoelectron spectroscopy, followed by testing of the materials in OFET and OPV devices. Those with the lowest lying HOMO levels performed best in OPVs. Another series of NIDT containing polymers were synthesized, designed specifically for use in OFET devices. The aim was to produce polymers with highly planar backbones which would form ordered domains and enhance hole transport. An NIDT monomer was synthesized with linear hexadecyl substituents in order to improve π-stacking. The linear NIDT monomer was then copolymerized with thiophene, thienothiophene, thienopyrrolodione and diketopyrrolopyrrole. It was found that the diketopyrrolopyrrole containing polymer, performed best in OFETs and the molecular weight played a large role in how a polymer performed.
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Vu, Quoc Trung. "Electrophoretic deposition of semiconducting polymer metal oxide nanocomposites and characterization of the resulting films." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2005. http://nbn-resolving.de/urn:nbn:de:swb:14-1137420064480-98497.
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Conducting polymer nanocomposites composed of metal oxides and polythiophene was synthesized by chemical polymerization in colloidal suspensions. The electrochemical and photoelectrochemical properties of such nanocomposites have been studied. For these investigations films of nanocomposites were prepared by an electrophoretic deposition process. The deposition process was studied in greater detail and kinetic details were determined. The high voltage electrophoretic deposition process was combined with a quartz crystal microbalance (QCM). Then the films were characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and photocurrent spectroscopy.
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Burroughes, Jeremy Henley. "The physical processes in organic semiconducting polymer devices." Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306360.
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Kim, Youngkyoo. "Organic solar cells based on highly self-organizing semiconducting polymers." Thesis, Imperial College London, 2006. http://hdl.handle.net/10044/1/49917.
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In this thesis I have studied organic solar cells (photovoltaic devices) based on a highly self-organizing polymer, regioregular poly(3-hexyIthiophene) (P3HT), because of its particular crystallization tendency leading to high charge carrier mobilities, good light-harvesting in red parts, and suitable energy band structure for an electron-donor. Prior to organic solar cell study, the pristine P3HT films have been investigated to understand their optical/electrical property and nanocrystal structure changes upon thermal annealing. As an electron-acceptor for organic solar cells, two candidates were employed: One is polymer [poly(poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT)), another is big small molecule [[6,6]-phenyl Cgi-butyric acid methyl ester (PCBM)]. The kinds of blends used for organic solar cell fabrication were P3HT:F8BT, P3HT:PCBM, and P3HT:PCBM:F8BT. Organic solar cells were fabricated by spin-coating these blend films onto transparent conductive oxide coated substrates followed by depositing metal electrodes (sometimes inserting LiF). For better understanding of device performance changes, blend films have been examined with optical absorption, photoluminescence including time-resloved system, normal reflection mode x-ray diffraction, grazing incidence x-ray diffraction (Synchrotron), atomic force microscopy, scanning electron microscopy, high resolution transmission electron microscopy with field emission gun, transient absorption spectroscopy, and time-of-flight mobility measurement. As a result, P3HT:F8BT solar cells (maximum external quantum efficiency=~3%) showed poorer efficiency than P3HT:PCBM solar cells (maximum external quantum efficiency=~73%), though both blends have P3HT components, which is attributed to the low electron mobility of F8BT compared to PCBM. The power conversion efficiency of P3HT:PCBM solar cells has reached 4.4-5.5% at 85~8.5mW/cm^ (air mass 1.5 simulated solar illumination), which is ascribed mainly to the formation of vertical phase segregation upon thermal annealing leading to pseudo layered p-n junction. This layered structure might reduce the charge recombination between P3HT positive polaron (radical cation) and PCBM negative polaron (radical anion), a parameter that has been quantitatively analysed using a new model proposed in this work.
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Beatrup, Daniel. "Electrochemical studies of semiconducting polymers : correlation of energetics and stability." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/44963.
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In order to make organic solar cells commercially viable, it is necessary to design devices with higher efficiency and longer lifetimes than is currently accessible. Energetics of materials used in organic solar cells are already known to play a key role in various aspects of device performance, including charge generation and ambient stability. In order to make progress on either of these fronts, a clear understanding of frontier molecular orbital energy levels in semiconducting polymers is key, which is one issue that this thesis aims to address. Less understood is what role energetics plays in operational stability, which is another issue that this thesis aims to address. Cyclic voltammetry (CV) was employed to study the effect of relative semiconducting polymer crystallinity on highest occupied molecular orbital (HOMO) energy levels in neat films. Two HOMO energy levels were found, with a difference in energy of ca 60 meV, corresponding to relatively ordered and disordered phases in the film. The effect of various thermal treatments on the relative ratio of ordered:disordered phases is investigated. During solar cell operation, the semiconducting polymers are partially oxidised, with bulk hole polaron densities of ca 10^15-17 cm-3. Chronoamperometry and absorption spectroscopy were combined to develop a methodology for accelerating degradation caused by the presence of hole polarons in neat films. The methodology was initially employed to investigate the relative stabilities of the hole polarons formed when P3HT and two structurally analogous semiconducting polymers with deeper HOMO energy levels are partially oxidised. The study was extended to include a variety of donor- acceptor polymers. It is shown that stabilising the HOMO results in a less stable hole polaron.
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Karpov, Yevhen. "Solution Processable Conducting Films based on Doped Polymers:." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-230794.
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Heliotis, George. "Semiconducting polymer gain medi for optical amplifiers and lasers." Thesis, Imperial College London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.407928.
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Hashim, Zeina. "Semiconducting polymer nanospheres : organic alternatives to inorganic quantum dots?" Thesis, King's College London (University of London), 2013. https://kclpure.kcl.ac.uk/portal/en/theses/semiconducting-polymer-nanospheres(c39fdbe6-f281-4472-94aa-d8e44f834b2e).html.
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Semiconducting polymer nanospheres are organic conjugated polymer nanoparticles which are synthesized from benign materials and exhibit excellent fluorescence properties. The nanoparticles are generally larger than inorganic quantum dots with a relatively broad size distribution. Quantum dots, on the other hand, which have extensively been developed and synthesized with precise and narrow distributions of a few nanometers in dimensions, are now being widely investigated as bio-imaging agents, despite the rising concerns about their toxic compositions. Therefore, advances in the synthesis of the organic nanoparticles and investigations into their suitability as alternatives to quantum dots need to be explored. The ‘size problem’ of semiconducting polymer nanospheres – polymer particles are significantly larger than quantum dots – was first tackled in this work. With modifications to the miniemulsion-evaporation synthesis method, narrowly distributed quantum dot-sized nanoparticles with diameters as small as 2 nm were synthesized. These organic nanoparticles which were capped/entwined with poly(ethylene) glycol (PEG), a Food and Drug Administration (FDA) approved surfactant, were found to conserve most of the optical properties of their constituent polymers, and are therefore expected to be useful in bio-imaging applications similar to their larger counterparts. A second nanoparticle system with a dual-modality was then prepared; semiconducting polymer nanospheres capped/entwined with three amphiphilic lipids one of which was gadolinium – diethylene triamine pentacetate, a Magnetic Resonance Imaging (MRI) active ligand. These bimodal nanoparticles also maintained their optical properties, were readily taken up by two cell lines, were distinguishable from the auto-fluorescence of animal tissue, and were found to be MRI-active as revealed by their MRI relaxivity measurements. Finally, the optimized organic nanoparticles and similarly coated quantum dots were investigated for their potential to interact with human blood components, a physiological system which may be very relevant for semiconducting polymer nanospheres used as medical diagnostic agents. The preliminary ex-vivo studies performed revealed that similarly coated organic nanoparticles and quantum dots did not induce platelet aggregation or alter aggregation behaviour in response to a physiological agonist. Further, no evidence of platelet activation, neutrophil activation or increases in platelet-monocyte adhesion was observed. This implied that introduction of the nanoparticles to the blood stream at the concentrations tested may not elicit acute pro-inflammatory effects or alter normal coagulation pathways, although further rigorous evaluation in this area is still required. Fluorescence imaging showed that the organic nanoparticles were taken up by different blood cells and also showed some evidence of adhesion to their surfaces, a property which might find an application in the future. Ultimately, more short-term and long-term safety studies (in-vitro, ex-vitro, and in-vivo) must be conducted before deriving any further conclusions.
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Schüttfort, Torben. "Establishing structure : performance relationships in semiconducting polymer field effect transistors." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610866.
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Saprigin, Alexey V. "Optical studies of conducting polymers in metallic and semiconducting doped states." The Ohio State University, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=osu1343234466.
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Al-Dmour, Hmoud. "Solar cells based on the nc-TiOâ‚‚ semiconducting polymer heterojunction." Thesis, Bangor University, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.445094.
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Sisk, David Theodore. "I. Tunable Luminescence in Dendronized Poly(phenyleneethynylene)s Through Post-Polymerization Chemical Modification II. Rigid, Helical Polymers Based Upon Chiral Hydrobenzoin." Diss., The University of Arizona, 2007. http://hdl.handle.net/10150/194768.
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Dendritic encapsulation of poly(phenyleneethynylene)s or PPEs has been shown to enhance photoluminescent quantum efficiency and facilitate energy transfer by funneling photonic energy absorbed on the dendron periphery efficiently to the conjugated polymeric core. The research presented herein focuses on incorporating degradable dendron onto PPEs, examining whether or not similar benefits were conferred upon the proposed system and controlling polymer luminescence through the elimination of the insulating macromolecules. PPEs appended with disassembling dendrons of various generation sizes were synthesized and their optical properties studied. Polymer luminescence was then quenched via chemical degradation of the disassembling dendrons. Furthermore, the macromolecules resulting from disassembly exhibited tunable luminescence properties upon manipulation of pH. Consequently, it was determined that polymer luminescence could be controlled upon forming phenolic moieties along the PPE backbone. Tunable emission was later realized in the thin film as well through the integration of crosslinkable dendrons onto the polymer core.Recently, helical synthetic linear polymers have demonstrated the ability to facilitate stereoselective processes such as catalysis, recognition and separation. Consequently, it has become increasingly desirable to develop new platforms capable of imparting asymmetry. The work presented herein describes the synthesis of a series of polymers based upon chiral hydrobenzoin and the subsequent conformational analysis performed on these materials. It was envisioned that these polymeric materials might inherently possess conformational asymmetry and as result could be able to impart configurationally chirality by introducing a diastereomeric bias for the formation of one enantiomer over the other during the course of the reaction.
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Carroli, Marco. "Novel materials for direct X-ray detectors based on semiconducting organic polymers." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/9345/.
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Conventional inorganic materials for x-ray radiation sensors suffer from several drawbacks, including their inability to cover large curved areas, me- chanical sti ffness, lack of tissue-equivalence and toxicity. Semiconducting organic polymers represent an alternative and have been employed as di- rect photoconversion material in organic diodes. In contrast to inorganic detector materials, polymers allow low-cost and large area fabrication by sol- vent based methods. In addition their processing is compliant with fexible low-temperature substrates. Flexible and large-area detectors are needed for dosimetry in medical radiotherapy and security applications. The objective of my thesis is to achieve optimized organic polymer diodes for fexible, di- rect x-ray detectors. To this end polymer diodes based on two different semi- conducting polymers, polyvinylcarbazole (PVK) and poly(9,9-dioctyluorene) (PFO) have been fabricated. The diodes show state-of-the-art rectifying be- haviour and hole transport mobilities comparable to reference materials. In order to improve the X-ray stopping power, high-Z nanoparticle Bi2O3 or WO3 where added to realize a polymer-nanoparticle composite with opti- mized properities. X-ray detector characterization resulted in sensitivties of up to 14 uC/Gy/cm2 for PVK when diodes were operated in reverse. Addition of nanoparticles could further improve the performance and a maximum sensitivy of 19 uC/Gy/cm2 was obtained for the PFO diodes. Compared to the pure PFO diode this corresponds to a five-fold increase and thus highlights the potentiality of nanoparticles for polymer detector design. In- terestingly the pure polymer diodes showed an order of magnitude increase in sensitivity when operated in forward regime. The increase was attributed to a different detection mechanism based on the modulation of the diodes conductivity.
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Nunes, Domschke Tamara. "P-doped semiconducting polymers : process optimization, characterization and investigation of air stability." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSES020.
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Les semi-conducteurs organiques (OSCs) sont des matériaux prometteurs pour la production à faible coût de dispositifs électroniques imprimés flexibles et de grandes surfaces. Dans ce contexte, le dopage moléculaire permet de contrôler les propriétés électriques des OSC, offrant un outil puissant pour améliorer les performances de différents dispositifs électroniques. Malgré les progrès dans la compréhension fondamentale du mécanisme de dopage et de leurs procédés, la stabilité des OSC dopés p ont reçu peu d'attention. Or, la stabilité de l'état dopé p en présence d'oxygène et d'humidité est un facteur crucial pour l'intégration de couches dopées dans des dispositifs organiques.Dans cette thèse, nous avons étudié le dopage moléculaire de semi-conducteurs polymères désordonnés et la stabilité du dopage p en présence d'oxygène et d'espèces liées à l'eau. PBDTTT-c et RRa-P3HT ont été utilisés comme matrice de polymères et F4TCNQ et Mo(tfd-COCF3)3 comme dopants de type p. Les paramètres du procédé de dopage ont été soigneusement étudiés pour obtenir un dopage contrôlé et optimiser les propriétés électriques. L'impact de la concentration de dopant a été étudié en termes de propriétés électriques (conductivité), optiques (UV-Vis-NIR) et structurelles (GIWAXS).La stabilité de l'état dopé p a été analysée en surveillant l'évolution des signatures de dopage sous trois atmosphères différentes : l'argon, l'air anhydre et l'air ambiant. Des analyses XPS ont été effectuées pour étudier l'impact de l'exposition à l'air sur l'état chimique des couches dopées p. Des simulations ont été utilisées pour étayer nos résultats.Les résultats actuels ont mis en évidence la présence d'un mécanisme de dédopage important pour les polymères semi-conducteurs dopés-p en présence d'espèces liées à l'eauOrganic semiconductors (OSCs) are promising materials for low-cost, flexible, large-area production of printed electronic devices. In this context, molecular doping allows controlling the electrical properties of OSCs, offering a powerful tool to improve the performances of different electronic devices. Despite the progress in the fundamental understanding of the doping mechanism and processing techniques, stability aspects of p-doped OSCs have received little attention. Nevertheless, the stability of the p-doped state in the presence of oxygen and humidity is a crucial factor to be investigated for the integration of doped layers in organic devices.In this thesis, we have studied the molecular doping of disordered polymer semiconductors and the stability of the p-doped state in the presence of oxygen and water-related species. PBDTTT-c and RRa-P3HT were used as polymer hosts and F4TCNQ and Mo(tfd-COCF3)3 as p-dopants. The process conditions have been carefully studied to achieve controlled doping and to optimize the electrical properties. The impact of the dopant concentration was investigated in terms of electrical (conductivity), optical (UV-Vis-NIR) and structural (GIWAXS) properties of doped layers.The stability of the p-doped state was investigated by monitoring the evolution of the doping signatures under three different atmospheres: argon, anhydrous air, and ambient air. XPS analyses were carried out to investigate the impact of air exposure on the chemical state of p-doped layers. Simulations have been used to support our findings.Present results highlighted the presence of an important dedoping mechanism for p-doped semiconducting polymers in the presence of water-related species
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Chan, Ka Hin. "Charge injection and transport characterization of semiconducting polymers and their bulk heterojunction blends." HKBU Institutional Repository, 2012. https://repository.hkbu.edu.hk/etd_ra/1405.
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Hamelinck, Paul Johan. "Functional surface-initiated polymers : device applications and polymerization techniques." Thesis, University of Cambridge, 2008. https://www.repository.cam.ac.uk/handle/1810/270327.
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Self-assembled monolayers and surface-initiated polymer, or polymer brushes, have attracted attention as they form dense layers with much higher structural order than bulk or solution polymers. Another field of research which has emerged over the last two decades is the field of organic and polymer electronics. In this field molecular order and surface modification are of major influence on the device performance, hence that both self-assembled monolayers as polymer brushes have been investigated to find applications in organic electronic devices. After an introduction into the field self-assembled monolayers, polymer brushes and organic electronics, the first part of this thesis focusses on three applications of surface modification techniques for applications in devices. Alignment of the active material is crucial for high mobilities in organic electronics. Chapter 2 discusses the synthesis of a liquid crystalline surface-initiated polymer and its application to induce strong homeotropic alignment. The alignment is homogeneous over large areas and can be patterned by combining the polymerization with soft lithographic techniques. Mobilities of organic electronic materials can also be strongly influenced by dopants in the material. In field-effect transistors the positioning of the dopant is thought to be crucial, as the conductance predominantly takes place in only a small channel near the dielectric interface. In chapter 3 dopant functionalized monolayers and polymer brushes are presented which enable the localized deposition of dopants in the channel of organic transistors. It is shown that the mobility of charges and hence the device performance is affected by the introduction of this dopant layer. Polymer brushes have been suggested for the fabrication of highly ordered semiconducting polymers. In chapter 4 the use of a thiophene functionalized polymer brush is shown, that can be used as a template for the subsequent growth of highly conjugated surface grafted polythiophene layers. Thick polythiophene layers are obtained, that are low in roughness and show photoluminescence and polychromism upon doping. The second part (chapter 5 and 6) of this thesis presents new techniques for surface polymerizations. It is attractive to investigate reduction of reactor volume for polymer brush growth. Chapter 5 discusses a method to achieve volume reduction by back-filling the superfluous volume with beads. It is found that this influences the polymerization kinetics significantly. The combined advantages of less volume and enhanced reaction speeds enable reduction of the total amount of monomer needed by up to 90%. Chapter 6 presents a controlled way to convert initiators for atom transfer radical polymerization into initiators for nitroxide mediated polymerization. In this way mixed polymer brushes and block co-polymer brushes become accessible. This combination makes it an attractive tool to fabricate complex polymer architectures. The technologies used in this thesis show that the synthesis of polymer brushes enable the fabrication of complex architectures without the wastes normally associated with surface-initiated polymers. Combined with several functionalized polymer brushes with properties that enhance order, influence mobility or serve as template for the growth of surface attached conjugated polymers this shows the high potential for the application of surface-initiated polymers in organic electronics.
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Borrelli, David Christopher. "Oxidative chemical vapor deposition of semiconducting polymers and their use In organic photovoltaics." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/91057.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references.
Organic photovoltaics (OPVs) have received significant interest for their potential low cost, high mechanical flexibility, and unique functionalities. OPVs employing semiconducting polymers in the photoactive layer have traditionally been fabricated almost exclusively with solution-based techniques due to a lack of suitable alternatives. This has thus limited polymer solar cells and other polymer electronic devices to using polymers that are soluble. Here we explore the use of oxidative chemical vapor deposition (oCVD), a vacuum-based method, for the deposition of semiconducting polymers. Polymer deposition by oCVD occurs at moderate vacuum (~0.1 Torr) and low temperature (25 - 150°C). oCVD offers the well-cited processing benefits of vacuum processing, including parallel and sequential deposition, well-defined thickness control and uniformity, and inline integration with other standard vacuum processes (e.g. vacuum thermal evaporation). Various semiconducting polymers, including insoluble polymers that are difficult to process using conventional methods, are successfully deposited via oCVD by changing the monomer precursor. The optoelectronic properties of unsubstituted polyisothianaphthene (PITN) and unsubstituted polythiophene (PT) are first investigated under various oCVD deposition conditions. Higher stage temperatures are shown to increase conjugation in PITN films, resulting in a significant red-shift in the absorption spectrum and a decrease in the optical bandgap from 1.14 to 1.05 eV. The effects of oCVD chamber pressure on the properties of PT are then investigated. Higher chamber pressures are found to correlate with greater conjugation, increased absorption, and larger field effect mobilities in PT films. oCVD PT films are then successfully integrated into planar heterojunction OPVs as the electron donor layer, achieving power conversion efficiencies up to 0.8%. Several alternative device architectures are investigated as means to improve OPV device performance. Promisingly, a ternary energy cascade device architecture is shown to more than double the OPV device performance to over 2%.
by David Christopher Borrelli.
Ph. D.
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Jeon, Taewoo. "Nanostructured hybrid solar cells based on PECVD grown SiNWs and organic semiconducting polymers." Palaiseau, Ecole polytechnique, 2013. http://pastel.archives-ouvertes.fr/docs/00/91/78/26/PDF/Thesis_Taewoo_JEON_EP_PICM.pdf.
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Les cellules photovoltaiques proposent une solution au problème énergétique en raison de leur source inépuisable: le soleil. Plusieurs types de cellules, qu'elle soient inorganiques ou organiques, sont étudiées, avec comme objectif d'obtenir de hauts rendements pour de faibles coûts. Dans ce contexte, ce travail de thèse se propose d'étudier des cellules solaires hybrides nanostructurées à base de nanofils de silicium et de matériaux organiques afin de bénéficier des avantages de ces différents matériaux. La morphologie controlée de la croissance des nanofils de silicium par dépôt chimique en phase vapeur assisté par plasma (PECVD) via un procédé Vapeur-Liquide-Solide est présentée. Le mélange de matériaux organiques est ensuite déposé sur les nanofils de silicium par un procédé d'enduction par centrifugation. Dans ce type de cellules hybrides, les nanofils de silicium jouent le rôles de matériaux accepteurs ou aident à l'absorption de la lumière. Pour améliorer les performance de ces cellules, il est nécessaire d'optimiser la qualité du réseau de nanofils par une gravure chimique visant à éliminer les traces de catalyseur résiduelles ainsi que l'oxyde natif du silicium. Cet effet de la gravure a été largement étudié et discuté. De plus les propriétés d'accepteur d'électrons des nanofils de silicium à base de catalyseurs de Bismuth ont été étudiées. Les résultats montrent clairement le potentiel de ce type de cellules, notamment 1) l'augmentation de la conversion de lumière par l'amélioration de l'efficacité du rendement quantique pour les grandes longueurs d'onde, 2) l'utilisation d'une grande variété de nanofils avec des morphologies et propriétés électriques finement controléesSolar cells are an exciting alternative energy technology due to the infinite energy source, the Sun. Many types of solar cells based on inorganic or organic materials are currently developed with the objective of higher efficiency and lower cost. In this context, this thesis suggests to study nano-structured hybrid solar cells based on silicon nanowires (SiNWs) and organic active materials to benefit advantages of both materials. SiNWs are grown by PECVD on transparent conducting oxide via Vapor-Liquid-Solid (VLS) mechanism with careful control of their nano-morphology. The organic materials made of polymers or blend polymers are then deposited by spin-coating on top of SiNWs. In these hybrid solar cells the SiNWs are used as light-trapping medium and/or electron acceptor material. For better solar cell performance, the optimization of SiNWs array is carried out by removing residual catalyst and etching parasitic hydrogenated amorphous silicon. Their effects on hybrid solar cells have been fully analyzed and discussed. Furthermore, the electron-acceptor properties of the nano-structured SiNWs have been estimated with Bismuth-doped n-type SiNWs. The results clearly reveal the potential of this type of hybrid solar cells, namely, 1) power conversion efficiency improvement by enhancing external quantum efficiency in longer wavelength regime and 2) variety uses of SiNWs by tuning their electrical property and morphology
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Yin, Wei. "Interlayer structure and morphology study of semiconducting polymer thin film devices." Thesis, Loughborough University, 2012. https://dspace.lboro.ac.uk/2134/10041.
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Semiconductors are now the foundation of modern electronic devices, like mobile phones, computers, etc, which are becoming an indispensable part of people s daily life. Polymeric materials are fast developing to be a promising candidate for the manufacturing of semiconducting devices. They have numbers of advantages like flexibility, light weight, low cost, etc, over the conventional silicon option. Similar to metal alloys or composite, use of blends of polymers in organic devices is feasible to modify the product properties, sometimes even possessing new features which not present in either component. The electronic properties of semiconducting polymeric materials have been extensively studied, and well understood. However the physical structure in such devices is more difficult to investigate and thus less well understood. Since blends of polymers are becoming a common option in manufacturing the devices, it is important to gain more understanding of the devices physics. In this work, the interface structure and morphology changes in bilayer systems consisting semiconducting polymers and ordinary polymers have been studied. The literature survey chapter introduces the origin of conjugated polymers and the photovoltaic related properties of semiconducting polymers are also introduced. The development of semiconducting polymer applications, light emitting diodes, solar cells and field effect transistors, is reviewed. Fundamental knowledge of polymer physics, and its relation to the thin film devices are introduced. The results part consists of three chapters. The first chapter is a report of a neutron reflectivity study on bilayer devices containing poly(2,7-(9,9)-di-n-octylfluorene)-alt-(1,4-phenylene-((4-sec-butylphenyl)imino)-1,4-phenylene))(TFB). Neutron data analysis revealed unexpected mixing at the interface between two immiscible polymer layers, forming an insoluble layer after thermal annealing and solvent rinsing. This layer has been found to improve the device performance according to Cambridge Display Technology Ltd. The fitting also indicated phase segregation in the poly(styrene sulfonate)/poly(ethyl dioxy thiophene) (PSS/PEDOT) blend polymer layer might be occurring. The second results chapter is an investigation on bilayer polymer thin film systems including poly(styrene sulfonate)(PSS) and polystyrene(PS) or poly(methyl methacrylate)(PMMA). Similar thermal treatment as on the TFB based system was applied on these bilayer systems. Vibration spectroscopy, surface morphology and device structure characterisations were applied to the system following the treatment process. Evidence of a new insoluble layer formation was reported for PMMA/PSS system. The final results chapter is about the study on polythiophene (PT)/polyethylene (PE) thin film devices. Samples included pure polymer and blends with different weight ratio. Neutron reflectivity measurements were taken at ISIS, Oxford. Results didn t give good specular data, indicating a rough sample surface. Reflective optical microscopy study showed non-homogeneous mixing in the PT/PE blend samples, with clear phase separation observed. Thermal treatment was applied to all samples, and the microscopy images taken afterwards showed limited differences with the pre-annealed ones.
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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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Polanco, Olsen Maria Nicte. "Characterization of the Electrical Resistivity and Water Sorption Properties of a Semiconducting Swelling Tape." Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-259662.
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I närvaro av fukt och lokaliserade fältförbättringar kan vattenträd utvecklas inom polymerisoleringen av HV subsea kraftkablar. Vattenträd tenderar att växa obemärligt och försämra isolationsegenskaperna med tiden. Fuktigheten i isoleringen kan effektivt reduceras genom applicering av halvledande svällningsband. Halvledande svullnadstejp ger en unik kombination av elektrisk ledningsförmåga och stor vattenhållande kapacitet. Detta hänför sig till förekomsten av ledande kolsvart (CB) respektive superabsorberande polymer (SAP) partiklar. För att förstå massatransportegenskaperna hos vattenånga inom ett svällande tejp bestämdes transportkoefficienterna. Sorptionen av vattenånga avslöjade koncentrationsberoende transportkoefficienter och en allmän ökning i diffusion och löslighet med ökande vattenaktivitet. Detta tillskrives SAP-komponenternas hygroskopiska och polyelektrolytegenskaper och resulterade i en ökning i diffusiviteten med en faktor 100, vid ökning av relativ fuktighet (RH) från 7 till 65%. Vid högre vattenaktivitet antogs att bildandet av immobila vattenklyftor minskade diffusionen av vattenånga. Flera sorptionslägen föreslogs för sorptionsbeteendet hos tejpen mellan 10 och 80% RH. Införandet av konduktivitet inom bandet minskar potentiella skillnader genom flera kabelskikt och efterföljande fältförbättringar. Konduktivitets- och vattensorptionsegenskaperna hos det halvledande svällningsbandet kan emellertid ändras genom mekaniska kompressioner, som utövas av omgivande kabelkomponenter. Den elektriska resistiviteten hos ett fuktigt svällande tejp under belastning bestämdes därför. På grund av bandets anisotropi utfördes elektriska resistivitetsmätningar över (radiell riktning) och tillsammans med (axiell riktning) tejpen. Bandens radiella och axiella riktningar dominerades av närvaron av SAP och CB. En signifikant minskning av bandets radiella resistivitet observerades när fuktigheten ökades från 40% till 60% RH. Resistiviteten minskade med en faktor 100. Ingen signifikant effekt av kompression observerades, men tejpen visade en minskande trend i resistivitet med ökande kompression. Vid 60% RH-radiell resistivitet närmade sig axiell resistivitet, och påverkan av SAP sänks. Den axiella resistiviteten var omkring 18 Ωcm. Tejpens axiella resistivitet påverkades mindre av fuktighet och kompression än den radiella resistiviteten. Åldrande avslöjar försämring av svullnadshöjd, men hade ingen inverkan på bandresistivitet.In presence of moisture and localized field enhancements water trees might develop within the polymeric insulation of HV subsea power cables. Water trees tend to grow unnoticeable and deteriorate the insulation properties with time. The humidity within the insulation can efficiently be reduced through the application of semiconducting swelling tapes. Semi conducting swelling tapes provide a unique combination of electrical conductivity and a large water retention capacity. This is attributed to the presence of conductive carbon black (CB) and superabsorbent polymer (SAP) particles, respectively. To understand the mass transport properties of water vapor within a swelling tape, transport coefficients were determined. The sorption of water vapor revealed concentration dependent transport coefficients and a general increase in diffusion and solubility with increasing water activity. This was attributed to the hygroscopic and polyelectrolyte properties of the SAP components and resulted in an increase in diffusivity by a factor of 100, when increasing the relative humidity (RH) from 7 to 65 %. At higher water activity, it was assumed that the formation of immobile water clusters reduced the diffusion of water vapor. Several sorption modes were suggested for the sorption behaviour of the tape between 10 to 80 % RH. The introduction of conductivity within the tape reduces potential differences throughout several cable layers and subsequent field enhancements. However, conductivity and water sorption properties of the semi-conductive swelling tape can be altered by mechanical compressions, exerted by surrounding cable components. The electrical resistivity of a humid swelling tape under load was therefore determined. Due to the anisotropy of the tape, electrical resistivity measurements were performed across (radial direction) and along with (axial direction) the tape. The radial and axial directions of the tape were dominated by the presence of SAPs and CBs, respectively. A significant reduction in radial resistivity of the tape was observed when increasing the humidity from 40 % to 60 % RH. The resistivity decreased by a factor of 100. No significant effect of compression was observed, but the tape showed a decreasing trend in resistivity with increasing compression. At 60 % RH radial resistivity approached axial resistivity, and the influence of SAPs is reduced. The axial resistivity was around 18 Ωcm. The axial resistivity of the tape was less affected by humidity and compression than the radial resistivity. Ageing reveal deterioration of swelling height, but had no influence on tape resistivity.
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Bonafè, Filippo. "Charge accumulation and transport in degenerately doped semiconducting polymers with mixed ionic and electronic conductivity." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/21710/.
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This thesis is part of the fields of Material Physics and Organic Electronics and aims to determine the charge carrier density and mobility in the hydrated conducting polymer–polyelectrolyte blend PEDOT:PSS. This kind of material combines electronic semiconductor functionality with selective ionic transport, biocompatibility and electrochemical stability in water. This advantageous material properties combination makes PEDOT:PSS a unique material to build organic electrochemical transistors (OECTs), which have relevant application as amplifying transducers for bioelectronic signals. In order to measure charge carrier density and mobility, an innovative 4-wire, contact independent characterization technique was introduced, the electrolyte-gated van der Pauw (EgVDP) method, which was combined with electrochemical impedance spectroscopy. The technique was applied to macroscopic thin film samples and micro-structured PEDOT:PSS thin film devices fabricated using photolithography. The EgVDP method revealed to be effective for the measurements of holes’ mobility in hydrated PEDOT:PSS thin films, which resulted to be <μ>=(0.67±0.02) cm^2/(V*s). By comparing this result with 2-point-probe measurements, we found that contact resistance effects led to a mobility overestimation in the latter. Ion accumulation at the drain contact creates a gate-dependent potential barrier and is discussed as a probable reason for the overestimation in 2-point-probe measurements.
The measured charge transport properties of PEDOT:PSS were analyzed in the framework of an extended drift-diffusion model. The extended model fits well also to the non-linear response
in the transport characterization and results suggest a Gaussian DOS for PEDOT:PSS. The PEDOT:PSS-electrolyte interface capacitance resulted to be voltage-independent, confirming the hypothesis of its morphological origin, related to the separation between the electronic (PEDOT) and ionic (PSS) phases in the blend.
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Neumann, Katharina [Verfasser], and Mukundan [Akademischer Betreuer] Thelakkat. "Triphenylamine based semiconducting polymers for organic/hybrid photovoltaics and sensors / Katharina Neumann ; Betreuer: Mukundan Thelakkat." Bayreuth : Universität Bayreuth, 2014. http://d-nb.info/1179705599/34.
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Bruchlos, Kirsten [Verfasser], and Sabine [Akademischer Betreuer] Ludwigs. "Influence of morphology on electrochemical redox processes in semiconducting polymers / Kirsten Bruchlos ; Betreuer: Sabine Ludwigs." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2019. http://d-nb.info/1195529392/34.
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Zhang, Mingfu. "Template controlled synthesis of magnetic, semiconducting nanoparticles within amphiphilic core shell cylindrical polymer brushes." [S.l.] : [s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=971864136.
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Shrestha, Roshan Prasad Irene Eugene A. "A study of optical and electronic properties of a semiconducting polymer, poly(o-methoxyaniline)." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2006. http://dc.lib.unc.edu/u?/etd,250.
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Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2006.Title from electronic title page (viewed Oct. 10, 2007). "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Chemistry." Discipline: Chemistry; Department/School: Chemistry.
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Erdmann, Tim. "High Charge Carrier Mobility Polymers for Organic Transistors." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-219832.
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I) Introduction
p-Conjugated polymers inherently combine electronic properties of inorganic semiconductor crystals and material characteristics of organic plastics due to their special molecular design. This unique combination has led to developing new unconventional optoelectronic technologies and, further, resulted in the evolution of semiconducting polymers (SCPs) as fundamental components for novel electronic devices, such as organic field-effect transistors (OFETs), organic light-emitting diodes (OLEDs) and organic solar cells (OSCs).[1–5] Moreover, the material flexibility, capability for thin-film formation, and solution processibility additionally allow utilizing modern printing technologies for the large-scale fabrication of flexible, light-weight organic electronics. This especially enables to significantly increase the production speed and, moreover, to drastically reduce the costs per unit.[6, 7] In particular, transistors are the most important elements in modern functional electronic devices because of acting as electronic switches in logic circuits or in displays to control pixels. However, due to molecular arrangement and interactions, the electronic performance of SCPs cannot compete with the one of monocrystalline silicon which is used in state-of-the-art high-performance microtechnology.[5, 8] Nonetheless, intensive and continuing efforts of scientists focused on improving the performance of OFETs, with the special focus on the charge carrier mobility, by optimizing the polymer structure, processing conditions and OFET device architecture. By this, it was possible to identify crucial relationships between polymer structure, optoelectronic properties, microstructure, and OFET performance.[8] Nowadays, the interdisciplinary scientific success is represented by high-performance SCPs with charge carrier mobilities exceeding the value of amorphous silicon.[3, 9] However, further research is essential to enable developing the next generation of electronic devices for application in healthcare, safety technology, transportation, and communication.
II) Objective and Results
Within the scope of this doctoral thesis, current high-performance p-conjugated SCPs should be studied comprehensively to improve the present understanding about the interdependency between molecular structure, material properties and charge transport. Therefore, the extensive research approaches focused on different key aspects of high charge carrier mobility polymers for organic transistors. The performed investigations comprised the impact of, first, novel design concepts, second, precise structural modifications and, third, synthetic and processing conditions and led to the major findings listed below.
1. The design concept of tuning the p-conjugation length allows to gradually modulate physical material properties and demonstrates that a strong localization of frontier molecular orbitals in combination with a high degree of thin-film ordering can provide a favorable platform for charge transport in p-conjugated semiconducting polymers.[1]
2. The replacement of thiophene units with thiazoles in naphthalene diimide-based p- conjugated polymers allows to increase interchain interactions and to lower frontier molecular orbitals. This compensates the potentially detrimental enhancement of backbone torsion and drives the charge transport to unipolar electron transport, whereas mobility values are partially comparable with those of the respective thiophene containing analogs.
3. p-Conjugated diketopyrrolo[3,4-c]pyrrole-based copolymers can be synthesized within fifteen minutes what, in combination with avoiding aqueous washings and optimizing processing conditions, allowed an increase in morphological and energetic order and, thus, improved the charge transport properties significantly.
III) Conclusion
The key findings of this doctoral thesis provide new significant insights into important aspects of designing, synthesizing and processing high charge carrier mobility polymers. By this, they can guide future research to further improve the performance of organic electronic devices - decisive for driving the development and fabrication of smart, functional and wearable next-generation electronics.
References
[1] T. Erdmann, S. Fabiano, B. Milián-Medina, D. Hanifi, Z. Chen, M. Berggren, J. Gierschner, A. Salleo, A. Kiriy, B. Voit, A. Facchetti, Advanced Materials 2016, 28 (41), 9169–9174, DOI:10.1002/adma.201602923.
[2] Y. Karpov, T. Erdmann, I. Raguzin, M. Al-Hussein, M. Binner, U. Lappan, M. Stamm, K. L. Gerasimov, T. Beryozkina, V. Bakulev, D. V. Anokhin, D. A. Ivanov, F. Günther, S. Gemming, G. Seifert, B. Voit, R. Di Pietro, A. Kiriy, Advanced Materials 2016, 28 (28), 6003–6010, DOI:10.1002/adma.201506295.
[3] A. Facchetti, Chemistry of Materials 2011, 23 (3), 733–758, DOI:10.1021/cm102419z.
[4] A. J. Heeger, Chemical Society Reviews 2010, 39, 2354–2371, DOI:10.1039/B914956M.
[5] H. Klauk, Chemical Society Reviews 2010, 39, 2643–2666, DOI:10.1039/B909902F.
[6] S. G. Bucella, A. Luzio, E. Gann, L. Thomsen, C. R. McNeill, G. Pace, A. Perinot, Z. Chen, A. Facchetti, M. Caironi, Nature Communications 2015, 6, 8394, DOI:10.1038/ncomms9394.
[7] H. Sirringhaus, T. Kawase, R. H. Friend, T. Shimoda, M. Inbasekaran, W. Wu, E. P. Woo, Science 2000, 290 (5499), 2123–2126, DOI:10.1126/science.290.5499.2123.
[8] D. Venkateshvaran, M. Nikolka, A. Sadhanala, V. Lemaur, M. Zelazny, M. Kepa, M. Hurhangee, A. J. Kronemeijer, V. Pecunia, I. Nasrallah, I. Romanov, K. Broch, I. McCulloch, D. Emin, Y. Olivier, J. Cornil, D. Beljonne, H. Sirringhaus, Nature 2014, 515 (7527), 384–388, DOI:10.1038/nature13854.
[9] S. Holliday, J. E. Donaghey, I. McCulloch, Chemistry of Materials 2014, 26 (1), 647–663, DOI: 10.1021/cm402421p.
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Müller, Lars [Verfasser], and Wolfgang [Akademischer Betreuer] Kowalsky. "On the Correlation Between Structural Order and Molecular Doping in Semiconducting Polymers / Lars Müller ; Betreuer: Wolfgang Kowalsky." Heidelberg : Universitätsbibliothek Heidelberg, 2018. http://d-nb.info/1177384000/34.
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Urrego, Riveros Sara [Verfasser]. "Synthesis of New Monomers for Semiconducting Polymers and Their Application in Organic Optoelectronic Devices / Sara Urrego Riveros." Kiel : Universitätsbibliothek Kiel, 2019. http://d-nb.info/1196090955/34.
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Al, Haik Mohammad Yousef. "Nanoparticle-based Organic Energy Storage with Harvesting Systems." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/79815.
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A new form of organic energy storage devices (organic capacitors) is presented in the first part of this dissertation. The storage devices are made out of an organic semiconductor material and charge storage elements from synthesized nanoparticles. The semiconducting polymer is obtained by blending poly (vinyl alcohol) and poly (acrylic acid) in crystal state polymers with a known plasticizer; glycerol or sorbitol. Synthesized nanoparticles namely, zinc-oxide (ZnO), erbium (Er), cadmium sulfide (CdS), palladium (Pd) and silver-platinum (AgPt) were used as charge storage elements in fabrication of metal-insulator-semiconductor (MIS) structure. The organic semiconductor and synthesized nanoparticles are tested to evaluate and characterize their electrical performance and properties. Fabrication of the organic capacitors consisted of layer-by-layer deposition and thermal evaporation of the electrode terminals. Capacitance versus voltage (C-V) measurement tests were carried out to observe hysteresis loops with a window gate that would indicate the charging, discharging and storage characteristics. Experimental investigation of various integrated energy harvesting techniques combined with these organic based novel energy storage devices are performed in the second part of this dissertation. The source of the energy is the wind and is harvested by means of miniature wind turbines and vibrations, using piezoelectric transduction. In both cases, the generated electric charge is stored in these capacitors. The performance of the organic capacitors are evaluated through their comparison with commercial capacitors. The results show that the voltage produced from the two energy harvesters was high enough to store the harvested energy in the organic capacitors. The charge and energy levels of the organic capacitors are also reported.
The third part of this dissertation focuses on harvesting energy from a self-induced flutter of a thin composite beam. The composite beam consisted of an MFC patch bonded near the clamped end and placed vertically in the center of a wind tunnel test section. The self sustaining energy harvesting from the unimorph composite beam is exploited. The effects of different operational parameters including the optimum angle of attack, wind speed and load resistance are determined.Ph. D.
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Richardson, Scott. "The fabrication and lithography of conjugated polymer distributed feedback lasers and development of their applications." Thesis, St Andrews, 2007. http://hdl.handle.net/10023/401.
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Curley, John F. "The synthesis and characterisation of novel semiconduction ladder polymers and their use as conductive fillers in composite materials." Thesis, Kingston University, 1997. http://eprints.kingston.ac.uk/20357/.
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A series of ladder polymers have been synthesised from polycondensation reactions between phenazinium based monomers such as safranine O and acridine yellow G and benzoquinone type monomers. The same polymeric products were obtained regardless of whether the polymerisations were carried out in polyphosphoric acid, in organic solvent, or in the absence of solvent in the solid phase. However, the degree of completed ladder structure contained within the polymer was found to vary with different synthesis techniques. In general the ladder polymer prepared in PPA was superior in terms of intrinsic viscosity (molecular weight) and thermal stability in comparison to the same polymer prepared in organic solvent or in the solid phase. The polymer solubilities were poor in organic solvents and attempts to increase their solubilities with the introduction of bulky side-groups into the polymer structure was successful only in producing soluble single-strand polymers. The electrical conductivities (o) of the polymers lay in semi-conducting range with a clear trend showing that: 0PPA > 0DMAc/S.P. > 0single-strand > 0two-stagepolymers. The electrical conductivity was found to be stable for at least 30 days at incubation temperatures as high as 250° C. Temperature dependent conductivity studies show that plots of o versus T1/4 are not perfectly linear, although correlation coefficients for plots against '11/4 and T1[beta] show that the data tends to favour Mott's three-dimensional conduction model. Composite samples of thermoplastic PMMA and thermosetting polyester with ladder polymer showed percolation thresholds at 7.9% v/vand 8.6% viv filler loadings respectively with maximum conductivities close to those of the pristine polymer at filler loadings of 11.2% v/vand 13.0% vl» respectively. The temperature dependence of PMMA/ladder composites showed PTC behaviour between the softening point and melting point of PMMA with NTC behaviour thereafter. Thermosetting polyester composites showed little temperature sensitivity up to the point of thermal degradation at which catastrophic, permanent loss in conductivity occurred. The electrical conductivity of ladder/PMMA samples was found to be stable for at least 30 days at 250°C.
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Sprick, Reiner Sebastian. "Polytriarylamines containing fused ring and heterocyclic structures prepared using N-heterocyclic carbene complexes of palladium." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/polytriarylamines-containing-fused-ring-and-heterocyclic-structures-prepared-using-nheterocyclic-carbene-complexes-of-palladium(c09188eb-490b-452c-945a-22979f58c76d).html.
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For the preparation of semiconducting polymers often ‘standard’ catalytic systems are used without further optimisation. New ligands, such as N-heterocyclic carbenes have shown excellent activity in cross-coupling reactions (e.g. Suzuki-Miyaura reaction, or Hartwig-Buchwald amination). These systems show excellent conversions under mild conditions and even allow the use of aryl chlorides as reagents. Nevertheless, previously no system has been reported for the synthesis of conjugated polymers, e.g. the Suzuki polycondensation or Buchwald-Hartwig type polycondensation using these catalysts. A NHC-Pd based catalytic system was optimised for a polyamination reaction and the catalyst [(IPr)Pd(allyl)Cl] was found to be the most active. Polytriarylamines were synthesised using the optimised catalytic system and tested in organic field-effect transistors. Mobilities found were low which was found to be attributed to the presence of high molecular weight fractions. Molecular weights were controlled using an in situ end-capping approach and polymers tested in the semiconducting layer of OFETs gave similar mobilities tothose reported earlier. Several polytriarylamines, which have not been reported previously, were synthesised using NHC-chemistry and the in situ end-cappingapproach, as well as polytriarylamines that have been reported previously using Pd/phosphine catalysts. One library containing polymers based on biphenyles andbridged biphenyles and another library containing polymers with bridged oligoarenes were synthesised. Suzuki polycondensation was also studied besides the polyamination protocol and low catalyst loadings and reaction temperatures could be realised using a NHC-Pd catalyst. Sulfur containing monomers that could not be polymerised using the polyamination were polymerised successfully. All polymers were fully characterised and studied as the active layer in organic field-effect transistors. The highest mobilities determined for these polymers (~10-2 cm2/Vs) is close to the highest reported for this class of polymer reported to date.
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James, Robinson. "Novel Carborane Derived Semiconducting Thin Films for Neutron Detection and Device Applications." Thesis, University of North Texas, 2015. https://digital.library.unt.edu/ark:/67531/metadc804945/.
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Novel carborane (B10C2H12) and aromatic compounds (benzene, pyridine, diaminobenzene) copolymers and composite materials have been fabricated by electron beam induced cross-linking and plasma enhanced chemical vapor deposition (PECVD) respectively. Chemical and electronic structure of these materials were studied using X-ray and ultra-violet photoelectron spectroscopy (XPS and UPS). UPS suggest that the systematic tuning of electronic structure can be achieved by using different aromatic compounds as co-precursors during the deposition. Furthermore, top of valence band is composed of states from the aromatic moieties implying that states near bottom of the conduction band is derived from carborane moieties. Current- voltage (I-V) measurements on the ebeam derived B10C2HX: Diaminobenzene films suggest that these films exhibit enhanced electron hole separation life time. Enhanced electron hole separation and charge transport are critical parameters in designing better neutron voltaic devices. Recently, PECVD composite films of ortho-carborane and pyridine exhibited enhanced neutron detection efficiency even under zero bias compared to the pure ortho-carborane derived films. This enhancement is most likely due to longer electron-hole separation, better charge transport or a combination of both. The studies determining the main factors for the observed enhanced neutron detection are in progress by fabricating composite films of carborane with other aromatic precursors and by altering the plasma deposition conditions. This research will facilitate the development of highly sensitive and cost effective neutron detectors, and has potential applications in spintronics and photo-catalysis.
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Melo, Washington Luiz de Barros. "Contribuições as técnicas de espectroscopias fototérmicas e aplicações a materiais poliméricos." Universidade de São Paulo, 1992. http://www.teses.usp.br/teses/disponiveis/54/54132/tde-15042014-105521/.
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A espectroscopia foto-térmica tem sido largamente usada na investigação de propriedades térmicas e ópticas de materiais sólidos. Neste trabalho, desenvolvemos novas câmaras foto-térmicas as quais foram adaptadas para os estudos de materiais poliméricos. Estendemos o modelo desenvolvido por Mandelis para a espectroscopia fotopiroelétrica (PPES), incluindo nele um termo devido à reflexão de luz na interface amostra-detetor. A aplicação da técnica PPES em filmes de Poli(3-Butiltiofeno) não dopado nos permitiu obter sua condutividade e difusividade térmicas, como também seu gap de energia. Também aplicamos a técnica fotoacústica, com um flash de laser He-Ne, ao estudo de filmes de polímeros transparentes. Finalmente, desenvolvemos um método semi-empírico o qual significa a análise do sinal foto-térmico, quando ele é, principalmente, devido à difusão térmica.Photothermal spectroscopies have been largely used in the investigation of thermal and optical properties of solids materials. In this work we developed new photothermal cells which were adapted for the study of polymerics materials. We also extended the model developed by Mandelis for the Photopyroeletric Spectroscopy (PPES), including in it a term due to the reflected light in the sample-detector interface. The application of the PPES technique in films of undopedpoly(3-butylthiophene) allowed us to obtain its thermal conductivity and diffusivity, as well as its gap energy. We also applied the photoacoustic technique, with a flash of He-Ne laser to study of transparent films of polymers. Finally we developed a semi-empiric method which simplifies the analysis of the photothermal signal, when it is mainly due to the thermal diffusion.