Understanding the Structure-Function Relationship of Semiconducting Polymers Through Chemical and Electrochemical Doping
Understanding the Structure-Function Relationship of Semiconducting Polymers Through Chemical and Electrochemical Doping

Author: Charlene Zarah Salamat

Publisher:

Published: 2023

Total Pages: 0

ISBN-13:

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Conjugated polymers are a versatile class of materials useable in a variety of organic electronic applications, but their utilization is limited by their intrinsically low conductivity. However, doping of semiconducting polymers via oxidation of their backbone can add mobile charge carriers and increase their electrical conductivity. This can be accomplished via electrochemical doping, where an applied potential oxidizes the polymer, or via chemical doping, where a molecular oxidizer is introduced to the polymer.Electrochemical doping of semiconducting polymers is of interest because of this class of material's ability to be utilized in electrochemical cells, such as lithium-ion batteries (LIBs). This is explored in the first part of this dissertation (Chapters 2 through 7), where we investigate the application of semiconducting polymers as LIB binders. Binders are typically designed to be chemically and mechanically durable during cycling. Utilizing conjugated polymers as binders increases the electrical conductivity of the electrode, leading to reduced resistive losses and faster charging. We show that dihexyl-substituted poly(3-4-propylenedioxy-thiophene) (PPrODOT-Hx2) can serve as a binder at relevant electrochemical potentials. Additionally, we show that by either creating co-polymers with oligoether side-chains or by adding conjugation break-spacer units, we can tune ionic conductivity, heat generation, swelling, and the mechanical properties of the semiconducting polymers. While electrochemical doping has the advantage of allowing the selection of an exact potential (i.e., doping level), chemical doping is advantageous because it is fairly simple to accomplish. In the second half of this dissertation (Chapters 8 through 12), we study a variety of semiconducting polymers and dopants to understand what results in the highest conductivity in chemically doped semiconducting films. We explore the energetics and the role of crystallinity, dielectric constant, and Coulomb binding in chemical doping. Throughout this dissertation, we utilize grazing incidence wide-angle X-ray scattering (GIWAXS) to see how the structure of these polymers change upon doping, and how these structural changes map onto changes in both electronic and ionic conductivity, and optical properties.

Understanding Structure-Function Relationships in Semiconducting Polymer Morphology
Understanding Structure-Function Relationships in Semiconducting Polymer Morphology

Author: Katharine Adele Winchell

Publisher:

Published: 2020

Total Pages: 336

ISBN-13:

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Semiconducting polymers are a promising class of materials for many organic electronic applications because of their structural tunability, low cost, and solution processability, which allows for easy scale-up. However, semiconducting polymers have intrinsically poor conductivity which limits their performance in all device applications. Polymer conductivity can be improved either by adding mobile carriers to the system or by manipulating the system to make the polymer chains more ordered on a local and global scale. This thesis studies both of these methods with a goal of improving polymer conductivity, while simultaneously seeking to understand how changes in morphology affect both local and global polymer properties. We used a variety of X-ray and neutron scattering techniques to characterize polymer structure, coupled with electronic and spectroscopic experiments to gain a full picture of polymer structure-function relationship. The first half of this thesis studies the structural changes that result from introducing a molecular dopant and additional charge carriers into the polymer network, and how those change control the resulting electronic and optical properties. We start by studying a novel class of large, redox-tunable dodecaborane-based dopants. From these studies we are able to determine how redox potential controls both dopant infiltration into polymer films and the resulting film structure, providing insight into the relationship between structure and conductivity for doped conjugated polymer systems. Using traditional small-molecule dopants, we also studied various doping methods to assess scalability and application to thick polymer films. The second half of this thesis presents studies on various methods to manipulate the local morphology of polymer chains to increase their overall order. We first used an aqueous amphiphilic self-assembly system where we developed structural design rules for order assembly and demonstrate that they can be used to create polymer system that show straightened chains when self-assembled. Next, we explored a set of block-copolymers whose co-crystallization properties could be changed using the polymer molecular weight; here we show that crystallization behavior directly affects conductivity. Lastly, we studied a host-guest system of polymers aligned in straight silica mesoporous, with a goal of using confinement to understand the interplay between polymer microstructure and aggregation.

Semiconducting Polymers
Semiconducting Polymers

Author: Georges Hadziioannou

Publisher: John Wiley & Sons

Published: 2006-12-15

Total Pages: 786

ISBN-13: 3527312714

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The field of semiconducting polymers has attracted many researchers from a diversity of disciplines. Printed circuitry, flexible electronics and displays are already migrating from laboratory successes to commercial applications, but even now fundamental knowledge is deficient concerning some of the basic phenomena that so markedly influence a device's usefulness and competitiveness. This two-volume handbook describes the various approaches to doped and undoped semiconducting polymers taken with the aim to provide vital understanding of how to control the properties of these fascinating organic materials. Prominent researchers from the fields of synthetic chemistry, physical chemistry, engineering, computational chemistry, theoretical physics, and applied physics cover all aspects from compounds to devices. Since the first edition was published in 2000, significant findings and successes have been achieved in the field, and especially handheld electronic gadgets have become billion-dollar markets that promise a fertile application ground for flexible, lighter and disposable alternatives to classic silicon circuitry. The second edition brings readers up-to-date on cutting edge research in this field.

Semiconducting Polymers
Semiconducting Polymers

Author: Raquel Aparecida Domingues

Publisher: CRC Press

Published: 2021-06-25

Total Pages: 220

ISBN-13: 1000727726

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Semiconducting polymers are of great interest for applications in electroluminescent devices, solar cells, batteries, and diodes. This volume provides a thorough introduction to the basic concepts of the photophysics of semiconducting polymers as well as a description of the principal polymerization methods for luminescent polymers. Divided into two main sections, the book first introduces the advances made in polymer synthesis and then goes on to focus on the photophysics aspects, also exploring how new advances in the area of controlled syntheses of semiconducting polymers are applied. An understanding of the photophysics process in this kind of material requires some knowledge of many different terms in this field, so a chapter on the basic concepts is included. The process that occurs in semiconducting polymers spans time scales that are unimaginably fast, sometimes less than a picosecond. To appreciate this extraordinary scale, it is necessary to learn a range of vocabularies and concepts that stretch from the basic concepts of photophysics to modern applications, such as electroluminescent devices, solar cells, batteries, and diodes. This book provides a starting point for a broadly based understanding of photophysics concepts applied in understanding semiconducting polymers, incorporating critical ideas from across the scientific spectrum.

Structure-Function Relationships in Semiconducting Polymers for Organic Photovoltaics
Structure-Function Relationships in Semiconducting Polymers for Organic Photovoltaics

Author: David Fredric Joel Kavulak

Publisher:

Published: 2010

Total Pages: 242

ISBN-13:

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The major body of this work investigates how the chemical structure of conjugated polymers relates to the fundamental operating mechanism of organic photovoltaic devices. New conjugated polymers were characterized and their optical and electronic properties tested and correlated with their power conversion efficiencies as the active layer in polymer solar cells. From these experiments general structure/function relationships are drawn with an eye toward developing universal guidelines for conjugated polymer design and synthesis. Starting with light absorption, three major steps in the photovoltaic mechanism are examined. First, photogeneration of excited states and the migration of these states through the active layer are correlated to the polymeric backbone chemistry and the resulting device performance. Next, separation of these excited states at an interface between electron donors and electron acceptors is examined as a function of donor-acceptor distance and active layer dielectric constant. These two variables were tuned by chemical modification of polythiophene side groups. Third, charge carrier conduction is related to both polymer electronic states and to solid-state packing morphology. Design principles for effective conduction of both holes and electrons are outlined and the ambipolar nature of conjugated organic materials is discussed. In the final chapters, the solid-state polymer morphology in a solution processed thin film is examined. The impact that this morphology has on all steps in the photovoltaic mechanism is highlighted. How chemical modification of the polymer can influence this packing structure is examined as well as how new fabrication procedures can be used to pre-form nanostructured materials in solution before thin film deposition.

Structure and Electronic Property Relationships in Chemically Doped Semiconducting Polymers and Polymer Photovoltaics
Structure and Electronic Property Relationships in Chemically Doped Semiconducting Polymers and Polymer Photovoltaics

Author: Taylor Aubry-Komin

Publisher:

Published: 2019

Total Pages: 201

ISBN-13:

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This work is focused on understanding how molecular-level structural control can improve charge carrier properties in -conjugated polymers. Conjugated polymers are characterized by extended conjugation along their backbone, making them intrinsically semiconducting materials that are of interest for a wide variety of flexible, thin-film electronic applications. Polymeric semiconductors possess advantages over inorganic materials such as being lightweight, low-cost and solution processable. However, due the disordered nature of conjugated polymers and their anisotropic transport, charge carrier dynamics can be highly sensitive to structural effects. The first chapter of this dissertation gives an introduction to conjugated polymers and their relevant applications as well as how tuning morphology and doping level can influence their charge carrier properties. The second introduces a technique, known as sequential processing (SqP), that affords control over polymer domain orientation when preparing polymer films as the active layer in optoelectronic devices. We show that conventional processing methods lead to disordered, isotropic polymer networks. By contrast, SqP can be used to preserve the preferred face-on chain orientation seen with some polymer materials, yielding advantages for photovoltaics and other devices via increased vertical hole mobility. Chapter 3 turns to molecular doping of conjugated polymers and studies the effects of a bulky boron cluster dopant used to modify the charge transport properties of conjugated polymers. The design of the dopant is such that it sterically protects core-localized electron density, resulting in shielding of the electron from holes produced on the polymer. This allows the charge carriers to be highly delocalized, as confirmed both spectroscopically and by AC-Hall effect measurements. The dopants allow for high carrier mobilities to be achieved even for non-crystalline polymers. The implication is that the counterion distance is the most important factor needed to produce high carrier mobility in conjugated polymers. In the last chapter, we study a series of boron cluster dopants in which the redox potential is tuned over a large range but the anion distance is fixed. In the last chapter, we study a series of boron cluster dopants in which the redox potential is tuned over a large range but the anion distance is fixed. This allows us to disentangle the effects of energetic offset in doping on the production of free carriers. We find that the redox potential not only affects the generation of free carriers, but also the infiltration of dopants into the polymer films.

Doping in Conjugated Polymers
Doping in Conjugated Polymers

Author: Pradip Kar

Publisher: John Wiley & Sons

Published: 2013-08-01

Total Pages: 176

ISBN-13: 1118816617

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An A-to-Z of doping including its definition, its importance, methods of measurement, advantages and disadvantages, properties and characteristics—and role in conjugated polymers The versatility of polymer materials is expanding because of the introduction of electro-active behavior into the characteristics of some of them. The most exciting development in this area is related to the discovery of intrinsically conductive polymers or conjugated polymers, which include such examples as polyacetylene, polyaniline, polypyrrole, and polythiophene as well as their derivatives. "Synmet" or "synthetic metal" conjugated polymers, with their metallic characteristics, including conductivity, are of special interest to researchers. An area of limitless potential and application, conjugated polymers have sparked enormous interest, beginning in 2000 when the Nobel Prize for the discovery and development of electrically conducting conjugated polymers was awarded to three scientists: Alan J. Heeger, Alan G. MacDiarmid, and Hideki Shirakawa. Conjugated polymers have a combination of properties—both metallic (conductivity) and polymeric; doping gives the conjugated polymer's semiconducting a wide range of conductivity, from insulating to low conducting. The doping process is a tested effective method for producing conducting polymers as semiconducting material, providing a substitute for inorganic semiconductors. Doping in Conjugated Polymers is the first book dedicated to the subject and offers a comprehensive A-to-Z overview. It details doping interaction, dopant types, doping techniques, and the influence of the dopant on applications. It explains how the performance of doped conjugated polymers is greatly influenced by the nature of the dopants and their level of distribution within the polymer, and shows how the electrochemical, mechanical, and optical properties of the doped conjugated polymers can be tailored by controlling the size and mobility of the dopants counter ions. The book also examines doping at the nanoscale, in particular, with carbon nanotubes. Readership The book will interest a broad range of researchers including chemists, electrochemists, biochemists, experimental and theoretical physicists, electronic and electrical engineers, polymer and materials scientists. It can also be used in both graduate and upper-level undergraduate courses on conjugated polymers and polymer technology.

Studying and Controlling the Structure of Doped Semiconducting Polymers
Studying and Controlling the Structure of Doped Semiconducting Polymers

Author: Yutong Wu

Publisher:

Published: 2022

Total Pages: 0

ISBN-13:

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This thesis focuses on studying and controlling the structure of pristine and doped semiconducting polymers. Semiconducting polymers have many applications in flexible electronics due to their structural tunability, low cost and solution processability. Intrinsically, semiconducting polymers have poor conductivities due to a lack of mobile carriers. Charge transfer between a semiconducting polymer and a dopant molecule is necessary to introduce carriers into a polymer system. If an electron is fully transferred, commonly called "integer charge transfer (ICT)", this will result in a polaron and a dopant anion. On the other hand, the electron charge could be shared between the polymer and a dopant molecule to form a "charge transfer complex (CTC)". In the first part of the thesis, we explored factors that affect the charge transfer pathways in doped semiconducting polymers and were able to control the formation of CTCs. Semiconducting polymers are composed of both crystalline and amorphous parts. Compared to crystalline regions, amorphous polymer parts are disordered, thus the dopant anion is usually close to the polarons, resulting in poor carrier mobility due to Columb attraction between polarons and counterions. CTCs also tend to form in amorphous polymer regions compared to crystallites and result in less carriers due to the charge-sharing nature of CTC. In our second project, we explored ways to suppress the formation of both CTCs and localized carriers even in highly amorphous polymer films, using large boron cluster-based dopants. The electron density of these dopants is core-localized and is shielded from the holes on the polymer, resulting in increased crystallinity and higher film conductivities. In our third project, we further explored how polymer crystallite orientation influences the ease of doping and found that polymer regions with structures similar to the final doped structure could be doped more easily. In the last chapter, we designed amphiphilic semiconducting polyelectrolytes that form ordered cylindrical micelles in water. Our results demonstrate that we can achieve relatively precise control between electron donor and acceptor co-assemblies by varying the structural properties of component amphiphilic polymers and acceptors, which can provide guidelines for designing systems with controllable excited-state transfers.