Effect of Incorporating Iridium in Conjugated Polymers on Light-emitting and Photovoltaic Properties PDF Download

Author: Gisela Louisa Schulz
Publisher:
ISBN:
Category : Conjugated polymers
Languages : en
Pages : 0

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Chemical and structural characteristics of conjugated polymers give rise to their light-emitting and photovoltaic properties. This thesis reports on the synthesis and characterization of iridium-bound conjugated polymers. Suzuki polycondensation was used to make host-guest, alternating copolymers with iridium content varying from 0 to 40 mol %. Structure-property relationships were investigated using a wide variety of techniques including NMR, UV-vis absorption, X-ray fluorescence, and photoluminescent spectroscopies, cyclic voltammetry, gel permeation chromatography, light emitting devices and photovoltaic devices. Energy transfer in the host-guest systems from the polymer backbone to the iridium complex was studied in dilute solutions and thin films, and investigated with respect to iridium content. The relative rates of photophysical processes were used to explain the observed emission properties and correlated to polymer structure. Exchanging the 2,5-linked pyridine group with a 3,4-linked thiophene in the polymer backbone of polyfluorene copolymers, increased the polymer triplet energy level, which resulted in decreasing the back energy transfer from the iridium triplet state to the polymer triplet state. The work presented in Chapter 2 demonstrates the importance of the relative position of the triplet energy level of the polymer in comparison to the position of the triplet level of the iridium complex. The effect of triplet excitons on charge generation in photovoltaic devices was investigated. Incorporation of iridium into a polyfluorene backbone resulted in a 10-fold increase in the ratio of incident photons to converted electrons (also known as external quantum efficiency). However, when iridium was incorporated into a poly(fluorene-alt-bithiophene) polymer, photovoltaic performance decreased, thus revealing the complexity of the requirements necessary for efficient photon to electron conversion. In the case of poly(fluorene-co-bithiophene-co-iridium) it is believed that the morphology of the polymer:[6,6]-phenyl C61 butyric acid methyl ester blend plays a dominate role in determining photovoltaic properties. The structure-property relationships identified in this work build on the current understanding of iridium-bound conjugated polymers, and may be relevant to other conjugated polymer systems. The relationships drawn from this work should prove useful for the design of new polymers for light-emitting and photovoltaic applications.

Author: Brian Frank Morgan
Publisher:
ISBN:
Category : Conjugated polymers
Languages : en
Pages : 194

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This dissertation explores the effects which illumination has on the structure and conformation of conjugated polymers, both in solution and the bulk. Conjugated polymers are an important class of optoelectronic polymeric materials which make up the active layer of key organic electronic devices such as organic photovoltaics, transistors, and light emitting diodes. Considering the strong link between polymer chain structure and device efficiency in these materials, a comprehensive understanding of certain experimental conditions which may influence this conformation and thusly alter the functionality of the devices predicated upon them is of vital importance. The first part of this dissertation provides a background to conjugated polymers, their role in common electronic applications, and the known effects of illumination on polymeric materials. The next section outlines an initial exploration of light induced effects on benchmark conjugated polymers in solution elucidated via the use of small angle neutron scattering. The third chapter explores the structural evolution of solution gels formed from conjugated polymers at multiple length scales using small and ultra small angle scattering, as well as quantifying modifications to this structural progression brought on by white light exposure. The fourth and fifth chapters further expand our understanding of the proposed thermodynamic driving forces behind the light induced structural changes in conjugated polymer solutions first through alterations in solvent quality, and then through fine-tuning of incident light wavelength, exposure time, and intensity. Finally, the sixth section studies the self-assembly of conjugated polymer composite thin films cast from a single solution through neutron reflectivity, while additionally monitoring the effects of light exposure during the thermal annealing process upon the final film depth profile. Ultimately, these works cumulatively provide strong evidence indicating that light exposure is in fact an important parameter with far-reaching implications upon the final structure of organic electronic materials. Overlooking illumination conditions and failing to provide a consistent ambient light environment throughout device fabrication will result in non-uniform chain conformations and layering architectures, inevitably impacting device performance. However, if properly understood and harnessed, these light-induced effects could make possible an entirely novel methodology for in-situ tuning of organic electronic device physical parameters.

Author: Haichang Zhang
Publisher: Frontiers Media SA
ISBN: 2889664813
Category : Science
Languages : en
Pages : 126

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Author: Hao Chang
Publisher:
ISBN:
Category :
Languages : en
Pages : 82

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Organic photovoltaic cells (OPV’s), renewable energy devices that can convert sunlight into electricity, have a bright future. However, the low power conversion efficiency (PCE) of OPV’s is a challenge in their development. To improve the PCE of an OPV, many factors need to be considered, such as light absorption, the fundamental gap, the optical gap, and the OPV’s film thickness. The addition of heteroatoms to conjugated polymers is a way to change the electronic properties of the donors and may improve the PCE. This thesis describes the use of computational methods to determine how oxygen and sulfur atoms affect the electronic properties of a conjugated polymer. The data suggest that the fundamental gaps and binding energies decrease after replacing oxygen with sulfur. Additionally, incorporating a sulfur atom into the conjugated polymer can increase the dipole moment change, which may lead to accelerated charge dissociation and may reduce charge recombination.

Author: Samodha Subhashini Gunathilake
Publisher:
ISBN:
Category : Aldol condensation
Languages : en
Pages : 302

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Book Description
Conjugated polymers are promising materials that can be used in organic electronic devices, such as organic field effect transistors, organic solar cells, and organic light emitting diodes. They have some advantages over their inorganic counterparts such as solution proccesability, light weight, and easy device fabrication. These properties largely reduce the manufacturing cost of these devices. Different functional moieties can be incorporated in conjugated polymers to tune the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels, thus to control the band gap and to enhance their opto-electronic properties. These properties include good solubility, improved packing in solid state, and enhanced solar energy absorption. Pyrimidine has been incorporated in conjugated polymers due to its important properties such as electron withdrawing nature, pH sensitivity, and ability to participate in hydrogen bonding and coordinate various metal ions. Due to the electron deficient nature, pyrimidine polymers have low lying LUMO levels and have been applied in organic electronic devices as n-type semiconductors. Out of many functional moieties, thiophene ring is one of the most used units in conjugated polymers, because poly(thiophene)s possess good electronic properties. By incorporating alkoxy substituents on poly(thiophene)s the HOMO energy level of the polymers can be increased, resulting in low band gap polymers. These polymers are promising materials to be used in organic electronic devices. Chapter 1 discusses conjugated polymers used in organic electronic devices, their charge transport mechanisms, doping to improve the conductivity, and working mechanisms of organic electronic devices such as organic field effect transistors and solar cells. It also describes the potential use of these materials as a precursor for graphene. It further discusses pyrimidine conjugated polymers and poly(alkoxythiophene)s. Chapter 2 discusses the aldol condensation reactions to incorporate pyrimidine in conjugated polymers. It describes the synthesis, characterizations and optoelectronic properties of pyrimidine containing conjugated polymers. Chapter 3 discusses the synthesis of nitrogen containing graphitic materials by using pyrimidine conjugated polymers as the precursor. It describes the synthesis and characterizations of precursor polymers, nitrogen doped graphitic materials, and the application of these materials in polymer/graphene hybrid field effect transistors. Chapter 4 discusses the synthesis of poly(alkoxythiophene)s by McCullough method. It describes the synthesis, characterization of these polymers and oxidative doping to increase conductivity.

Author: Tanmoy Dey
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages :

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Electrochromism is a process by which a material can change its electronic-optical properties upon charge injection/removal. Conjugated polymers are an interesting class of electrochromic materials because of their color tunability, high optical contrasts, fast switching speeds, and processability. Poly(3,4-propylenedioxy)thiophenes (PProDOT) are a substantial subclass of materials in conjugated polymer electrochromics due to their high optical contract between the bleached and colored states. Common derivatives of this molecule are typically made at the beta position with respect to oxygen on the seven membered ring. PProDOTs with methyl and benzyl substituents (beta position with respect to oxygen) are two of the more successful due to their high contrast. We have found that there is a much more substantial effect when PProDOT is derivatized in the positions alpha to the oxygen. For example, two t-butyl groups with each placed alpha to the oxygen in PProDOT incurs a 200 nm shift in the lambda max (365 nm) compared to having two methyl groups with each placed alpha to the oxygen. The dimethyl derivative is blue in color whereas the di-t-butyl, dihexyl, diisopropyl is showing yellow, orange and red color respectively. The polymer of this new derivative, P13ProDOT-TB2 and P13ProDOT-Hex 2 is organic-soluble and can be processed by a variety of solution methods, including spray coating. Furthermore we have also studied some selenium based polymer for electrochromic application. Poly(3,4-propylenedioxy)selenophenes (PProDOS) is showing better optical contrast, stability and faster switching speed as compared to their sulfur analogs. Low band gap conducting polymers (CPs) have relatively low absorption in the visible region, in their conducting states, making them promising candidates for optically transparent electrode, hole-injection layer for light-emitting diodes and suitable donor material for Photovoltaics. The monomer, Seleno[3,2- c]thiophene and Seleno[3,4-b]thiophene, were electrochemically and polymerized to produce new low band gap conducting polymer, poly(Seleno[3,2- c]thiophene) (PS32cT) and Poly(Seleno[3,4-b]thiophene) (PS34bT), having a low band gap of 1.03 eV and 1.50 eV respectively. Besides from the suitable energy gap, they also offer a good match of the absolute energy levels with the other materials in the photovoltaic device. The HOMO of the low band gap polymers agree with the work function of ITO and LUMO matches with the acceptor level of PCBM. This overlap is very important to the function of photovoltaic devices. In a different approach we describe a new alternative route for the synthesis of thieno[3,4-b]thiophene, alkyl derivatives thereof, seleno[3,4- b]thiophene, and thieno[3,4-b]furan made from inexpensive starting materials, such as thiophene-2-carboxylic acid and furan-2-carboxylic acid. Such fused heterocycles are of great interest for low band gap organic semiconductors and applications including OLEDs, organic photovoltaic cells, and electrochromic applications.

Author: Beata Luszczynska
Publisher: John Wiley & Sons
ISBN: 352734442X
Category : Technology & Engineering
Languages : en
Pages : 686

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Book Description
Provides first-hand insights into advanced fabrication techniques for solution processable organic electronics materials and devices The field of printable organic electronics has emerged as a technology which plays a major role in materials science research and development. Printable organic electronics soon compete with, and for specific applications can even outpace, conventional semiconductor devices in terms of performance, cost, and versatility. Printing techniques allow for large-scale fabrication of organic electronic components and functional devices for use as wearable electronics, health-care sensors, Internet of Things, monitoring of environment pollution and many others, yet-to-be-conceived applications. The first part of Solution-Processable Components for Organic Electronic Devices covers the synthesis of: soluble conjugated polymers; solution-processable nanoparticles of inorganic semiconductors; high-k nanoparticles by means of controlled radical polymerization; advanced blending techniques yielding novel materials with extraordinary properties. The book also discusses photogeneration of charge carriers in nanostructured bulk heterojunctions and charge carrier transport in multicomponent materials such as composites and nanocomposites as well as photovoltaic devices modelling. The second part of the book is devoted to organic electronic devices, such as field effect transistors, light emitting diodes, photovoltaics, photodiodes and electronic memory devices which can be produced by solution-based methods, including printing and roll-to-roll manufacturing. The book provides in-depth knowledge for experienced researchers and for those entering the field. It comprises 12 chapters focused on: ? novel organic electronics components synthesis and solution-based processing techniques ? advanced analysis of mechanisms governing charge carrier generation and transport in organic semiconductors and devices ? fabrication techniques and characterization methods of organic electronic devices Providing coverage of the state of the art of organic electronics, Solution-Processable Components for Organic Electronic Devices is an excellent book for materials scientists, applied physicists, engineering scientists, and those working in the electronics industry.

Author: Xing-Hong Zhang
Publisher: John Wiley & Sons
ISBN: 3527823808
Category : Technology & Engineering
Languages : en
Pages : 482

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Book Description
A must-have resource to the booming field of sulfur-containing polymers Sulfur-Containing Polymers is a state-of-the-art text that offers a synthesis of the various sulfur-containing polymers from low-cost sulfur resources such as elemental sulfur, carbon disulfide (CS2), carbonyl sulfide (COS) and mercaptan. With contributions from noted experts on the topic, the book presents an in-depth understanding of the mechanisms related to the synthesis of sulfur-containing polymers. The book also includes a review of the various types of sulfur-containing polymers, such as: poly(thioester)s, poly(thioether)s and poly(thiocarbonate)s and poly(thiourethane)s with linear or hyperbranched (dendrimer) architectures. The expert authors provide the fundamentals on the structure-property relationship and applications of sulfur-containing polymers. Designed to be beneficial for both research and application-oriented chemists and engineers, the book contains the most recent research and developments of sulfur-containing polymers. This important book: Offers the first comprehensive handbook on the topic Contains state-of-the-art research on synthesis of sulfur containing polymers from low-cost sulfur-containing compounds Examines the synthesis, mechanism, structure properties, and applications of various types of sulful-containing polymers Includes contributions from well-known experts Written for polymer chemists, materials scientists, chemists in industry, biochemists, and chemical engineers, Sulfur-Containing Polymers offers a groundbreaking text to the field with inforamtion on the most recent research.

Author: Russell N. Grimes
Publisher: Academic Press
ISBN: 0128019050
Category : Science
Languages : en
Pages : 1060

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Book Description
Carboranes, Third Edition, by Russell Grimes, is the definitive resource on the subject. Completely updated with a wealth of research and review articles published in this active field since the previous volume was released in 2011, the book provides a readable and concise introduction to the basic principles underlying the synthesis, structures, and reactions of carboranes, heterocarboranes, and metallacarboranes. Following the valuable foundational information, the book explores the advances in practical applications for the many areas in which experts have discovered that carboranes afford new possibilities for solving problems and advancing the science. These disciplines include polymer science, catalysis, biomedicine, nanomaterials, and others. Winner of a 2017 Textbook Excellence Award (Texty) from the Textbook and Academic Authors Association Includes over 2,000 molecular structure drawings throughout the text Features expanded coverage on applications of carboranes, particularly in biomedicine and nanomaterials, given the growth of research in these areas Presents extended and updated tables, listing thousands of compounds with key literature references, provided online via the book’s website Explores the advances in practical applications for the many areas in which experts have discovered that carboranes afford new possibilities for solving problems and advancing the science

Author: Niyasi Serdar Sariciftci
Publisher: World Scientific
ISBN: 9814518212
Category : Science
Languages : en
Pages : 641

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Book Description
This volume concentrates on the controversy within the scientific community over how to explain, understand and describe the photophysics/photochemistry of this class of materials.This controvery is of such a fundamental nature that the solution of the problem might be in a unification of the semiconductor and metal physics with the molecular quantum chemistry. Thus, a wide-ranging and comprehensive discussion of this very crucial issue has not been written down yet.This volume brings together the most prominent scientists specializing in this controversial topic. Each contributor addresses the opponents' arguments. After short introductory chapters, the contributors discuss their own speciality area and compare the results with both models and explain their position on why one of the models is more appropriate. Special emphasis is given to comparative discussions with other conjugated molecular systems as well as inorganic semiconductors.