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Author: Tanmoy Dey Publisher: ISBN: Category : Electronic dissertations Languages : en Pages :
Book Description
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: Tanmoy Dey Publisher: ISBN: Category : Electronic dissertations Languages : en Pages :
Book Description
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: Venkataramanan Seshadri Publisher: ISBN: Category : Electronic dissertations Languages : en Pages :
Book Description
The first part of the work embodied in this thesis is towards modifying the electronic band-gap of conjugated polymers consisting of thieno[3,4- b]thiophene as one of the repeat units. Two different approaches were undertaken to prepare copolymers of thieno[3,4-b]thiophene in order to accomplish this. First, a simple simultaneous electropolymerization of two monomers from a solution mixture, and second, an oligomeric approach, wherein an oligomer of thiophene and thieno[3,4-b]thiophene with cyanovinylene spacer units was electrochemically polymerized. Several electroanalytical and spectroscopic techniques were used to characterize these polymers. The major part of the thesis is focused on the electrochromic properties of conjugated polymers both in liquid and solid-state electrochemical cells. Several polymers reported in literature were re-evaluated on the basis of its photopic transmissivity. It is necessary that the contrast in a device is more pronounced at wavelengths, wherein the human eye is most sensitive at a given time of the day. At the same time, it is also important to take into account that the eye is sensitive to a broad spectral range. Hence, this photopic approach is very essential in understanding how the intensity of light can be controlled using electrochromic windows. Furthermore, the optical switchability of solid-state electrochromic windows were also studied. Several issues, such as electrodeposition onto indium doped tinoxide (ITO) surfaces with areas ≥ 30cm2, device stability were addressed during the course of this research. The photopically weighted contrast of the device as a whole was found to be enhanced using derivatives of 3,4-propylenedioxythiophene, belonging to the 3,4-alkylenedioxythiophene family. Finally, new device architecture was studied, wherein very low band-gap conjugated polymer with little/no visible electrochromism was used as the ion-storage layer in a dual polymer configuration. Colorimetric analysis of these devices was compared with the earlier devices incorporating a high band-gap anodically coloring conjugated polymer and low band-gap cathodically coloring polymer. These devices were found to be switching between a deep blue to a sky blue, which is a neutral color, as opposed to deep blue to yellow in the earlier configuration. Yellow filter is known to alter the way colors are perceived by the human eye.
Author: Aubrey L. Dyer Publisher: ISBN: Category : Languages : en Pages :
Book Description
ABSTRACT: Chemistry Conjugated conducting polymers are among some of the most versatile materials to emerge in the past 20 years. They have been researched for applications that range from photovoltaics, to light-emitting diodes, electrochromic windows, actuators, and field effect transistors. This work details the analytical characterization of [pi]-conjugated polymers to understand their redox and optical properties, along with the development of several new types of devices that employ these polymers as the active materials for both variable optical attenuators and as dual electrochromic/electroluminescent displays. Within this work, a phenomenon that we term unsymmetrical switching has been uncovered for the first time in reflective electrochromic cells. The unsymmetrical switching in these displays is explored and a model devised to illustrate that the presence of a conductive front propagating through the polymer film on electrochemical oxidation is the contributing cause for this observation. For these experiments, a variety of analytical techniques have been utilized to characterize the devices and materials contained therein and include electrochemistry, spectroelectrochemistry, and photometry.
Author: Srabanti Ghosh Publisher: John Wiley & Sons ISBN: 3527345574 Category : Technology & Engineering Languages : en Pages : 38
Book Description
A timely overview of fundamental and advanced topics of conjugated polymer nanostructures Conjugated Polymer Nanostructures for Energy Conversion and Storage Applications is a comprehensive reference on conjugated polymers for energy applications. Distinguished academic and editor Srabanti Ghosh offers readers a broad overview of the synthesis, characterization, and energy-related applications of nanostructures based on conjugated polymers. The book includes novel approaches and presents an interdisciplinary perspective rooted in the interfacing of polymer and synthetic chemistry, materials science, organic chemistry, and analytical chemistry. This book provides complete descriptions of conjugated polymer nanostructures and polymer-based hybrid materials for energy conversion, water splitting, and the degradation of organic pollutants. Photovoltaics, solar cells, and energy storage devices such as supercapacitors, lithium ion battery electrodes, and their associated technologies are discussed, as well. Conjugated Polymer Nanostructures for Energy Conversion and Storage Applications covers both the fundamental topics and the most recent advances in this rapidly developing area, including: The design and characterization of conjugated polymer nanostructures, including the template-free and chemical synthesis of polymer nanostructures Conjugated polymer nanostructures for solar energy conversion and environmental protection, including the use of conjugated polymer-based nanocomposites as photocatalysts Conjugated polymer nanostructures for energy storage, including the use of nanocomposites as electrode materials The presentation of different and novel methods of utilizing conjugated polymer nanostructures for energy applications Perfect for materials scientists, polymer chemists, and physical chemists, Conjugated Polymer Nanostructures for Energy Conversion and Storage Applications also belongs on the bookshelves of organic chemists and any other practicing researchers, academics, or professionals whose work touches on these highly versatile and useful structures.
Author: Vijay Kumar Publisher: Woodhead Publishing ISBN: 0128240954 Category : Technology & Engineering Languages : en Pages : 443
Book Description
Conjugated Polymers for Next-Generation Applications, Volume Two: Energy Storage Devices describes the synthesis and characterization of varied conjugated polymeric materials and their key applications, including active electrode materials for electrochemical capacitors and lithium-ion batteries, along with new ideas of functional materials for next-generation high-energy batteries, a discussion of common design procedures, and the pros and cons of conjugated polymers for certain applications. The book’s emphasis lies in the underlying electronic properties of conjugated polymers, their characterization and analysis, and the evaluation of their effectiveness for utilization in energy and electronics applications. This book is ideal for researchers and practitioners in the area of materials science, chemistry and chemical engineering. Provides an overview of the synthesis and functionalization of conjugated polymers and their composites Reviews important photovoltaics applications of conjugated polymeric materials, including their use in energy storage, batteries and optoelectronic devices Discusses conjugated polymers and their application in electronics for sensing, bioelectronics, memory, and more
Author: Tanmoy Dey
Author: Tanmoy Dey
Author: Tanmoy Dey
Author: Venkataramanan Seshadri
Author: Aubrey L. Dyer
Author: Bryan D. Paulsen
Author: Srabanti Ghosh
Author: Vijay Kumar![Thermocleavable [pi]-conjugated Polymers PDF](https://books.google.com/books/content/images/frontcover/-AUGoQEACAAJ?fife=w80-h100)
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