Doping And Density Of States Engineering For Organic Thermoelectrics
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Doping And Density Of States Engineering For Organic Thermoelectrics
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Author : Guangzheng Zuo
language : en
Publisher: Linköping University Electronic Press
Release Date : 2018-05-14
Doping And Density Of States Engineering For Organic Thermoelectrics written by Guangzheng Zuo and has been published by Linköping University Electronic Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018-05-14 with categories.
Thermoelectric materials can turn temperature differences directly into electricity. To use this to harvest e.g. waste heat with an efficiency that approaches the Carnot efficiency requires a figure of merit ZT larger than 1. Compared with their inorganic counterparts, organic thermoelectrics (OTE) have numerous advantages, such as low cost, large-area compatibility, flexibility, material abundance and an inherently low thermal conductivity. Therefore, organic thermoelectrics are considered by many to be a promising candidate material system to be used in lower cost and higher efficiency thermoelectric energy conversion, despite record ZT values for OTE currently lying around 0.25. A complete organic thermoelectric generator (TEG) normally needs both p-type and n-type materials to form its electric circuit. Molecular doping is an effective way to achieve p- and ntype materials using different dopants, and it is necessary to fundamentally understand the doping mechanism. We developed a simple yet quantitative analytical model and compare it with numerical kinetic Monte Carlo simulations to reveal the nature of the doping effect. The results show the formation of a deep tail in the Gaussian density of states (DOS) resulting from the Coulomb potentials of ionized dopants. It is this deep trap tail that negatively influences the charge carrier mobility with increasing doping concentration. The trends in mobilities and conductivities observed from experiments are in good agreement with the modeling results, for a large range of materials and doping concentrations. Having a high power factor PF is necessary for efficient TEG. We demonstrate that the doping method can heavily impact the thermoelectric properties of OTE. In comparison to conventional bulk doping, sequential doping can achieve higher conductivity by preserving the morphology, such that the power factor can improve over 100 times. To achieve TEG with high output power, not only a high PF is needed, but also having a significant active layer thickness is very important. We demonstrate a simple way to fabricate multi-layer devices by sequential doping without significantly sacrificing PF. In addition to the application discussed above, harvesting large amounts of heat at maximum efficiency, organic thermoelectrics may also find use in low-power applications like autonomous sensors where voltage is more important than power. A large output voltage requires a high Seebeck coefficient. We demonstrate that density of states (DOS) engineering is an effective tool to increase the Seebeck coefficient by tailoring the positions of the Fermi energy and the transport energy in n- and p-type doped blends of conjugated polymers and small molecules. In general, morphology heavily impacts the performance of organic electronic devices based on mixtures of two (or more) materials, and organic thermoelectrics are no exception. We experimentally find that the charge and energy transport is distinctly different in well-mixed and phase separated morphologies, which we interpreted in terms of a variable range hopping model. The experimentally observed trends in conductivity and Seebeck coefficient are reproduced by kinetic Monte Carlo simulations in which the morphology is accounted for.
Doping And Density Of States Engineering For Organic Thermoelectrics
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Author : Guangzheng Zuo
language : en
Publisher:
Release Date : 2018
Doping And Density Of States Engineering For Organic Thermoelectrics written by Guangzheng Zuo and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018 with categories.
Thermoelectric materials can turn temperature differences directly into electricity. To use this to harvest e.g. waste heat with an efficiency that approaches the Carnot efficiency requires a figure of merit ZT larger than 1. Compared with their inorganic counterparts, organic thermoelectrics (OTE) have numerous advantages, such as low cost, large-area compatibility, flexibility, material abundance and an inherently low thermal conductivity. Therefore, organic thermoelectrics are considered by many to be a promising candidate material system to be used in lower cost and higher efficiency thermoelectric energy conversion, despite record ZT values for OTE currently lying around 0.25. A complete organic thermoelectric generator (TEG) normally needs both p-type and n-type materials to form its electric circuit. Molecular doping is an effective way to achieve p- and ntype materials using different dopants, and it is necessary to fundamentally understand the doping mechanism. We developed a simple yet quantitative analytical model and compare it with numerical kinetic Monte Carlo simulations to reveal the nature of the doping effect. The results show the formation of a deep tail in the Gaussian density of states (DOS) resulting from the Coulomb potentials of ionized dopants. It is this deep trap tail that negatively influences the charge carrier mobility with increasing doping concentration. The trends in mobilities and conductivities observed from experiments are in good agreement with the modeling results, for a large range of materials and doping concentrations. Having a high power factor PF is necessary for efficient TEG. We demonstrate that the doping method can heavily impact the thermoelectric properties of OTE. In comparison to conventional bulk doping, sequential doping can achieve higher conductivity by preserving the morphology, such that the power factor can improve over 100 times. To achieve TEG with high output power, not only a high PF is needed, but also having a significant active layer thickness is very important. We demonstrate a simple way to fabricate multi-layer devices by sequential doping without significantly sacrificing PF. In addition to the application discussed above, harvesting large amounts of heat at maximum efficiency, organic thermoelectrics may also find use in low-power applications like autonomous sensors where voltage is more important than power. A large output voltage requires a high Seebeck coefficient. We demonstrate that density of states (DOS) engineering is an effective tool to increase the Seebeck coefficient by tailoring the positions of the Fermi energy and the transport energy in n- and p-type doped blends of conjugated polymers and small molecules. In general, morphology heavily impacts the performance of organic electronic devices based on mixtures of two (or more) materials, and organic thermoelectrics are no exception. We experimentally find that the charge and energy transport is distinctly different in well-mixed and phase separated morphologies, which we interpreted in terms of a variable range hopping model. The experimentally observed trends in conductivity and Seebeck coefficient are reproduced by kinetic Monte Carlo simulations in which the morphology is accounted for.
Organic Thermoelectric Materials
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Author : Zhiqun Lin
language : en
Publisher: Royal Society of Chemistry
Release Date : 2019-10-18
Organic Thermoelectric Materials written by Zhiqun Lin and has been published by Royal Society of Chemistry this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019-10-18 with Science categories.
Thermoelectric materials have received a great deal of attention in energy-harvesting and cooling applications, primarily due to their intrinsic low cost, energy efficient and eco-friendly nature. The past decade has witnessed heretofore-unseen advances in organic-based thermoelectric materials and devices. This title summarises the significant progress that has been made in the molecular design, physical characterization, and performance optimization of organic thermoelectric materials, focusing on effective routes to minimize thermal conductivity and maximize power factor. Featuring a series of state-of-the-art strategies for enhancing the thermoelectric figure of merit (ZT) of organic thermoelectricity, and highlighting cutting-edge concepts to promote the performance of organic thermoelectricity, chapters will strengthen the exploration of new high-ZT thermoelectric materials and their potential applications. With contributions from leading worldwide authors, Organic Thermoelectric Materials will appeal to graduate students as well as academic and industrial researchers across chemistry, materials science, physics and engineering interested in the materials and their applications.
Organic Thermoelectric Materials
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Author : Zhiqun Lin
language : en
Publisher: Royal Society of Chemistry
Release Date : 2019-10-18
Organic Thermoelectric Materials written by Zhiqun Lin and has been published by Royal Society of Chemistry this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019-10-18 with Science categories.
This book summarises the significant progress made in organic thermoelectric materials, focusing on effective routes to minimize thermal conductivity and maximize power factor.
Organic Thermoelectrics
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Author : Daoben Zhu
language : en
Publisher: John Wiley & Sons
Release Date : 2022-11-03
Organic Thermoelectrics written by Daoben Zhu and has been published by John Wiley & Sons this book supported file pdf, txt, epub, kindle and other format this book has been release on 2022-11-03 with Technology & Engineering categories.
Organic Thermoelectrics Enables readers to understand the development and applications of organic thermoelectric conversion, including fundamentals and experimental breakthroughs Organic Thermoelectrics: From Materials to Devices introduces organic thermoelectric materials to devices in a systematic manner, covering the development of organic thermoelectric materials, followed by a discussion on the fundamental mechanism of thermoelectric conversion, design strategy, and advances in different materials, device fabrication, and characterizations of thermoelectric parameters. In Organic Thermoelectrics: From Materials to Devices, readers can expect to find detailed information on: Fundamentals of thermoelectric (TE) conversion, development of organic thermoelectric (OTE) fields and mechanisms, and basic physical processes in carrier transport and thermal transport for TE conversion Recent development and key strategies to develop p-type, n-type, and composite/hybrid OTE materials Basic mechanisms, fundamental requirements, and recent advances of doping for OTE applications, plus geometries and construction methods of OTE devices Theoretical and experimental advances in single molecular TE devices, together with the recent development in related detection methods Powered by worldwide innovative research results in the past ten years and strongly supported by many collaborators, Organic Thermoelectrics is a comprehensive reference on the subject and is invaluable for scientists and students in chemistry, materials, and engineering.
Innovative Thermoelectric Materials Polymer Nanostructure And Composite Thermoelectrics
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Author : Howard E Katz
language : en
Publisher: World Scientific
Release Date : 2016-01-22
Innovative Thermoelectric Materials Polymer Nanostructure And Composite Thermoelectrics written by Howard E Katz and has been published by World Scientific this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016-01-22 with Science categories.
Power generation from environmentally friendly sources has led to surging interest in thermoelectrics. There has been a move toward alternative thermoelectric materials with enhanced performance through materials and structures that utilize common and safer elements and alternative mechanistic approaches while increasing processing latitude and decreasing cost. This wide-ranging volume examines this progress and future prospects with the new technologies, ease of processing and cost as major considerations, and will benefit active researchers, students and others interested in cutting-edge work in thermoelectric materials. Innovative Thermoelectric Materials incorporates the contributions of a group of recognized experts in thermoelectric materials, many of whom were the first to introduce various materials systems into thermoelectric systems. The perspectives brought to this evolving subject will provide important insights on which those developing the field can build, and will inspire new research directions for the future.
Impact Of Chemical Doping On The Thermoelectric Charge Transport Of Organic Semiconductors
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Author : Connor J. Boyle
language : en
Publisher:
Release Date : 2018
Impact Of Chemical Doping On The Thermoelectric Charge Transport Of Organic Semiconductors written by Connor J. Boyle and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018 with categories.
The thermoelectric properties of organic semiconductors allow them to directly convert heat into electricity without the use of moving parts and to directly convert electricity into heat without the use of working fluids. These properties offer opportunities for the generation of electricity from non-conventional or renewable sources of heat and for refrigeration without the risk of leaking harmful working fluids at any length scale down to the nanoscale. Since organic materials are lightweight, flexible, and made from abundant resources, these opportunities could one day become affordable for widespread use and could be expanded to include specialized and otherwise difficult to reach applications, such as wearable refrigeration and electricity generation from anthropogenic heat. Since these properties are a result of how charge carriers in organic materials transfer energy upon conduction, measuring these properties also allows us to better understand the factors that influence how charge carriers carry energy during charge transport. One of the remaining challenges in developing organic thermoelectric materials for practical use is the preparation of n-type thermoelectric materials, which transport electrons as their charge carrier, since most n-type organic semiconductors are unstable in air due to electron transfer to oxygen gas. We synthesized three organic conjugated polymers based on electron deficient rylene diimides and a vinylene spacer - PDNDIV, PFNDIV, and PDIV - to study how these could be doped into n-type semiconductors and how long these persist in air. Each polymer was capable of electron transport, and PFNDIV was capable of remaining n-doped with electronic charges for at least one week in air. Blending conducting fillers into organic thermoelectric materials can alter their thermoelectric properties by altering the mechanism of charge transport. We blended the conductive filler SWNT into the organic conjugated polymer PBTDV2 and measured the thermoelectric properties. Although PBTDV2 was originally developed for use as an electron transporting polymer, all blends of SWNT with PBTDV2 had p-type, hole transporting, thermoelectric properties similar to those of oxygen-doped SWNT. We measured the thermoelectric properties of two p-type organic polymers - P3HT and PDPP4T - that were doped to achieve a high concentration of charge carriers as they spontaneously de-doped and decreased their charge carrier concentration. Modeling these thermoelectric properties revealed that the spatial distribution of dopants in the polymers impacted the how much energy was carried per charge carrier due to Coulombic interactions of the dopants with the charge carriers, and that more heterogeneous spatial distributions of dopants can limit the thermoelectric performance by limiting how much energy is carried per charge carrier. These findings aid in the future development of organic thermoelectric materials by highlighting the importance of doping organic thermoelectric materials in ways that achieve homogeneous spatial distributions of dopants.
Thermoelectric Materials And Devices
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Author : Iris Nandhakumar
language : en
Publisher: Royal Society of Chemistry
Release Date : 2017
Thermoelectric Materials And Devices written by Iris Nandhakumar and has been published by Royal Society of Chemistry this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with Science categories.
Authoritative account of recent developments in thermoelectric materials and devices for power energy harvesting applications, ideal for researchers and industrialists in materials science.
Introduction To Thermoelectricity
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Author : H. Julian Goldsmid
language : en
Publisher: Springer Science & Business Media
Release Date : 2009-10-03
Introduction To Thermoelectricity written by H. Julian Goldsmid and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2009-10-03 with Science categories.
Introduction to Thermoelectricity is the latest work by Professor Julian Goldsmid drawing on his 55 years experience in the field. The theory of the thermoelectric and related phenomena is presented in sufficient detail to enable researchers to understand their observations and develop improved thermoelectric materials. The methods for the selection of materials and their improvement are discussed. Thermoelectric materials for use in refrigeration and electrical generation are reviewed. Experimental techniques for the measurement of properties and for the production of thermoelements are described. Special emphasis is placed on nanotechnology which promises to yield great improvements in the efficiency of thermoelectric devices. Chapters are also devoted to transverse thermoelectric effects and thermionic energy conversion, both techniques offering the promise of important applications in the future.
Molecular Doping Of Organic Semiconductors
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Author : Torben Menke
language : de
Publisher:
Release Date : 2013
Molecular Doping Of Organic Semiconductors written by Torben Menke and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with categories.
