| 1. |
- Willfahrt, Andreas, 1977-
(författare)
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Screen Printing Technology for Energy Devices
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The technical application of screen and stencil printing has been state of the art for decades. As part of the subtractive production process of printed circuit boards, for instance, screen and stencil printing play an important role. With the end of the 20th century, another field has opened up with organic electronics. Since then, more and more functional layers have been produced using printing methods. Printed electronics devices offer properties that give almost every freedom to the creativity of product development. Flexibility, low weight, use of non-toxic materials, simple disposal and an enormous number of units due to the production process are some of the prominent keywords associated with this field.Screen printing is a widely used process in printed electronics, as this process is very flexible with regard to the materials that can be used. In addition, a minimum resolution of approximately 30 µm is sufficiently high. The ink film thickness, which can be controlled over a wide range, is an extremely important advantage of the process. Depending on the viscosity, layer thicknesses of several hundred nanometres up to several hundred micrometres can be realised.The conversion and storage of energy became an increasingly important topic in recent years. Since regenerative energy sources, such as photovoltaics or wind energy, often supply energy intermittently, appropriate storage systems must be available. This applies to large installations for the power supply of society, but also in the context of autarkic sensors, such as those used in the Internet of Things or domestic/industrial automation. A combination of micro-energy converters and energy storage devices is an adequate concept for providing energy for such applications.In this thesis the above mentioned keywords are addressed and the feasibility of printed thermoelectric energy converters and supercapacitors as energy storage devices are investigated. The efficiency of thermoelectric generators (TEG) is low, but in industrial environments, for example, a large amount of unused low temperature heat energy can be found. If the production costs of TEGs are low, conversion of this unused heat energy can contribute to increasing system efficiency.Additionally, printing of supercapacitor energy storage devices increases the usability of the TEG. It is appropriate to use both components as complementary parts in an energy system.
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| 2. |
- Che, Canyan, 1988-
(författare)
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Electrochemical Reactions of Quinones at Conducting Polymer Electrodes
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Proton-coupled multielectron transfer reactions are of great abundance in Nature. In particular, two-proton-two-electron transfers in quinone/hydroquinone redox couples are behind oxidative phosphorylation (ADP-to-ATP) and photosystem II. The redox processes of neurotransmitters, as a platform for brain activity read-out, are two-proton two-electron transfers of quinones. Moreover, humic acids, which constitute a major organic fraction of soil, turf, coal, and lignin, which forms as a large-scale surplus product from forest and paper industry, contain a large quantity of polyphenols, which can undergo the exchange of two electrons per aromatic ring accompanied with transfers of two protons. This makes polyphenol-based biopolymers, such as lignin, promising green-chemistry renewable materials for electrical energy storage or generation. The application of intact or depolymerized polyphenols in electrical energy devices such as fuel cells and redox flow batteries requires appropriate electrode materials to ensure efficient proton-coupled electron transfer reactions occurring at the solid-liquid interface. Moreover, investigation of the biological quinones reaction calls for porous, soft, biocompatible materials as implantable devices to reduce the rejection reaction and pain.At common electrode materials such as platinum and carbons, quinone/hydroquinone redox processes are rather irreversible; in addition, platinum is very costly. Conducting polymers (CPs), poly(3,4-ethylenedioxythiophene) (PEDOT) in particular, offer an attractive option as metal-free electrode material for these reactions due to their molecular porosity, high electrical and ionic conductivity, solution processability, resistance to acid media, as well as high atomic abundance of their constituents.This thesis explores the possibility of utilizing CPs as electrode materials for driving various quinone redox reactions. Firstly, we studied the electrocatalytic activity and mechanism of PEDOTs for the generic hydroquinone reaction and their application in a fuel cell. Secondly, the mechanism of integrating lignosulfonate (LS) into CP matrices and optimization strategies were explored in order to boost energy storage capacity. Thirdly, we attained mechanistic understanding of the influence of ionic transport and proton management on the thermodynamics and kinetics of the electrocatalysis on CPs, thereby providing steps towards the design of quinone-based electrical energy storage devices, such as organic redox flow batteries (ORFB).
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| 3. |
- Han, Shaobo, 1988-
(författare)
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Thermoelectric polymer-cellulose composite aerogels
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Thermoelectric materials are scrutinized as energy materials and sensing materials. Indeed, they convert thermal energy into electrical energy. In addition, those materials are actively sensitive to a temperature modification through the generation of an electric signal. Organic thermoelectric (OTE) materials are complementary to inorganic thermoelectric materials, as they possess unique properties such as solution processing, ionic conductivity, flexibility, and softness. While thin-film OTE materials have been widely studied because they are easily manufactured by various coating techniques, little is done in the creation of three-dimensional morphologies of OTE materials; which is important to develop large temperature gradients.Cellulose is the most abundant biopolymer on the planet. Recently, the applications of cellulose are not only limited in making papers but also in electronics as the cellulose provide 3-D microstructures and mechanical strength. One promising approach to make 3-D OTE bulks is using cellulose as scaffold because of their properties of relatively high mechanical strength, water processability and environmentally friendly performance.The aims of the thesis have been to enlarge the applications of an OTE material poly(3,4-ethylenedioxythiophene) (PEDOT), with an approach of making 3-D aerogels composite with nanofibrillated cellulose (NFC), in two main areas: (1) multi-parameter sensors and (2) solar vapor generators. In the first application, we demonstrate that the new thermoelectric aerogel responds independently to pressure P, temperature T and humidity RH. Hence, when it is submitted to the three stresses (T, P, RH), the electrical characterization of the material enables to measure the three parameters without cross-talking effects. Thermoelectric aerogels are foreseen as active materials in electronic skins and robotics. In the second application, the conducting polymer aerogels are employed as solar absorbers to convert solar energy into heat and significantly increased the water evaporation rate. The IR absorption is efficient because of the free-electron in the conducting polymer PEDOT nano-aggregates. Because of the low cost of those materials and the water stability of the crosslinked aerogels, they could be of importance for water desalination.
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| 4. |
- Che, Canyan, 1988-, et al.
(författare)
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Twinning Lignosulfonate with a Conducting Polymer via Counter-Ion Exchange for Large-Scale Electrical Storage
- 2019
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Ingår i: Advanced Sustainable Systems. - : Wiley-VCH Verlag. - 2366-7486. ; 3:9
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Tidskriftsartikel (refereegranskat)abstract
- Lignosulfonate (LS) is a large-scale surplus product of the forest and paper industries, and has primarily been utilized as a low-cost plasticizer in making concrete for the construction industry. LS is an anionic redox-active polyelectrolyte and is a promising candidate to boost the charge capacity of the positive electrode (positrode) in redox-supercapacitors. Here, the physical-chemical investigation of how this biopolymer incorporates into the conducting polymer PEDOT matrix, of the positrode, by means of counter-ion exchange is reported. Upon successful incorporation, an optimal access to redox moieties is achieved, which provides a 63% increase of the resulting stored electrical charge by reversible redox interconversion. The effects of pH, ionic strength, and concentrations, of included components, on the polymer–polymer interactions are optimized to exploit the biopolymer-associated redox currents. Further, the explored LS-conducting polymer incorporation strategy, via aqueous synthesis, is evaluated in an up-scaling effort toward large-scale electrical energy storage technology. By using an up-scaled production protocol, integration of the biopolymer within the conducting polymer matrix by counter-ion exchange is confirmed and the PEDOT-LS synthesized through optimized strategy reaches an improved charge capacity of 44.6 mAh g−1.
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| 5. |
- Fahlman, Mats, 1967-, et al.
(författare)
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Interfaces in organic electronics
- 2019
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Ingår i: Nature Reviews Materials. - : Nature Publishing Group. - 2058-8437. ; 4:10, s. 627-650
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Forskningsöversikt (refereegranskat)abstract
- Undoped, conjugated, organic molecules and polymers possess properties of semiconductors, including the electronic structure and charge transport, which can be readily tuned by chemical design. Moreover, organic semiconductors (OSs) can be n-doped or p-doped to become organic conductors and can exhibit mixed electronic and ionic conductivity. Compared with inorganic semiconductors and metals, organic (semi)conductors possess a unique feature: no insulating oxide forms on their surface when exposed to air. Thus, OSs form clean interfaces with many materials, including metals and other OSs. OS–metal and OS–OS interfaces have been intensely investigated over the past 30 years, from which a consistent theoretical description has emerged. Since the 2000s, increased attention has been paid to interfaces in organic electronics that involve dielectrics, electrolytes, ferroelectrics and even biological organisms. In this Review, we consider the central role of these interfaces in the function of organic electronic devices and discuss how the physico-chemical properties of the interfaces govern the interfacial transport of light, excitons, electrons and ions, as well as the transduction of electrons into the molecular language of cells.
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| 6. |
- Kim, Nara, 1985-, et al.
(författare)
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Electric transport properties in PEDOT thin films
- 2019. - 4
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Ingår i: Conjugated polymers. - Boca Raton : CRC Press. - 9780429190520 ; , s. 45-128
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Bokkapitel (refereegranskat)abstract
- In this chapter, the authors summarize their understanding of Poly(3,4-ethylenedioxythiophene) (PEDOT), with respect to its chemical and physical fundamentals. They focus upon the structure of several PEDOT systems, from the angstrom level and up, and the impact on both electronic and ionic transport. The authors discuss the structural properties of PEDOT:X and PEDOT:poly(styrenesulfonate) based on experimental data probed at the scale ranging from angstrom to submicrometer. The morphology of PEDOT is influenced by the nature of counter-ions, especially at high oxidation levels. The doping anions intercalate between PEDOT chains to form a “sandwich” structure to screen the positive charges in PEDOT chains. The authors provide the main transport coefficients such as electrical conductivity s, Seebeck coefficient S, and Peltier coefficient σ, starting from a general thermodynamic consideration. The optical conductivity of PEDOT has also been examined based on the effective medium approximation, which is normally used to describe microscopic permittivity properties of composites made from several different constituents.
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| 7. |
- Mitraka, Evangelia, 1986-, et al.
(författare)
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Electrocatalytic Production of Hydrogen Peroxide with Poly(3,4-ethylenedioxythiophene) Electrodes
- 2019
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Ingår i: Advanced Sustainable Systems. - : Wiley-VCH Verlagsgesellschaft. - 2366-7486 .- 2366-7486. ; 3:2, s. 1-6
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Tidskriftsartikel (refereegranskat)abstract
- Electrocatalysis for energy‐efficient chemical transformations is a central concept behind sustainable technologies. Numerous efforts focus on synthesizing hydrogen peroxide, a major industrial chemical and potential fuel, using simple and green methods. Electrochemical synthesis of peroxide is a promising route. Herein it is demonstrated that the conducting polymer poly(3,4‐ethylenedioxythiophene), PEDOT, is an efficient and selective heterogeneous catalyst for the direct reduction of oxygen to hydrogen peroxide. While many metallic catalysts are known to generate peroxide, they subsequently catalyze decomposition of peroxide to water. PEDOT electrodes can support continuous generation of high concentrations of peroxide with Faraday efficiency remaining close to 100%. The mechanisms of PEDOT‐catalyzed reduction of O2 to H2O2 using in situ spectroscopic techniques and theoretical calculations, which both corroborate the existence of a chemisorbed reactive intermediate on the polymer chains that kinetically favors the selective reduction reaction to H2O2, are explored. These results offer a viable method for peroxide electrosynthesis and open new possibilities for intrinsic catalytic properties of conducting polymers.
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| 8. |
- Zhao, Dan, 1986-, et al.
(författare)
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Polymer gels with tunable ionic Seebeck coefficient for ultra-sensitive printed thermopiles
- 2019
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- Measuring temperature and heat flux is important for regulating any physical, chemical, and biological processes. Traditional thermopiles can provide accurate and stable temperature reading but they are based on brittle inorganic materials with low Seebeck coefficient, and are difficult to manufacture over large areas. Recently, polymer electrolytes have been proposed for thermoelectric applications because of their giant ionic Seebeck coefficient, high flexibility and ease of manufacturing. However, the materials reported to date have positive Seebeck coefficients, hampering the design of ultra-sensitive ionic thermopiles. Here we report an “ambipolar” ionic polymer gel with giant negative ionic Seebeck coefficient. The latter can be tuned from negative to positive by adjusting the gel composition. We show that the ion-polymer matrix interaction is crucial to control the sign and magnitude of the ionic Seebeck coefficient. The ambipolar gel can be easily screen printed, enabling large-area device manufacturing at low cost.
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