| 1. |
- Kiefer, David, 1989, et al.
(författare)
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Enhanced n-Doping Efficiency of a Naphthalenediimide-Based Copolymer through Polar Side Chains for Organic Thermoelectrics
- 2018
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Ingår i: ACS Energy Letters. - : American Chemical Society (ACS). - 2380-8195. ; 3:2, s. 278-285
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Tidskriftsartikel (refereegranskat)abstract
- N-doping of conjugated polymers either requires a high dopant fraction or yields a low electrical conductivity because of their poor compatibility with molecular dopants. We explore n-doping of the polar naphthalenediimide–bithiophene copolymer p(gNDI-gT2) that carries oligoethylene glycol-based side chains and show that the polymer displays superior miscibility with the benzimidazole–dimethylbenzenamine-based n-dopant N-DMBI. The good compatibility of p(gNDI-gT2) and N-DMBI results in a relatively high doping efficiency of 13% for n-dopants, which leads to a high electrical conductivity of more than 10–1 S cm–1 for a dopant concentration of only 10 mol % when measured in an inert atmosphere. We find that the doped polymer is able to maintain its electrical conductivity for about 20 min when exposed to air and recovers rapidly when returned to a nitrogen atmosphere. Overall, solution coprocessing of p(gNDI-gT2) and N-DMBI results in a larger thermoelectric power factor of up to 0.4 μW K–2 m–1 compared to other NDI-based polymers.
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| 2. |
- Hofmann, Anna, 1987, et al.
(författare)
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Doping and processing of organic semiconductors for plastic thermoelectrics
- 2018
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Ingår i: Handbook of Organic Materials for Electronic and Photonic Devices, Second Edition. - 9780081022849 ; , s. 429-449
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Thermoelectrics currently attracts considerable attention as a promising branch in the field of organic electronics, with the prospect that organic semiconductors (OSCs) allow the development of light, flexible, and inexpensive thermoelectric devices, which act as alternative power sources, generating electricity from heat gradients. Thermoelectric generators are solid-state devices that convert heat directly to electricity. They do not contain any moving parts and are able to operate over an extended period of time, and furthermore can function with small heat sources and limited temperature differences, which facilitates their use in situations where traditional engines are not feasible. The absence of moving parts, low need for maintenance, and a large variety of possible device architectures render organic thermoelectrics attractive for numerous applications, ranging from waste heat recovery to wearable textiles. In this chapter, we give a short introduction to the fundamentals of the thermoelectric effect, as well as to the design principles for thermoelectric generators and their characterization. Furthermore, we discuss the role of doping (i.e., the introduction of charge carriers through the addition of dopant molecules) and of the nanostructure and present strategies for the optimization of the thermoelectric properties of OSCs. Finally, we give an overview of processing methods and point out major achievements, as well as the remaining challenges.
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| 3. |
- Hofmann, Anna, 1987, et al.
(författare)
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Highly stable doping of a polar polythiophene through co-processing with sulfonic acids and bistriflimide
- 2018
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Ingår i: Journal of Materials Chemistry C. - : Royal Society of Chemistry (RSC). - 2050-7534 .- 2050-7526. ; 6:26, s. 6905-6910
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Tidskriftsartikel (refereegranskat)abstract
- Doping of organic semiconductors is currently an intensely studied field, since it is a powerful tool to optimize the performance of various organic electronic devices, ranging from organic solar cells, to thermoelectric modules, and bio-medical sensors. Despite recent advances, there is still a need for the development of highly conducting polymer: dopant systems with excellent long term stability and a high resistance to elevated temperatures. In this work we study the doping of the polar polythiophene derivative p(g(4)2T-T) by various sulfonic acids and bistriflimide via different processing techniques. We demonstrate that simple co-processing of p(g(4)2T-T) with an acid dopant yields conductivities of up to 120 S cm(-1), which remain stable for more than six months under ambient conditions. Notably, a high conductivity is only achieved if the doping is carried out in air, which can be explained with a doping process that involves an acid mediated oxidation of the polymer through O-2. P(g(4)2T-T) doped with the non-toxic and inexpensive 1,3-propanedisulfonic acid was found to retain its electrical conductivity for at least 20 hours upon annealing at 120 degrees C, which allowed the bulk processing of the doped polymer into conducting, free-standing and flexible films and renders the di-acid a promising alternative to commonly used redox dopants.
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| 4. |
- Hofmann, Anna, 1987, et al.
(författare)
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Materials for Transparent Electrodes: From Metal Oxides to Organic Alternatives
- 2018
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Ingår i: Advanced Electronic Materials. - : Wiley. - 2199-160X .- 2199-160X. ; 4:10
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Forskningsöversikt (refereegranskat)abstract
- Optoelectronic devices, such as displays, are now omnipresent in our daily life. A crucial component of these devices is a transparent electrode, which allows the in- and outcoupling of light. With the goal of optimizing the electrode characteristics and improving device efficiencies, many approaches for the fabrication of thin, transparent, conducting films have been studied. This review gives an overview of the different material classes which are used as transparent electrodes, ranging from metal oxides, such as indium tin oxide, metal, and carbonaceous nanostructures, to conducting polymers and composites. For every material class, a brief description of the fundamental principles, processing routes, and the latest achievements is given. Furthermore, the optoelectronic performance, flexibility, and surface roughness of the different electrodes are compared. Ultimately, advantages and drawbacks of the respective electrodes are discussed. This critical comparison of fundamentally different transparent conducting materials allows, on one hand, to make a sensible choice of electrode for specific applications, and, on the other hand, to point out scientific challenges that must still be addressed.
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