| 1. |
- Bella, Federico, et al.
(författare)
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Caesium for Perovskite Solar Cells: An Overview
- 2018
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Ingår i: Chemistry - A European Journal. - : Wiley. - 1521-3765 .- 0947-6539. ; 24:47, s. 12183-12205
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Forskningsöversikt (refereegranskat)abstract
- Perovskite solar cells have the potential to revolutionize the world of photovoltaics, and their efficiency close to 23 % on a lab-scale recently certified this novel technology as the one with the most rapidly raising performance per year in the whole story of solar cells. With the aim of improving stability, reproducibility and spectral properties of the devices, in the last three years the scientific community strongly focused on Cs-doping for hybrid (typically, organolead) perovskites. In parallel, to further contrast hygroscopicity and reach thermal stability, research has also been carried out to achieve the development of all-inorganic perovskites based on caesium, the performances of which are rapidly increasing. The potential of caesium is further strengthened when it is used as a modifying agent of charge-carrier layers in solar cells, but also for the preparation of perovskites with peculiar optoelectronic properties for unconventional applications (e.g., in LEDs, photodetectors, sensors, etc.). This Review offers a 360-degree overview on how caesium can strongly tune the properties and performance of perovskites and relative perovskite-based devices.
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| 2. |
- Eriksson, Therese, 1992-
(författare)
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Cation Conduction and Coordination in Carbonyl-Containing Compounds : Li+ Transport in Alternative Polymer Electrolyte Host Materials
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The field of solid polymer electrolytes (SPEs) used to create safer lithium-ion batteries has been dominated by polyethylene oxide (PEO) since the discovery of its ion-conducting properties in the 1970s. In this thesis, as an alternative, the ion coordination and conduction properties of SPEs based on polyketones, polyesters and polycarbonates are investigated. Instead of having only an ether oxygen on the backbone (like PEO) the functional group in all three of these polymer classes contains a carbonyl oxygen, which is the main coordinating motif on the polymer backbone. The polyesters and polycarbonates do, however, have one or two more oxygens in the functional group compared to the polyketones. This was shown to have a great effect on the SPE properties. The key properties that have been studied in this work are the ionic conductivity, glass transition temperature, degree of crystallinity, coordination strength, and the transport number. The polymers are both studied individually and comparatively. The polyketone electrolytes studied in this thesis are novel to the solid polymer electrolyte field, and not as established as the polyesters and polycarbonates. The polyketone-based electrolytes have a high degree of crystallinity and the lithium coordination strength is quite high, therefore the ion transport is significantly reduced. Results with a higher salt concentration, however, suggest that with a more amorphous polyketone electrolyte, the transport properties could be significantly improved. The challenge with the polycarbonates is not the degree of crystallinity, as most of the ones studied herein are amorphous, but instead the high glass transition temperature. They are thereby restricted by the low degree of segmental motion present. This problem could not be solved by lowering the glass transition temperature by the addition of side-chains, as the side-chains instead block the pathway of the lithium ions. A positive aspect seen in the polycarbonate-based electrolytes was the high lithium transference number, which is significantly higher than both the polyketones’ and the polyester’s. The polyester is also semi-crystalline; the degree of crystallinity can be reduced by the addition of salt or nanoparticles though. Synthesising a polyester-polycarbonate copolymer is also an option to create an amorphous polymer. The polyester is somewhat of a midway between the polyketone and polycarbonate, both in its molecular structure as well as in its physical and ion transport properties. It does, however, show the highest ionic conductivity out of the three as it has a rather low glass transition temperature and not too strong ion coordination. This work highlights the physical, coordination and conduction properties found in carbonyl-containing polymer host materials. Even though the polyketones, polyesters and polycarbonates are structurally quite similar, their properties can vary significantly. They are, however, all likely candidates for tomorrow’s solid-state lithium-ion batteries.
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| 3. |
- Galliano, Simone, et al.
(författare)
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Hydrogel Electrolytes Based on Xanthan Gum : Green Route towards Stable Dye-Sensitized Solar Cells
- 2020
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Ingår i: Nanomaterials. - : MDPI AG. - 2079-4991. ; 10:8
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Tidskriftsartikel (refereegranskat)abstract
- The investigation of innovative electrolytes based on nontoxic and nonflammable solvents is an up-to-date, intriguing challenge to push forward the environmental sustainability of dye-sensitized solar cells (DSSCs). Water is one of the best choices, thus 100% aqueous electrolytes are proposed in this work, which are gelled with xanthan gum. This well-known biosourced polymer matrix is able to form stable and easily processable hydrogel electrolytes based on the iodide/triiodide redox couple. An experimental strategy, also supported by the multivariate chemometric approach, is used here to study the main factors influencing DSSCs efficiency and stability, leading to an optimized system able to improve its efficiency by 20% even after a 1200 h aging test, and reaching an overall performance superior to 2.7%. In-depth photoelectrochemical investigation demonstrates that DSSCs performance based on hydrogel electrolytes depends on many factors (e.g., dipping conditions, redox mediator concentrations, etc.), that must be carefully quantified and correlated in order to optimize these hydrogels. Photovoltaic performances are also extremely reproducible and stable in an open cell filled in air atmosphere, noticeably without any vacuum treatments.
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| 4. |
- Huiran, Lu, 1989-
(författare)
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Wood-based Materials for Lithium-ion Batteries
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Lithium-ion batteries (LIB) have become very important recently as power sources for portable electronics and electric vehicles. Today non-renewable petroleum-based polymers are used as binders in state-of-the-art LIB. Therefore, it is essential to investigate alternative binders, which are environmentally friendly and inexpensive. Using wood-based materials, such as cellulose and lignin, could make the batteries more environmentally benign, cheaper and easier to produce.Lignin, a byproduct from the pulping industry and the second most abundant bio-polymer in wood, has been investigated for the first time as binder material for eco-friendly LIB. Both LiFePO4 (LFP) positive and graphite negative electrodes using pretreated lignin as binder exhibited good electrochemical performance. The drawback of lignin as binder is that its poor mechanical properties limit the preparation of a thick electrode, constraining the energy density for LIB.In order to meet the demands of flexible and bendable electronic devices, cellulose nanofibrils (CNF) as binder materials have been successfully fabricated for flexible batteries by a water-based paper making process. It showed excellent binding properties for different kinds of electrode materials, which were homogenously dispersed in its visible network. The flexible electrodes obtained good mechanical and electrochemical properties. A study of different CNF shows that the manufacturing process affects the performance of the electrodes.Another innovative LIB concept in this thesis was to build both lightweight and bendable LIB. Chopped carbon fibers (CF), bound by CNF, were demonstrated as both current collector and as a current collector-free negative electrode, produced by an easy filtration process. The gravimetric energy density was increased compared to cells with metallic current collectors. The CF-based lightweight and flexible electrode achieved a good cycling stability, rate capability, even after 4000 times of bending.
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