| 1. |
- Ajjan, Fátima, et al.
(författare)
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Spectroelectrochemical investigation of redox states in a polypyrrole/lignin composite electrode material
- 2015
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Ingår i: Journal of Materials Chemistry A. - : ROYAL SOC CHEMISTRY. - 2050-7488 .- 2050-7496. ; 3:24, s. 12927-12937
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Tidskriftsartikel (refereegranskat)abstract
- We report spectroelectrochemical studies to investigate the charge storage mechanism of composite polypyrrole/lignin electrodes. Renewable bioorganic electrode materials were produced by electropolymerization of pyrrole in the presence of a water-soluble lignin derivative acting as a dopant. The resulting composite exhibited enhanced charge storage abilities due to a lignin-based faradaic process, which was expressed after repeated electrochemical redox of the material. The in situ FTIR spectroelectrochemistry results show the formation of quinone groups, and reversible oxidation-reduction of these groups during charge-discharge experiments in the electrode materials. The most significant IR bands include carbonyl absorption near 1705 cm(-1), which is attributed to the creation of quinone moieties during oxidation, and absorption at 1045 cm(-1) which is due to hydroquinone moieties.
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| 2. |
- Fernandez-Benito, Amparo, et al.
(författare)
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Green and Scalable Biopolymer-Based Aqueous Polyelectrolyte Complexes for Zinc-Ion Charge Storage Devices
- 2023
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Ingår i: ChemElectroChem. - : WILEY-V C H VERLAG GMBH. - 2196-0216. ; 10:2
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Tidskriftsartikel (refereegranskat)abstract
- Green and scalable materials are essential to fulfill the need of electrification for transitioning into a fossil-fuels free society, and sustainability is a requirement for all new technologies. Rechargeable batteries are one of the most important elements for electrification, enabling the transition to mobile electronics, electrical vehicles and grid storage. We here report synthesis and characterization of polyelectrolyte complexes of alginate and chitosan, both biopolymers deriving from the sea, for transport of zinc ions in hydrogel electrolytes. We have used vibrational spectroscopy, thermal measurements and microscopy, as well as transport measurements with ohmic or blocking contacts. The transference number for zinc ions is close to 1, the conductivity is approximate to 10 mS/cm, with stability at Zn interfaces seen through 7000 cycles in symmetric zinc//zinc cell. A zinc ion aqueous electrolyte was prepared from blends of chitosan and alginate, by using a simple and scalable route. These green zinc ion electrolytes exhibit a stability window up to 2 V, a zinc ion transference number close to 1, and electrochemical cyclability over 7000 cycles at interfaces to zinc. This biologically derived polyelectrolyte complex offers many possibilities for optimizing transport and stability at electrode interfaces.image
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| 3. |
- Ouyang, Liangqi, et al.
(författare)
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Imaging the Phase Separation Between PEDOT and Polyelectrolytes During Processing of Highly Conductive PEDOT:PSS Films
- 2015
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Ingår i: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 7:35, s. 19764-19773
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Tidskriftsartikel (refereegranskat)abstract
- Treating PEDOT:PSS (Clevios) with certain additives, such as ethylene glycol (EG), dimethyl sulfoxide (DMSO) and sorbitol, has been shown to increase the conductivity of this material from roughly 1 to nearly 1000 S/cm. Using a slow drying method, we show that the additive induced a separation between free PSS and reorganized PEDOT:PSS complexes in the highly conductive PEDOT:PSS films. Additives (DMSO, DEG, and PEG 400) were included in PEDOT:PSS aqueous dispersions at large volume fractions. The mixtures were slowly dried under room conditions. During drying, the evaporation of water resulted in an additive-rich solvent mixture from which the reorganized PEDOT:PSS complexes aggregated " into a dense film while free PSS remained in the solution. Upon complete drying, PSS formed a transparent rim film around the conducting PEDOT film. The chemical compositions of the two phases were studied using an infrared microscope. This removal of PSS resulted in more compact packing of PEDOT molecules, as confirmed by X-ray diffraction measurements. X-ray photoelectron spectroscopy and atomic force microscope measurements suggested the enrichment of PEDOT on the film surface after PSS separation. Through a simple drying process in an additive-containing dispersion, the conductivity of PEDOT films increased from 0.1 to 200-400 S/cm. Through this method, we confirmed the existence of two phases in additive-treated and highly conductive PEDOT:PSS films. The proper separation between PSS and PEDOT will be of relevance in designing strategies to process high-performance plastic electrodes.
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| 4. |
- Ouyang, Liangqi, et al.
(författare)
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The contraction of PEDOT films formed on a macromolecular liquid-like surface
- 2018
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Ingår i: Journal of Materials Chemistry C. - : ROYAL SOC CHEMISTRY. - 2050-7526 .- 2050-7534. ; 6:3, s. 654-660
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Tidskriftsartikel (refereegranskat)abstract
- Vapour phase polymerized (VPP) PEDOT obtained using triblock copolymer PEG-PPG-PEG: Fe(III) tosylate polymeric oxidative layers has shown record-high conductivity and unique thermoelectric properties. These properties are related to the molecular weight, morphology and doping of PEDOT. Here we show that in its unwashed condition, the PEDOT chain adopts a neutral benzenoid conformation. The polymer chain converts into the charged quinoid structure after the removal of oxidizers with solvent washing. X-ray diffraction results suggest that the dopant is also incorporated into the packed polymer after the washing process. The changes in the chain structure and doping lead to the characteristic polaron and bipolaron absorption in the 800 and 1200 nm range. We observed a large contraction of the film after washing that is likely due to these changes, along with the removal of excessive polymer: oxidizer trapped in the PEDOT matrix. The contraction of films can be completely suppressed by mechanical clamping. PEDOT films without contraction show both a higher conductivity and higher optical transparency.
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| 5. |
- Tang, Zheng, et al.
(författare)
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Improving Cathodes with a Polymer Interlayer in Reversed Organic Solar Cells
- 2014
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Ingår i: Advanced Energy Materials. - : Wiley-VCH Verlagsgesellschaft. - 1614-6832 .- 1614-6840. ; 4:15
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Tidskriftsartikel (refereegranskat)abstract
- The effects of cathode modification by a conjugated polymer interlayer PFPA1 on the performance of reversed organic solar cells (substrate/cathode/active layer/transparent anode) based on different active material systems and different substrate electrodes are systematically investigated. A reduction of the work function irrespective of the substrate cathode used is observed upon the deposition of the PFPA1 interlayer, which is further related to an improved built-in electric field and open-circuit voltage. The amphiphilic character of the PFPA1 interlayer alters the surface energy of the substrate cathode, leading to the formation of a better active layer morphology aiding efficient exciton dissociation and photocurrent extraction in the modified solar cells. Hence, internal quantum efficiency is found to be significantly higher than that of their unmodified counterparts, while optically, the modified and unmodified solar cells are identical. Moreover, the deep highest occupied molecular orbital (HOMO) of the PFPA1 interlayer improves the selectivity for all investigated substrate cathodes, thus enhancing the fill factor.
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| 6. |
- Tang, Zheng, et al.
(författare)
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Universal modification of poor cathodes into good ones by a polymer interlayer for high performance reversed organic solar cells
- 2014
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- In organic bulk-heterojunction solar cells, energy losses at the active layer/electrode interface are often observed. Modification of these interfaces with organic interlayers optimizes charge carrier injection and extraction and thus improves device performance. In this work, the effects of cathode modification by a conjugated polymer interlayer PFPA1 on the performance of reversed organic solar cells (substrate/cathode/active layer/transparent anode) based on different active material systems and different substrate electrodes are systematically investigated. A reduction of the work function irrespective of the substrate cathode used is observed upon the deposition of the PFPA1 interlayer; further related to an improved built-in electric field and open-circuit voltage. The amphiphilic character of the PFPA1 interlayer alters the surface energy of the substrate cathode, leading to the formation of a better active layer morphology aiding efficient exciton dissociation and photocurrent extraction in the modified solar cells. Hence, internal quantum efficiency is found significantly higher than that of their unmodified counterparts, while optically, the modified and unmodified solar cells are identical. Moreover, the deep HOMO of the PFPA1 interlayer improves the selectivity for all investigated substrate cathodes, thus enhancing the fill factor. We demonstrate a possibility of improving photovoltaic performance of reversed solar cells via a simple and universal interface modification and provide the basic guidelines for development and characterization of interface materials for organic solar cells in general.
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| 7. |
- Wang, Xiangjun, et al.
(författare)
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In-situ Wilhelmy balance surface energy determination of poly(3-hexylthiophene) and poly(3,4-ethylenedioxythiophene) during electrochemical doping-dedoping
- 2006
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 22:22, s. 9287-9294
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Tidskriftsartikel (refereegranskat)abstract
- Changes in the contact angle between conjugated polymers surface poly(3-hexylthiophene) [P3HT] and poly(3,4-ethylenedioxythiophene) (PEDOT) upon electrochemical doping−dedoping in aqueous electrolyte were determined in situ using a Wilhelmy plate tensiometer in an electrochemical cell. The hydrophobic P3HT was less hydrophobic in the oxidized state than in the neutral state; the more hydrophilic PEDOT was less hydrophilic in the oxidized state than when neutral. The tensiometry results were in good agreement with those measured by contact angle goniometry, and further corroborated by the capillary rise upon doping in a fluid cell with two parallel polymer coated plates, another in situ dynamic determination method. The contact angle changes depend on doping potential, electrolyte type, and concentration. We also deconvoluted the surface energy into components of van der Waals and acid−base interactions, using three probe liquids on the polymer surfaces, ex situ the electrochemical cell. The methods and the obtained results are relevant for the science and technology areas of printed electronics and electrochemical devices and for the understanding of surface energy modification by electrochemical doping.
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| 8. |
- Wang, Yuming, et al.
(författare)
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Light-induced degradation of fullerenes in organic solar cells : a case study on TQ1:PC71BM
- 2018
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 6:25, s. 11884-11889
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Tidskriftsartikel (refereegranskat)abstract
- The stability of organic solar cells (OSCs) is critical for practical applications of this emerging technology. Unfortunately, in spite of intensive investigations, the degradation mechanisms in OSCs have not been clearly understood yet. In this report, we employ a range of spectroscopic and transport measurements, coupled with drift-diffusion modelling, to investigate the light-induced degradation mechanisms of fullerene-based OSCs. We find that trap states formed in the fullerene phase under illumination play a critical role in the degradation of the open-circuit voltage (V-OC) in OSCs. Our results indicate that the degradation is intrinsic to the fullerenes in OSCs and that alternative acceptor materials are desired for the development of stable OSCs.
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| 9. |
- Wanzhu, Cai, et al.
(författare)
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Dedoping-induced interfacial instability of poly(ethylene imine)s-treated PEDOT:PSS as a low-work-function electrode
- 2020
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Ingår i: Journal of Materials Chemistry C. - : ROYAL SOC CHEMISTRY. - 2050-7526 .- 2050-7534. ; 8:1, s. 328-336
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Tidskriftsartikel (refereegranskat)abstract
- Transparent organic electrodes printed from high-conductivity PEDOT:PSS have become essential for upscaling all-carbon based, low-cost optoelectronic devices. In the printing process, low-work-function PEDOT:PSS electrodes (cathode) are achieved by coating an ultra-thin, non-conjugated polyelectrolyte that is rich in amine groups, such as poly(ethylene imine) (PEI) or its ethoxylated derivative (PEIE), onto PEDOT:PSS surfaces. Here, we mapped the physical and chemical processes that occur at the interface between thin PEIx (indicating either PEI or PEIE) and PEDOT:PSS during printing. We identify that there is a dedoping effect of PEDOT induced by the PEIx. Using infrared spectroscopy, we found that the amine-rich PEIx can form chemical bonds with the dopant, PSS. At lower PSS concentration, PEIx also shows an electron-transfer effect to the charged PEDOT chain. These interface reactions lock the surface morphology of PEDOT:PSS, preventing the redistribution of PSS, and reduce the work function. Subsequent exposure to oxygen during the device fabrication process, on the other hand, can result in redoping of the low-work-function PEDOT:PSS interface, causing problems for printing reproducible devices under ambient conditions.
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