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| 2. |
- Admassie, Shimelis, et al.
(författare)
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A renewable biopolymer cathode with multivalent metal ions for enhanced charge storage
- 2014
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Ingår i: JOURNAL OF MATERIALS CHEMISTRY A. - : Royal Society of Chemistry. - 2050-7488. ; 2:6, s. 1974-1979
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Tidskriftsartikel (refereegranskat)abstract
- A ternary composite supercapacitor electrode consisting of phosphomolybdic acid (HMA), a renewable biopolymer, lignin, and polypyrrole was synthesized by a simple one-step simultaneous electrochemical deposition and characterized by electrochemical methods. It was found that the addition of HMA increased the specific capacitance of the polypyrrole-lignin composite from 477 to 682 F g(-1) ( at a discharge current of 1 A g(-1)) and also significantly improved the charge storage capacity from 6(to 128 mA h g(-1).
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| 3. |
- Admassie, Shimelis, et al.
(författare)
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Biopolymer hybrid electrodes for scalable electricity storage
- 2016
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Ingår i: Materials Horizons. - : ROYAL SOC CHEMISTRY. - 2051-6347 .- 2051-6355. ; 3:3, s. 174-185
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Forskningsöversikt (refereegranskat)abstract
- Powering the future, while maintaining a cleaner environment and a strong socioeconomic growth, is going to be one of the biggest challenges faced by mankind in the 21st century. The first step in overcoming the challenge for a sustainable future is to use energy more efficiently so that the demand for fossil fuels can be reduced drastically. The second step is a transition from the use of fossil fuels to renewable energy sources. In this sense, organic electrode materials are becoming increasingly attractive compared to inorganic electrode materials which have reached a plateau regarding performance and have severe drawbacks in terms of cost, safety and environmental friendliness. Using organic composites based on conducting polymers, such as polypyrrole, and abundant, cheap and naturally occurring biopolymers rich in quinones, such as lignin, has recently emerged as an interesting alternative. These materials, which exhibit electronic and ionic conductivity, provide challenging opportunities in the development of new charge storage materials. This review presents an overview of recent developments in organic biopolymer composite electrodes as renewable electroactive materials towards sustainable, cheap and scalable energy storage devices.
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| 4. |
- Admassie, Shimelis, et al.
(författare)
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Electrochemical and optical studies of the band gaps of alternating polyfluorene copolymers
- 2006
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Ingår i: Synthetic metals. - : Elsevier BV. - 0379-6779 .- 1879-3290. ; 156:7-8, s. 614-623
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Tidskriftsartikel (refereegranskat)abstract
- The electrochemical and optical properties of a series of alternating polyfluorene copolymers with low band gaps were determined. These polymers incorporated fluorene units alternating with groups including electron-withdrawing (A) and electron-donating (D) groups in donor-acceptor-donor (DAD) sequence to achieve the lowering of band gaps. The polymers were solvent-casted on platinum disk electrode and the band gaps were estimated from cyclic voltammetry (CV). These values were compared with values obtained from optical absorption measurements. Although the electrochemically determined band gaps were found to be slightly higher than the optical band gap in most cases, values are well correlated. The values of the band gaps determined range from 2.1 to 1.3 eV. © 2006 Elsevier B.V. All rights reserved.
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| 5. |
- Gadisa, Abay, et al.
(författare)
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Stoichiometry dependence of charge transport in polymer/methanofullerene and polymer/C70 derivative based solar cells
- 2006
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Ingår i: Organic electronics. - : Elsevier BV. - 1566-1199. ; 7:4, s. 195-204
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Tidskriftsartikel (refereegranskat)abstract
- Charge transport in a near infrared absorbing polyfluorene copolymer (APFO-Green1) and its blends with methanofullerene [6,6]-phenyl C61-butyric acid methyl ester (PCBM), and 3′-(3,5-bis-trifluoromethylphenyl)-1′-(4-nitrophenyl)pyrazolino[70]fullerene (BTPF70) is reported. PCBM and BTPF70 are electron acceptor and transporting molecules in polymer based solar cells. The BTPF70 has emerged as a new electron acceptor molecule that provides adequate exciton dissociation when blended with the low band gap polyfluorene copolymer APFO-Green1. Electron transport in both net PCBM and BTPF70 films are subjected to positional and energetic disorder, with the degree of disorder being more pronounced in BTPF70. On the other hand, mixing PCBM with conjugated polymers usually leads to increased hole mobility. We have investigated and compared the acceptor concentration dependence of charge transport in APFO-Green1/PCBM and APFO-Green1/BTPF70 blend films. For better understanding of the charge transport in the heterojunction films, the field and temperature dependence of hole transport in pure APFO-Green1 films has also been studied. It is observed that the behavior of hole mobility in the blend layer is sensitive to the acceptor type. For APFO-Green1/PCBM hole only devices, the hole mobility attains a local maximum at 67 wt.% of PCBM, while on the contrary mixing any amount of BTPF70 with APFO-Green1 results into degradation of hole transport. Electron transport in both blends, however, increases monotonically as a function of acceptor loading.
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| 6. |
- Gadisa, Abay, et al.
(författare)
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Transparent polymer cathode for organic photovoltaic devices
- 2006
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Ingår i: Synthetic metals. - : Elsevier BV. - 0379-6779 .- 1879-3290. ; 156:16-17, s. 1102-1107
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a prototype solar cell with a transparent polymer cathode, and indium-tin-oxide (ITO)/poly (3, 4-ethylene dioxythiophene)-poly (styrene sulphonate) (PEDOT:PSS) anode. As an active layer, thin film of a bulk heterojunction of polyfluorene copolymer poly[2,7-(9,9-dioctyl-fluorene)-alt-5,5-(4′,7′-di-2thienyl-2′,1′3′-benzothiadiazole)] (APFO-3) and an electron acceptor molecule [6] and [6]-phenyl-C61-butyric acid methyl ester (PCBM) (1:4 wt.) was sandwiched between the two transparent polymer electrodes. The cathode is another form of PEDOT formed by vapor phase polymerised PEDOT (VPP PEDOT) of conductivity 102–103 S/cm. The cathode is supported on an elastomeric substrate, and forms a conformal contact to the APFO-3/PCBM blend. Transparent solar cells are useful for building multilayer and tandem solar cells.
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| 7. |
- Inganäs, Olle, et al.
(författare)
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25th Anniversary Article: Organic Photovoltaic Modules and Biopolymer Supercapacitors for Supply of Renewable Electricity: A Perspective from Africa
- 2014
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Ingår i: Advanced Materials. - : Wiley-VCH Verlag. - 0935-9648 .- 1521-4095. ; 26:6, s. 830-847
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Forskningsöversikt (refereegranskat)abstract
- The role of materials in civilization is well demonstrated over the centuries and millennia, as materials have come to serve as the classifier of stages of civilization. With the advent of materials science, this relation has become even more pronounced. The pivotal role of advanced materials in industrial economies has not yet been matched by the influence of advanced materials during the transition from agricultural to modern societies. The role of advanced materials in poverty eradication can be very large, in particular if new trajectories of social and economic development become possible. This is the topic of this essay, different in format from the traditional scientific review, as we try to encompass not only two infant technologies of solar energy conversion and storage by means of organic materials, but also the social conditions for introduction of the technologies. The development of organic-based photovoltaic energy conversion has been rapid, and promises to deliver new alternatives to well-established silicon photovoltaics. Our recent development of organic biopolymer composite electrodes opens avenues towards the use of renewable materials in the construction of wooden batteries or supercapacitors for charge storage. Combining these new elements may give different conditions for introduction of energy technology in areas now lacking electrical grids, but having sufficient solar energy inputs. These areas are found close to the equator, and include some of the poorest regions on earth.
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| 8. |
- Patil, Nagaraj, et al.
(författare)
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Bioinspired Redox-Active Catechol-Bearing Polymers as Ultrarobust Organic Cathodes for Lithium Storage
- 2017
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Ingår i: Advanced Materials. - : WILEY-V C H VERLAG GMBH. - 0935-9648 .- 1521-4095. ; 29:40
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Tidskriftsartikel (refereegranskat)abstract
- Redox-active catechols are bioinspired precursors for ortho-quinones that are characterized by higher discharge potentials than para-quinones, the latter being extensively used as organic cathode materials for lithium ion batteries (LIBs). Here, this study demonstrates that the rational molecular design of copolymers bearing catechol-and Li+ ion-conducting anionic pendants endow redox-active polymers (RAPs) with ultrarobust electrochemical energy storage features when combined to carbon nanotubes as a flexible, binder-, and metal current collector-free buckypaper electrode. The importance of the structure and functionality of the RAPs on the battery performances in LIBs is discussed. The structure-optimized RAPs can store high-capacities of 360 mA h g(-1) at 5C and 320 mA h g(-1) at 30C in LIBs. The high ion and electron mobilities within the buckypaper also enable to register 96 mA h g(-1) (24% capacity retention) at an extreme C-rate of 600C (6 s for total discharge). Moreover, excellent cyclability is noted with a capacity retention of 98% over 3400 cycles at 30C. The high capacity, superior active-material utilization, ultralong cyclability, and excellent rate performances of RAPs-based electrode clearly rival most of the state-of-the-art Li+ ion organic cathodes, and opens up new horizons for large-scalable fabrication of electrode materials for ultrarobust Li storage.
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| 9. |
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| 10. |
- Wang, Xiangjun, et al.
(författare)
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Enhanced photocurrent spectral response in low-bandgap polyfluorene and C70-Derivative-Based Solar Cells
- 2005
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Ingår i: Advanced Functional Materials. - : Wiley. - 1616-301X .- 1616-3028. ; 15:10, s. 1665-1670
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Tidskriftsartikel (refereegranskat)abstract
- Plastic solar cells have been fabricated using a low-bandgap alternating copolymer of fluorene and a donor-acceptor-donor moiety (APFO-Green1), blended with 3-(3,5-bis-trifluoromethylphenyl)-1-(4-nitrophenyl)pyrazolino[70]fullerene (BTPF70) as electron acceptor. The polymer shows optical absorption in two wavelength ranges, < 500 nm and 600 < < 1000 nm. The BTPF70 absorbs light at < 700 nm. A broad photocurrent spectral response in the wavelength range 300 < < 1000 nm is obtained in solar cells. A photocurrent density of 3.4 mA cm-2, open-circuit voltage of 0.58 V, and power-conversion efficiency of 0.7 % are achieved under illumination of AM1.5 (1000 W m-2) from a solar simulator. Synthesis of BTPF70 is presented. Photoluminescence quenching and electrochemical studies are used to discuss photoinduced charge transfer.
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