| 1. |
|
|
| 2. |
- Admassie, Shimelis, et al.
(författare)
-
A polymer photodiode using vapour-phase polymerized PEDOT as an anode
- 2006
-
Ingår i: Solar Energy Materials & Solar Cells. ; 90:2, s. 133-141
-
Tidskriftsartikel (refereegranskat)abstract
- We report the photovoltaic properties of devices made using a highly conducting polymer electrode, from vapor-phase polymd. poly (3,4-ethylenedioxy) thiophene (VPP PEDOT) on glass substrate as an anode and a polyfluorene copolymer poly[2,7-(9,9-dioctyl-fluorene)-alt-5,5-(4',7'-di-2thienyl-2',1'3'-benzothiadiazole)] (APFO-3) mixed with [6,6]-phenyl-C61-butyric acid methylester (PCBM) in the ratio of 1:4 as the active layer. The device performance was compared with that of devices made with PEDOT-PSS on glass substrates. The surfaces of VPP PEDOT were imaged using at. force microscopy (AFM). [on SciFinder (R)]
|
|
| 3. |
- Admassie, Shimelis, et al.
(författare)
-
A renewable biopolymer cathode with multivalent metal ions for enhanced charge storage
- 2014
-
Ingår i: JOURNAL OF MATERIALS CHEMISTRY A. - : Royal Society of Chemistry. - 2050-7488. ; 2:6, s. 1974-1979
-
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).
|
|
| 4. |
- Admassie, Shimelis, et al.
(författare)
-
Biopolymer hybrid electrodes for scalable electricity storage
- 2016
-
Ingår i: Materials Horizons. - : ROYAL SOC CHEMISTRY. - 2051-6347 .- 2051-6355. ; 3:3, s. 174-185
-
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.
|
|
| 5. |
- Admassie, Shimelis, et al.
(författare)
-
Charge storage properties of biopolymer electrodes with (sub)tropical lignins
- 2014
-
Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 16:45, s. 24681-24684
-
Tidskriftsartikel (refereegranskat)abstract
- The electrochemical and charge storage properties of different lignins inside biopolymer electrodes were studied and correlated with the chemical variations of the lignins as indicated from the nuclear magnetic resonance (NMR) spectroscopic data. The varying fractions of monolignols were found to correlate with charge storage properties. It was found that as the sinapyl to guaiacyl (S/G) ratio increased both the specific capacitance and charge capacity increased considerably. This indicates that quinones generated on S-units can contribute more to charge storage in the biopolymer electrodes.
|
|
| 6. |
- Admassie, Shimelis, et al.
(författare)
-
Electrochemical and optical studies of the band gaps of alternating polyfluorene copolymers
- 2006
-
Ingår i: Synthetic metals. - : Elsevier BV. - 0379-6779 .- 1879-3290. ; 156:7-8, s. 614-623
-
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.
|
|
| 7. |
- Admassie, Shimelis, et al.
(författare)
-
Electrochemical and optical studies of the band gaps of alternating polyfluorene copolymers
- 2006
-
Ingår i: Synthetic Metals. ; 156:7-8, s. 614-623
-
Tidskriftsartikel (refereegranskat)abstract
- The electrochem. and optical properties of alternating polyfluorene copolymers with low band gaps were detd. 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 Pt disk electrode and the band gaps were estd. from cyclic voltammetry (CV). These values were compared with values obtained from optical absorption measurements. Although the electrochem. detd. band gaps are slightly higher than the optical band gap in most cases, values are well correlated. The values of the band gaps detd. range from 2.1 to 1.3 eV. [on SciFinder (R)]
|
|
| 8. |
- Admassie, Shimelis, et al.
(författare)
-
Synthesis, optical and electrochemical characterization of anthrancene and benzothiadiazole-containing polyfluorene copolymers
- 2006
-
Ingår i: Bulletin of the Chemical Society of Ethiopia. - 1011-3924 .- 1726-801X. ; 20:2, s. 309-317
-
Tidskriftsartikel (refereegranskat)abstract
- New solution-processable, anthrancene- and benzothiadiazole-containing polyfluorene copolymers (P1-P3) have been synthesized and characterized. The preparation and characterization of the corresponding blue light-emitting devices are also reported. Polymers P2 and P3 show high photoluminescence efficiency while polymer P2 does not show any significant light emission up to 8.0 V. The results show the need for balance of electron and hole transport in polymer light emitting diodes.
|
|
| 9. |
- Gadisa, Abay, et al.
(författare)
-
A new donor-acceptor-donor polyfluorene copolymer with balanced electron and hole mobility
- 2007
-
Ingår i: Adv. Funct. Mater. FIELD Full Journal Title:Advanced Functional Materials. ; 17:18, s. 3836-3842
-
Tidskriftsartikel (refereegranskat)abstract
- A new alternating polyfluorene copolymer poly[2,7-(9,9-dioctylfluoren)-alt-5,5-(5',8'-di-2-thienyl-(2',3'-bis-(3''-octyloxyphenyl)-quinoxaline))] (APFO-15), which has electron donor-acceptor-donor units in between the fluorene units, is synthesized and characterized. This polymer has a strong absorption and emission in the visible range of the solar spectrum. Its electroluminescence and photolumin escence emissions extend from about 560 to 900 nm. Moreover, solar cells with efficiencies in excess of 3.5 % have been realized from blends of APFO-15 and an electron acceptor mol., a mathanofullerene [6,6]-phenyl-C61-butyric acid Me ester (PCBM). It has also been obsd. that electron and hole transport is balanced both in the pure polymer phase and in polymer/PCBM bulk heterojunction films, which makes this material quite attractive for applications in opto-electronic devices. [on SciFinder (R)]
|
|
| 10. |
- Gadisa, Abay, et al.
(författare)
-
Stoichiometry dependence of charge transport in polymer/methanofullerene and polymer/C70 derivative based solar cells
- 2006
-
Ingår i: Organic electronics. - : Elsevier BV. - 1566-1199. ; 7:4, s. 195-204
-
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.
|
|
