| 1. |
- 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. ; 156:7-8, s. 614-623
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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)]
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| 2. |
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| 3. |
- Gadisa, Abay, et al.
(författare)
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A new donor-acceptor-donor polyfluorene copolymer with balanced electron and hole mobility
- 2007
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Ingår i: Adv. Funct. Mater. FIELD Full Journal Title:Advanced Functional Materials. ; 17:18, s. 3836-3842
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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)]
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| 4. |
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| 5. |
- Gedefaw, Desta Antenehe, 1971, et al.
(författare)
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Conjugated polymers with polar side chains in bulk heterojunction solar cell devices
- 2014
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Ingår i: Polymer International. - : Wiley. - 1097-0126 .- 0959-8103. ; 63:1, s. 22-30
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Tidskriftsartikel (refereegranskat)abstract
- Two polymers with polar side chains, namely poly[2,7-(9,9-dioctylfluorene)-alt-5,5-(5',8'-di-2-thienyl-(2',3'-bis(3''-(2-(2-methoxyethoxy)ethoxy)phenyl)quinoxaline))] (P1) and poly[2,7-(9,9-bis(2-(2-methoxyethoxy)ethyl)fluorene)-alt-5,5-(5',8'-di-2-thienyl-(2',3'-bis(3''-(2-(2-methoxyethoxy)-ethoxy)phenyl)quinoxaline))] (P2), were synthesized for solar cell application. A series of bulk heterojunction solar cells were systematically fabricated and characterized by varying the electron-acceptor materials, processing solvents and thickness of the active layer. The results show that P1, with a higher molecular weight and good film-forming properties, performed better. The best device showed an open circuit voltage of 0.87 V, a short circuit current of 6.81 mA cm(-2) and a power conversion efficiency of 2.74% with 1:4 polymer:[6,6]-phenyl-C71-butyric acid methyl ester (PCBM[70]) mixture using o-dichlorobenzene (o-DCB) as processing solvent. P2 on the other hand showed a poorer performance with chlorobenzene as processing solvent, but a much improved performance was obtained using o-DCB instead. Thus, an open circuit voltage of 0.80 V, short circuit current of 6.21 mA cm(-2) and an overall power conversion efficiency of 2.22% were recorded for a polymer:PCBM[70] mixing ratio of 1:4. This is presumably due to the improvement of the morphology of the active layer using o-DCB as processing solvent. (c) 2013 Society of Chemical Industry
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| 6. |
- Gedefaw, Desta Antenehe, 1971, et al.
(författare)
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Random polyfluorene co-polymers designed for a better optical absorption coverage of the visible region of the electromagnetic spectrum
- 2014
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Ingår i: Bulletin of the Chemical Society of Ethiopia. - : African Journals Online (AJOL). - 1726-801X .- 1011-3924. ; 28:1, s. 121-130
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Tidskriftsartikel (refereegranskat)abstract
- Two alternating polyfluorenes (APFO15-F8BT and APFO3-F8BT) with full absorption of the visible region of the electromagnetic radiation were designed and synthesized for bulk-heterojunction solar cell devices. The optical and electrochemical properties of the two polymers were studied. The two polymers exhibited strong absorption in the visible region with no significant valley over the visible region extending up to 650 nm. Deep HOMO and ideally situated LUMO energy levels were the characteristics of the two polymers as revealed from the square wave voltammogram study: desired properties for extracting high open circuit voltage and for a facile charge transfer to the acceptor component in devices to take place, respectively. Photovoltaic devices were fabricated by blending the two polymers with PCBM[70] and up to similar to 2% power conversion efficiency were obtained.
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| 7. |
- Inganaes, Olle, et al.
(författare)
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Alternating fluorene copolymer-fullerene blend solar cells
- 2005
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Ingår i: Optical Science and Engineering. ; 99, s. 387-402
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Tidskriftsartikel (refereegranskat)abstract
- We present a new class of alternating fluorene copolymers, which can be combined with a fullerene acceptor, to make polymer blends suitable for photovoltaic energy conversion. By choice of comonomers in the polymer, it is possible to engineer the optical absorption spectrum and to cover the wavelength range down to 900 nm. The transport properties of the polymers investigated so far are competitive with other polymers used in polymer solar cells and the mixing of polymers with acceptors in the form of fullerenes is extensive. These polymers are therefore of interest in the future developments of high-performance polymer solar cells. [on SciFinder (R)]
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| 8. |
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| 9. |
- Lindgren, Lars Johan, 1977, et al.
(författare)
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Synthesis, Characterization, and Devices of a Series of Alternating Copolymers for Solar Cells
- 2009
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Ingår i: CHEMISTRY OF MATERIALS. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 21:15, s. 3491-3502
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Tidskriftsartikel (refereegranskat)abstract
- In this study we report the synthesis, characterization. and photovoltaic properties of a series of six Conjugated polymers based on donor-acceptor-donor (DAD) structure. The polymers are obtained via Suzuki polymerization of different alkoxy-substituted DAD monomers together with a substituted fluorene or phenylene monomer. Application of polymers as light-harvesting and electron-donating materials in solar cells, in conjunction with both [60]PCBM and [70]PCBM as acceptors, show power-conversion efficiencies (PCEs) up to 2.9%, values obtained without extensive optimization work. Furthermore, atomic force microscopy and field-effect transistor (FET) mobility measurements of acceptor-polymer mixtures show that differences in substitution on the polymers affect morphology, mobility, and device performance. Within the series of polymers, all showing similar optical absorption and redox behavior, substituents play an important role in phase separation on a micrometer scale, which in turn has a large impact on device performance. The phase-separation behavior is clearly seen in [70]PCBM devices where the best-performing devices are obtained using the polymers with short alkoxy groups or no substituents together with a high speed of spin coating during device preparation.
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| 10. |
- Ma, Zaifei, et al.
(författare)
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A Facile Method to Enhance Photovoltaic Performance of Benzodithiophene-Isoindigo Polymers by Inserting Bithiophene Spacer
- 2014
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Ingår i: Advanced Energy Materials. - : Wiley. - 1614-6840 .- 1614-6832. ; 4:6, s. Art. no. 1301455-
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Tidskriftsartikel (refereegranskat)abstract
- This study describes the synthesis and characterization of four polymers based on benzo[1,2-b:4,5-b']dithiophene (BDT) and isoindigo with zero, one, two, and three thiophene spacer groups. Results have demonstrated that the use of bithiophene as a spacer unit improves the geometry of the polymer chain, making it planar, and hence, potentially enhanced π- π stacking occurs. Due to favorable interaction of the polymer chains, enhanced absorption coefficient, and optimal morphology, PBDT-BTI, which possesses bithiophene as a spacer, revealed high current and fill factor leading to a power conversion efficiency of 7.3% in devices, making this polymer the best performing isoindigo-based material in polymer solar cells (PSCs). Also, PBDT-BTI could still maintain efficiency of over 6% with the active layer thickness of 270 nm, making it a potential candidate for a material in printed PSCs. These results demonstrate that the use of thiophene spacers in D-A polymers could be an important design strategy to produce high-performance PSCs.
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| 11. |
- Mammo, Wendimagegn, 1954, et al.
(författare)
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New low band gap alternating polyfluorene copolymer-based photovoltaic cells
- 2007
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Ingår i: Sol. Energy Mater. Sol. Cells FIELD Full Journal Title:Solar Energy Materials & Solar Cells. ; 91:11, s. 1010-1018
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Tidskriftsartikel (refereegranskat)abstract
- New low band gap alternating polyfluorene copolymers were synthesized for use in plastic solar cells and their optical, electrochem., and photovoltaic characteristics 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 HOMO-LUMO values were estd. from electrochem. studies. By varying the donor and acceptor strength and position of the solubilizing substituents, similar HOMO values were obtained. These values were also found to correlate well with the open circuit voltage (VOC) values detd. from photovoltaic data of the polymers blended with the acceptor PCBM. Despite similar HOMO values, the absorption spectra of the polymers differ significantly. This prompted the prepn. of photovoltaic devices consisting of blends of two polymers with complementary absorptions in combination with PCBM to harvest more photons in the polymer solar cells. [on SciFinder (R)]
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| 12. |
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| 13. |
- Perzon, Erik Per, 1977, et al.
(författare)
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Design, Synthesis and Properties of Low Band Gap Polyfluorenes for Photovoltaic Devices
- 2005
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Ingår i: Synthetic Metals. ; 154:1-3, s. 53-56
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Konferensbidrag (refereegranskat)abstract
- Two alternating polyfluorene-polythiophene copolymers contg. different low band gap 4,7-di-2-thienyl-2,1,3-benzothiadiazole-5,6-diamine segments were designed and synthesized for use in optoelectronic devices. The low band gap segments consist of electron donating and accepting moieties which induce a partial charge transfer in the polymer backbone and thereby, a lower band gap. The obtained polyfluorenes, APFO-Green1 and APFO-Green2, were studied by measuring optical absorption and emission at extended wavelengths. Blends of the polyfluorenes with fullerene derivs. exhibit unprecedented photovoltaic response at long wavelengths. [on SciFinder (R)]
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| 14. |
- Tehrani, Payman, 1977-, et al.
(författare)
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Evaluation of active materials designed for use in printable electrochromic polymer displays
- 2006
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 515:4, s. 2485-2492
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Tidskriftsartikel (refereegranskat)abstract
- In a step towards roll-to-roll production of polymer-based electrochromic displays on flexible substrates, nine thiophene-based polymers and copolymers designed to increase the contrast of displays based on poly(3,4-ethylenedioxythiophene)/poly(styrene-sulfonic acid) have been synthesized and evaluated with respect to their absorbance (contrast), switch speed, and ability to switch reversibly in a water-based electrolyte. The results of the evaluation, including cyclic voltammetry and optically visible absorption, provide a basis for understanding what an aqueous electrolyte electrochromic display requires in terms of oxidation potential and material stability, and the effect of chemical structure on the reversibility and speed of switching. © 2006 Elsevier B.V. All rights reserved.
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| 15. |
- Waketola, Alemayehu G., et al.
(författare)
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Embedding plasmonic gold nanoparticles in a ZnO layer enhanced the performance of inverted organic solar cells based on an indacenodithieno[3,2-b]thiophene-alt-5,5'-di(thiophen-2-yl)-2,2'-bithiazole-based push-pull polymer
- 2023
-
Ingår i: RSC Advances. - 2046-2069. ; 13:24, s. 16175-16184
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Tidskriftsartikel (refereegranskat)abstract
- Recently, plasmonic nanoparticles (NPs) have attracted considerable attention as good candidates for enhancing the power conversion efficiency (PCE) of organic solar cells (OSCs) owing to their localized surface plasmon resonance (LSPR). In this study, the effect of embedding colloidal gold nanoparticles (cAu NPs) in the ZnO electron transport layer (ETL) on the PCEs of wide band gap polymer-based inverted OSCs was investigated. The active layer was composed of a bulk heterojunction of conjugated polymer based on indacenodithieno[3,2-b]thiophene and 5,5'-di(thiophen-2-yl)-2,2'-bithiazole PIDTT-DTBTz as a donor and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) as an acceptor. The PCE of the reference device was improved by 22% when 10 wt% cAu NPs were embedded in the ZnO ETL. The short circuit current density (J(SC)) and fill factor (FF) were the main photovoltaic parameters contributing to the PCE enhancement. An improved absorption in the active layer due to the LSPR of cAu NPs as well as efficient exciton dissociation and charge collection were found to be the reasons for the enhanced J(SC) while the increase in FF was mainly due to the suppressed traps and improved conductivity of the ZnO layer by the NPs.
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| 16. |
- Wang, Ergang, 1981, et al.
(författare)
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Small Band Gap Polymers Synthesized via a Modified Nitration of 4,7-Dibromo-2,1,3-benzothiadiazole
- 2010
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Ingår i: Organic Letters. - : American Chemical Society (ACS). - 1523-7052 .- 1523-7060. ; 12:20, s. 4470-4473
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Tidskriftsartikel (refereegranskat)abstract
- The nitration of 4,7-dibromo-2,1,3-benzothiadiazole was modified by using CF3SO3H and HNO3 as the nitrating agent, and the related yield was improved greatly. On the basis of this improvement, two new small band gap polymers, P1TPQ and P3TPQ, were developed. Bulk heterojunction solar cells based on P3TPO and [6,6]-phenyl-C-71-butyric acid methyl ester exhibit interesting results with a power conversion efficiency of 21% and photoresponse up to 1.1 mu m
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| 17. |
- Wang, Xiangjun, et al.
(författare)
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Polymer solar cells with low-bandgap polymers blended with C70-derivative give photocurrent at 1 μm
- 2006
-
Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090. ; 511-512, s. 576-580
-
Tidskriftsartikel (refereegranskat)abstract
- A new series of low-bandgap alternating polyfluorenes with different donor–acceptor–donor moieties have been synthesized. Electrochemical and optical absorption measurement show that onset bandgaps of these polymers range from 1.2 to 1.5 eV. These polymers, blended with a C70-derivative as acceptor, are used for solar cell fabrication. Devices show promising photovoltaic properties, and the spectral response of photocurrent covers all visible and near-infrared wavelength regions with its onset extended to 1 μm. The best data gives a photocurrent density of 3.4 mA/cm2, open circuit voltage of 0.58 V and power conversion efficiency of 0.7% under illumination of AM1.5 (1000 W/m2) from a solar simulator.
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| 18. |
- Zhang, Fengling, et al.
(författare)
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Low-bandgap alternating fluorene copolymer/methanofullerene heterojunctions in efficient near-infrared polymer solar cells
- 2006
-
Ingår i: Advanced Materials (Weinheim, Germany). ; 18:16, s. 2169-2173
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Tidskriftsartikel (refereegranskat)abstract
- Efficient near-IR polymer solar cells based on the low-bandgap alternating fluorene copolymer APFO-Green 5 exhibit a photoresponse up to 800 nm. The copolymer performs well in combination with the common electron acceptor [6,6]-phenyl-C61-butyric acid Me ester (PCBM), reaching a power-conversion efficiency of 2.2% with a lower PCBM content in the active layer than previous devices based on low-bandgap polymers. [on SciFinder (R)]
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| 19. |
- Zhang, Fengling, 1960-, et al.
(författare)
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Polymer solar cells based on a low-bandgap fluorene copolymer and a fullerene derivative with photocurrent extended to 850 nm
- 2005
-
Ingår i: Advanced Functional Materials. - : Wiley. - 1616-3028 .- 1616-301X. ; 15:5, s. 745-750
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Tidskriftsartikel (refereegranskat)abstract
- Polymer solar cells were fabricated from a low band-gap alternating polyfluorene copolymer, APFO-Green2, combined with [6,6]-phenyl-C61-butyric acid Me ester (PCBM), from org. solns. External quantum efficiencies of the solar cells show an onset at 850 nm and a peak of >10% located at 650 nm, which corresponds to the extended absorption spectrum of the polymer. A photocurrent of 3.0 mA/cm2, photovoltage of 0.78 V, and power conversion efficiency of 0.9% were obtained with solar cells based on this new low-bandgap polymer under an illumination of AM 1.5 (1000 W/m2) from a solar simulator. [on SciFinder (R)]
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| 20. |
- Zhou, Yi, et al.
(författare)
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Black Polymers in Bulk-Heterojunction Solar Cells
- 2010
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Ingår i: IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS. - : Institute of Electrical and Electronics Engineers (IEEE). - 1077-260X .- 1558-4542. ; 16:6, s. 1565-1572
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Tidskriftsartikel (refereegranskat)abstract
- The active materials in polymer solar cells have a decisive role on the performance of the cells. Polymers with extended absorption, i.e., black polymers with absorption covering the whole visible region are desired in order to capture the important parts of the solar irradiation. Different ways of achieving black active materials are discussed and two new alternating polyfluorene (APFO) copolymers with broad absorption, APFO-Black 1 and APFO-Black 2, using two different design strategies are described. The UV-Vis absorption spectra of the polymers extend to approximately 850 nm, and the polymers were used as donors and [6,6]-phenyl-C-61-butyric acid methyl ester (PCBM)[60] or PCBM[70] as acceptors in solar cell devices in various mixing ratios. The best combinations yielded an overall power conversion efficiency of 1.2% for APFO-Black 1 and 1.5% for APFO-Black 2.
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