| 1. |
- Admassie, Shimelis, et al.
(författare)
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A polymer photodiode using vapour-phase polymerized PEDOT as an anode
- 2006
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Ingår i: Solar Energy Materials & Solar Cells. ; 90:2, s. 133-141
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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)]
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| 2. |
- Bjoerstroem, Cecilia M., et al.
(författare)
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Influence of solvents and substrates on the morphology and the performance of low-bandgap polyfluorene: PCBM photovoltaic devices
- 2006
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Ingår i: Proceedings of SPIE-The International Society for Optical Engineering. ; 6192, s. 61921X/1-
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Konferensbidrag (refereegranskat)abstract
- Spin-coated thin films of poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (APFO-3) blended with [6,6]-phenyl-C61-butyric acid Me ester (PCBM) are used as the active material in polymer photovoltaic cells. Such blends are known for their tendency to phase sep. during film formation. Tuning the morphol. of the blend in a controlled way is one possible road towards higher efficiency. We studied the effect of adding chlorobenzene to chloroform-based blend solns. before spin-coating on the conversion efficiency of APFO-3:PCBM photodiodes, and related that to the lateral and vertical morphol. of thin films of the blend. The lateral morphol. is imaged by at. force microscopy (AFM) and the vertical compositional profile is obtained by dynamic secondary ion mass spectrometry (SIMS). The profiles reveal compositional variations consisting of multilayers of alternating polymer-rich and PCBM-rich domains in the blend film spin-coated from chloroform. The vertical compositional variations are caused by surface-directed spinodal waves and are frozen in during the rapid evapn. of a highly volatile solvent. With addn. of the low-vapor pressure solvent chlorobenzene, a more homogeneous vertical compn. is found. The conversion efficiency for solar cells of this blend was found to be optimal for chloroform:chlorobenzene mixts. with a vol.-ratio of 80:1. We have also investigated the role of the substrate on the morphol. We found that blend films spin-coated from chloroform solns. on PEDOT:PSS-coated ITO show a similar compositional structure as the films on silicon, and that changing the substrate from silicon to gold only affects the vertical phase sepn. in a region close to the substrate interface. [on SciFinder (R)]
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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. |
- 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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| 5. |
- Lindgren, Lars Johan, 1977, et al.
(författare)
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Blue light-emitting diodes based on novel polyfluorene copolymers
- 2007
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Ingår i: Journal of Luminescence. ; 122-123, s. 610-613
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Konferensbidrag (refereegranskat)abstract
- This study presents the synthesis and characterization of a series of fluorene-based conjugated copolymers, together with the prepn. and characterization of the corresponding light-emitting devices. The polymers consist of alkoxyphenyl-substituted fluorene units together with different amts. of a hole-transporting triphenylamine-substituted fluorene unit: 0%, 10%, 25% and 50%. All polymers (P0, P1, P2, and P3) show high photoluminescence efficiency (hPL) and light emission (both PL and EL) in the blue spectral region. Electrochem. studies show improved hole injection as the ratio of the triphenylamine-substituted segment is increased. The electroluminescence quantum efficiencies (EQEs) of the devices increase six times going from P0 to P1. Compared with P1, polymers P2 and P3 show lower efficiencies in devices. These findings indicate the presence of an optimal polymer compn., where balance between the charge-carrier mobilities has been reached. [on SciFinder (R)]
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| 6. |
- 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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| 7. |
- 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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| 8. |
- Zhang, Fengling, et al.
(författare)
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Low-bandgap alternating fluorene copolymer/methanofullerene heterojunctions in efficient near-infrared polymer solar cells
- 2006
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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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| 9. |
- Zhang, Fengling, et al.
(författare)
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Theoretical models and experimental results on the temperature dependence of polyfluorene solar cells
- 2006
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Ingår i: Solar Energy Materials & Solar Cells. ; 90:11, s. 1607-1614
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Tidskriftsartikel (refereegranskat)abstract
- The temp. dependence of device parameters of polymer solar cells based on alternating copolyfluorene incorporating dioctyl-fluorene and di-thienyl-benzothiadiazole (APFO-3) mixed with [6,6]-phenyl-C61-butyric acid methylester (PCBM) was modeled theor. by simulation and investigated exptl. under illumination of AM1.5 (100 mW/cm2). Both simulation and exptl. results show photocurrent, fill factor and power conversion efficiency all increase, and the open-circuit voltages monotonically decrease with temp. increase from room temp. (RT) to 120 DegC. These results can be explained by taking into account the temp. dependence of the mobility, and the thermal activation of the injection current from the electrodes. The increase of PCE with temp. is a distinguishing feature of polymer solar cells. [on SciFinder (R)]
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