| 1. |
- Andersson, Mattias, et al.
(author)
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Intrinsic and extrinsic influences on the temperature dependence of mobility in conjugated polymers
- 2008
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In: Organic electronics. - : Elsevier. - 1566-1199 .- 1878-5530. ; 9:5, s. 569-574
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Journal article (peer-reviewed)abstract
- The temperature dependence of charge carrier mobility in conjugated polymers and their blends with fullerenes is investigated with different electrical methods, through field effect transistor (FET), space charge limited current (SCLC) and charge extraction (CELIV) measurements. Simple models, such as the Gaussian disorder model (GDM), are shown to accurately predict the temperature behavior, and a good correlation between the different measurement methods is obtained. Inconsistent charge carrier concentrations in the modeling are explained through intrinsic non-equilibrium effects, and are responsible for the limited applicability of existing numerical models. A severe extrinsic influence from water in FETs with a hydrophilic insulator interface is also demonstrated. The presence of water leads to a significant overestimate of the disorder in the materials from measurements close to room temperature and erratic behavior in the 150-350 K range. To circumvent this problem it is shown to be necessary to measure under ultra high vacuum (UHV) conditions. © 2008 Elsevier B.V. All rights reserved.
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| 2. |
- Barrau, Sophie, et al.
(author)
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Nanomorphology of Bulk Heterojunction Organic Solar Cells in 2D and 3D Correlated to Photovoltaic Performance
- 2009
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In: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 42:13, s. 4646-4650
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Journal article (peer-reviewed)abstract
- Control of the nanoscale morphology of the donor-acceptor material blends inorganic solar Cells is critical for optimizing the photovoltaic performances. The influence of intrinsic (acceptor materials) and extrinsic (donor:acceptor weight ratio, substrate, solvent) parameters was investigated, by atomic force microscopy (AFM) and electron tomography (ET), on the nanoscale phase separation of blends of a low-band-gap alternating polyfluorene copolymers (APFO-Green9) with [6,6]-phenyl-C-71-butyric acid methyl ester ([70]PCBM). The photovoltaic performances display an optimal efficiency for the device elaborated with a 1:3 APFO-Green polymer:[70][PCBM weight ratio and spin-coated from chloroform solution. The associated active layer morphology presents small phase-separated domains which is a good balance between as a large interfacial donor-acceptor area and Continuous paths of the donor and acceptor phases to the electrodes.
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| 3. |
- Bjorstrom, C. M., et al.
(author)
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Vertical phase separation in spin-coated films of a low bandgap polyfluorene/PCBM blend - Effects of specific substrate interaction
- 2007
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In: Applied Surface Science. - Amsterdam : Elsevier BV. - 0169-4332 .- 1873-5584. ; 253:8, s. 3906-3912
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Journal article (peer-reviewed)abstract
- We report on the effect of the substrate on the vertical phase separation in spin-coated thin films of poly [(9,9-dioctylfluorenyl-2,7-diyl)-co-5,5-4',7'-di-2-thienyl-2',1',3'-benz othiadiazole] (APFO-3) blended with [6,6]-phenyl-C-61-butyric acid methyl ester (PCBM). Compositional depth profiles of the films are measured by dynamic secondary ion mass spectrometry (SIMS). We found that changing the substrate from silicon to gold affects the composition profile near the substrate interface. This is caused by a specific interaction between the polymer (APFO-3) and the gold surface, as confirmed by X-ray photoelectron spectroscopy (XPS). The composition profile in the area away from the substrate interface, as well as the enrichment of the free surface with APFO-3, remain however unaffected by the choice of substrate. The vertical composition was also analysed for APFO-3:PCBM films spin-coated on indium tin oxide (ITO) coated with a thin layer of (3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS). (c) 2006 Elsevier B.V. All rights reserved.
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| 4. |
- Chen, Miaoxiang, 1962-, et al.
(author)
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High carrier mobility in low band gap polymer-based field-effect transistors
- 2005
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In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 87:25, s. 252105-1-252105-3
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Journal article (peer-reviewed)abstract
- A conjugated polymer with a low band gap of 1.21 eV, i.e., absorbing infrared light, is demonstrated as active material in field-effect transistors (FETs). The material consists of alternating fluorene units and low band gap segments with electron donor-acceptor-donor units composed of two electron-donating thiophene rings attached on both sides of a thiadiazolo-quinoxaline electron-acceptor group. The polymer is solution-processable and air-stable; the resulting FETs exhibit typical p-channel characteristics and field-effect mobility of 0.03 cm2 V−1 s−1.
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| 5. |
- Gadisa, Abay, et al.
(author)
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A new donor-acceptor-donor polyfluorene copolymer with balanced electron and hole mobility
- 2007
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In: Adv. Funct. Mater. FIELD Full Journal Title:Advanced Functional Materials. ; 17:18, s. 3836-3842
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Journal article (peer-reviewed)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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| 6. |
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| 7. |
- Lindgren, Lars Johan, 1977, et al.
(author)
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Synthesis, Characterization, and Devices of a Series of Alternating Copolymers for Solar Cells
- 2009
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In: CHEMISTRY OF MATERIALS. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 21:15, s. 3491-3502
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Journal article (peer-reviewed)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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| 8. |
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| 9. |
- Svanstrom, C. M. B., et al.
(author)
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Device Performance of APFO-3/PCBM Solar Cells with Controlled Morphology
- 2009
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In: Advanced Materials. - Weinheim : Wiley. - 0935-9648 .- 1521-4095. ; 21:43, s. 4398-
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Journal article (peer-reviewed)abstract
- Polymer/fullerene solar cells with three different device structures: A) diffuse bilayer, B) spontaneously formed multilayer and C) vertically homogeneous thin films, are fabricated. The photocurrent/voltage performance is compared and it is found that the self-stratified structure (B) yields the highest energy conversion efficiency.
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| 10. |
- Zhang, Fengling, et al.
(author)
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Low-bandgap alternating fluorene copolymer/methanofullerene heterojunctions in efficient near-infrared polymer solar cells
- 2006
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In: Advanced Materials (Weinheim, Germany). ; 18:16, s. 2169-2173
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Journal article (peer-reviewed)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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