| 1. |
- Aasmundtveit, K.E., et al.
(författare)
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Structural anisotropy of poly(alkylthiophene) films
- 2000
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Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 33:8, s. 3120-3127
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Tidskriftsartikel (refereegranskat)abstract
- The structural anisotropy of various poly(alkylthiophene) films have been studied by X-ray diffraction, using both conventional methods and synchrotron radiation at grazing incidence. Solution-cast films orient with the side chains preferably normal to the film surface, whereas spin-cast films of nonstereoregular material orient with both the main and the side chains in the film plane. For thick (10-50 µm) solution-cast films, the degree of orientation depends strongly on the solvent used for casting, and on the stereoregularity of the polymer, films of stereoregular materials being more oriented than those of nonregular materials. The most oriented nonregular films are those cast from mixtures of chloroform and tetrahydrofuran. Thin (50-500 nm) solution-cast films are more oriented than the thicker ones, and the effects of different stereoregularity or different casting solvents are small. For spin-cast films, the degree of orientation is independent of substrate and solvent. Spin-cast films of stereoregular material have two different phases: One with the side chains normal to the substrate, and another where they are parallel to the substrate. The diffraction peaks of spin-cast poly(octylthiophene) narrow considerably upon heating.
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| 2. |
- Alkadir Abdulahi, Birhan, 1985, et al.
(författare)
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Open-Circuit Voltage Modulations on All-Polymer Solar Cells by Side Chain Engineering on 4,8-Di(thiophen-2-yl)benzo[1,2- b:4,5- b′]dithiophene-Based Donor Polymers
- 2018
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Ingår i: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 1:6, s. 2918-2926
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Tidskriftsartikel (refereegranskat)abstract
- In recent years, all-polymer solar cells (all-PSCs), incorporating active layers based on blends of electron-donor (D) and acceptor (A) polymers, have drawn attention because of the advantages they hold in the flexibility of choosing the D:A combinations to modulate their energy levels and to improve their overall open-circuit voltages (V oc ) and power conversion efficiencies (PCE)s. V oc is one of the key parameters for the determination of the PCEs of PSCs. In this work, we synthesized six donor polymers with three different side chains appended to the 4,8-di(thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene (BDT) units. By substituting carbon with sulfur and silicon atoms at the 5-position of the thiophenes attached to the BDT units, the highest occupied molecular orbital (HOMO) levels of the donor polymers could be successfully lowered. As anticipated, the V oc values of the resulting all-PSCs increased along with the lowering of the HOMO levels of the donor polymers. Among the six all-PSCs, the PBDT-BDD:PNDI-T10 all-PSC realized a balance between the photovoltage and photocurrent, where a decent PCE of 5.6% was obtained with a V oc of 0.9 V and a photocurrent of 10.5 mA/cm 2 .
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| 3. |
- Anctil, Annick, et al.
(författare)
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Status report on emerging photovoltaics
- 2023
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Ingår i: JOURNAL OF PHOTONICS FOR ENERGY. - : SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS. - 1947-7988. ; 13:4
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Tidskriftsartikel (refereegranskat)abstract
- This report provides a snapshot of emerging photovoltaic (PV) technologies. It consists of concise contributions from experts in a wide range of fields including silicon, thin film, III-V, perovskite, organic, and dye-sensitized PVs. Strategies for exceeding the detailed balance limit and for light managing are presented, followed by a section detailing key applications and commercialization pathways. A section on sustainability then discusses the need for minimization of the environmental footprint in PV manufacturing and recycling. The report concludes with a perspective based on broad survey questions presented to the contributing authors regarding the needs and future evolution of PV.(c) 2023 Society of Photo-Optical Instrumentation Engineers (SPIE)
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| 4. |
- Andersson, Mats R., et al.
(författare)
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Electroluminescence from Substituted Poly(thiophenes) : From Blue to Near-Infrared
- 1995
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Ingår i: Macromolecules. - : American Chemical Society. - 0024-9297 .- 1520-5835. ; 28:22, s. 7525-7529
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Tidskriftsartikel (refereegranskat)abstract
- We report a systematic approach to the control of the conjugation length along the poly(thiophene) backbone. The planarity of the main chain can be permanently modified by altering the pattern of substitution and character of the substituents on the poly(thiophene) chain, and the conjugation length is thus modified. We obtain blue, green, orange, red, and near-infrared electroluminescence from four chemically distinct poly(thiophenes). The external quantum efficiencies are in the range of 0.01-0.6%.
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| 5. |
- Andersson, Mats R., et al.
(författare)
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Improved photoluminescence efficiency of films from conjugated polymers
- 1997
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Ingår i: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 85:1-3, s. 1383-1384
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Tidskriftsartikel (refereegranskat)abstract
- We have demonstrated two general ways to increase the photoluminescence efficiency of films from conjugated polymers. One is to disperse the conjugated polymer on a molecular level by using attractive forces between the conjugated polymer and the matrix. The other method is to substitute the conjugated polymer with side chains which separates the conjugated backbones. Using this idea a new poly(thiophene) with a photoluminescence efficiency of 16% in films has been prepared. LEDs from this polymer exhibit an external efficiency of 0.1% for single layer and 0.7% for double layer diodes.
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| 6. |
- Andersson, Mats R., et al.
(författare)
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Synthesis of poly(alkylthiophenes) for light-emitting diodes
- 1995
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Ingår i: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 71:1-3, s. 2183-2184
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Tidskriftsartikel (refereegranskat)abstract
- We have demonstrated a general way to tune the emission of poly(alkylthiophenes) by using steric interaction between the repeating units. Light-emitting diodes prepared of the polymers have blue to near-infrared emission.
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| 7. |
- Berggren, Magnus, et al.
(författare)
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Controlling inter-chain and intra-chain excitations of a poly(thiophene) derivative in thin films
- 1999
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Ingår i: Chemical Physics Letters. - : Elsevier. - 0009-2614 .- 1873-4448. ; 304:1-2, s. 84-90
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Tidskriftsartikel (refereegranskat)abstract
- The decay of photoexcitations in polythiophene chains has been studied in solid solutions of the polymer from room temperature to 4 K. A strong blue shift of the emission spectrum is observed in the polymer blend, as compared to the homopolymer. Dispersion of the polythiophene suppresses the non-radiative processes, which are suggested to be correlated to close contacts of polymer chains. Quantum chemistry modeling of the excited state distributed on two chains corroborate this conclusion.
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| 8. |
- Berggren, Magnus, et al.
(författare)
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Light-emitting diodes with variable colours from polymer blends
- 1994
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Ingår i: Nature. - : Nature Publishing Group. - 0028-0836 .- 1476-4687. ; 372:6505, s. 444-446
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Tidskriftsartikel (refereegranskat)abstract
- THE range of materials now available for polymer-based light-emitting diodes (LEDs) is such that electroluminescence can be obtained throughout the visible spectrum(1-12). Here we show that, by blending polymers with different emission and charge-transport characteristics, LEDs can be fabricated in which the emission colour varies as a function of the operating voltage. This phenomenon arises from the self-organizing properties of the blends, in which entropy drives phase separation of the constituent polymers and gives rise to submicrometre-sized domains having a range of compositions and emission characteristics. Emission from domains of different composition is controlled by the ease with which charge is injected, which in turn depends on the applied voltage.
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| 9. |
- Berggren, Magnus, et al.
(författare)
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White light from an electroluminescent diode made from poly[3(4‐octylphenyl)‐2,2′‐bithiophene] and an oxadiazole derivative
- 1994
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Ingår i: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 76:11, s. 7530-7534
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Tidskriftsartikel (refereegranskat)abstract
- We report on an electroluminescent diode emitting red, green, and blue light simultaneously. The device is based on a thin polymer layer, poly[3‐(4‐octylphenyl)‐2,2′‐bithiophene] and a thick molecular layer, 2‐(4‐biphenylyl)‐5‐(4‐tertbutyl‐phenyl)1,3,5‐oxadiazole. The quantum efficiency for light conversion is 0.3% and the turn‐on voltage for light emission is 7 V. In this article we present electric and spectroscopic characterizations. A mechanism for the light emission, based on electron and hole recombination between the two organic layers, is proposed
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| 10. |
- Bjorstrom, 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 - art. no. 61921X
- 2006
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Ingår i: Proceedings of SPIE, the International Society for Optical Engineering. - : International Society for Optical Engineering; 1999. - 0277-786X .- 1996-756X. ; 6192, s. X1921-X1921
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Tidskriftsartikel (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-C-61-butyric acid methyl ester (PCBM) are used as the active material in polymer photovoltaic cells. Such blends are known for their tendency to phase separate during film formation. Tuning the morphology 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 solutions before spin-coating on the conversion efficiency of APFO-3:PCBM photodiodes, and related that to the lateral and vertical morphology of thin films of the blend. The lateral morphology is imaged by atomic 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 evaporation of a highly volatile solvent. With addition of the low-vapour pressure solvent chlorobenzene, a more homogeneous vertical composition is found. The conversion efficiency for solar cells of this blend was found to be optimal for chloroform: chlorobenzene mixtures with a volume-ratio of 80:1. We have also investigated the role of the substrate on the morphology. We found that blend films spin-coated from chloroform solutions 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 separation in a region close to the substrate interface.
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| 11. |
- Granström, Magnus, et al.
(författare)
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Phase separation of conjugated polymers - Tools for new functions in polymer LEDs
- 1997
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Ingår i: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 85:1-3, s. 1193-1194
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Tidskriftsartikel (refereegranskat)abstract
- Within the single family of substituted poly(thiophenes) it is possible to realize such diverse device designs as voltage controlled colours from polymer LEDs, sub-micron size LEDs, and white light emitters. Many of these features become possible by the use of polymer blends in which one or more poly(thiophenes) are mixed with a matrix polymer (PMMA). The phase structure in these blends can be controlled by stoichiometry and mode of formation. That phase structure can be used to prevent exciton transfer, and to define new colours in polymer LEDs. It also allows us to make anisotropic conductors suitable for contacting optical devices.
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| 12. |
- Granström, Magnus, et al.
(författare)
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Self organizing polymer films - a route to novel electronic devices based on conjugated polymers
- 1997
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Ingår i: Supramolecular science. - : ELSEVIER SCI LTD. - 0968-5677 .- 1873-4146. ; 4:1-2, s. 27-34
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Tidskriftsartikel (refereegranskat)abstract
- Polymer blends are often used in polymer light emitting diodes as a tool to increase the efficiency of the devices. In this report, we show the necessity to take the phase separation properties of such blends into account, as the miscibility of the involved polymers drastically affects the resulting film structure. By using phase separated polymer blends involving conjugated poly(thiophenes) and different nonconjugated polymers as matrices, different types of applications, such as light emitting diodes with improved voltage control of emitted colour, sub-micron size LEDs and anisotropic conductors are demonstrated. (C) 1997 Elsevier Science Ltd. All rights reserved.
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| 13. |
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| 14. |
- Inganäs, Olle, et al.
(författare)
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Thiophene polymers in light emitting diodes : Making multicolour devices
- 1995
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Ingår i: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 71:1-3, s. 2121-2124
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Tidskriftsartikel (refereegranskat)abstract
- We can control the bandgap of thiophene polymers over 2 eV by choosing the nature, position and regularity of side chain substitutions. Electroluminescence from these polymers cover the full visible spectrum, from the blue into the near infra-red. Blends of these polymer materials allow us to construct voltage controlled variable colour light sources. A newly developed transfer technique allow us to mount thin oriented films of the polymers in polymer LEDs to obtain polarised light sources giving polarisation anisotropys of up to 3. Sub-lambda light sources have been constructed from these polymer materials using nanometer polymer electrodes.
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| 15. |
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| 16. |
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| 17. |
- O Reese, Matthew, et al.
(författare)
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Consensus stability testing protocols for organic photovoltaic materials and devices
- 2011
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Ingår i: SOLAR ENERGY MATERIALS AND SOLAR CELLS. - : Elsevier Science B.V., Amsterdam.. - 0927-0248. ; 95:5, s. 1253-1267
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Tidskriftsartikel (refereegranskat)abstract
- Procedures for testing organic solar cell devices and modules with respect to stability and operational lifetime are described. The descriptions represent a consensus of the discussion and conclusions reached during the first 3 years of the international summit on OPV stability (ISOS). The procedures include directions for shelf life testing, outdoor testing, laboratory weathering testing and thermal cycling testing, as well as guidelines for reporting data. These procedures are not meant to be qualification tests, but rather generally agreed test conditions and practices to allow ready comparison between laboratories and to help improving the reliability of reported values. Failure mechanisms and detailed degradation mechanisms are not covered in this report.
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| 18. |
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| 19. |
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| 20. |
- Teixeira, A.I., et al.
(författare)
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The promotion of neuronal maturation on soft substrates
- 2009
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Ingår i: Biomaterials. - : Elsevier BV. - 0142-9612 .- 1878-5905. ; 30:27, s. 4567-4572
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Tidskriftsartikel (refereegranskat)abstract
- Microenvironmental mechanical properties of stem cell niches vary across tissues and developmental stages. Accumulating evidence suggests that matching substrate elasticity with in vivo tissue elasticity facilitates stem cell differentiation. However, it has not been established whether substrate elasticity can control the maturation stage of cells generated by stem cell differentiation. Here we show that soft substrates with elasticities commensurable to the elasticity of the brain promote the maturation of neural stem cell-derived neurons. In the absence of added growth factors, neurons differentiated on soft substrates displayed long neurites and presynaptic terminals, contrasting with the bipolar immature morphology of neurons differentiated on stiff substrates. Further, soft substrates supported an increase in astrocytic differentiation. However, stiffness cues could not override the dependency of astrocytic differentiation on Notch signaling. These results demonstrate that substrate elasticity per se can drive neuronal maturation thus defining a crucial parameter in neuronal differentiation of stem cells.
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| 21. |
- Vandamme, P. A., et al.
(författare)
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Bordetella bronchialis sp nov., Bordetella flabilis sp nov and Bordetella sputigena sp nov., isolated from human respiratory specimens, and reclassification of Achromobacter sediminum Zhang et al. 2014 as Verticia sediminum gen. nov., comb. nov
- 2015
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Ingår i: International Journal of Systematic and Evolutionary Microbiology. - : Microbiology Society. - 1466-5026 .- 1466-5034. ; 65, s. 3674-3682
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Tidskriftsartikel (refereegranskat)abstract
- The phenotypic and genotypic characteristics of four Bordetella hinzii-like strains from human respiratory specimens and representing nrdA gene sequence based genogroups 3, 14 and 15 were examined. In a 16S rRNA gene sequence based phylogenetic tree, the four strains consistently formed a single coherent lineage but their assignment to the genus Bordetella was equivocal. The respiratory quinone, polar lipid and fatty acid profiles generally conformed to those of species of the genus Bordetella and were characterized by the presence of ubiquinone 8, of phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol and several aminolipids, and of high percentages of C-16 : 0, cyclo-C-17 : 0 and summed feature 2, as major chemotaxonomic marker molecules, respectively. The DNA G+C content was about 66 mol%, which corresponded with that of the high-percentage DNA G+C content genera of the family Alcaligenaceae including the genus Bordetella. DNA DNA hybridiiation experiments revealed the presence of three distinct genomospecies and thus confirmed phenotypic differences as revealed by means of extensive biochemical characterization. We therefore propose to formally classify Bordetella genogroups 3, 14 and 15 as Bordetella bronchialis sp. nov. (type strain LMG 28640(T)=AU3182(T)=CCUG 56828(T)), Bordetella sputigena sp. nov. (type strain LMG 28641(T)=CCUG 56478(T)) and Bordetella flabilis sp. nov. (type strain LMG 28642(T)=AU10664(T)=CCUG 56827(T)). In addition, we propose to reclassify Achromobacter sediminum into the novel genus Verticia, as Verticia sediminum, gen. nov., comb. nov., on the basis of its unique phylogenetic position, its marine origin and its distinctive phenotypic, fatty acid and polar lipid profile.
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| 22. |
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