| 31. |
- Andersson, M.R., et al.
(författare)
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The effect of the polymerisation temperature on molecular weight and photoluminescence quantum yield for a phenylsubstituted PPV
- 2001
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Ingår i: Synthetic metals. - 0379-6779 .- 1879-3290. ; 119:1-3, s. 63-64
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Tidskriftsartikel (refereegranskat)abstract
- We present the synthesis and characterisation of poly(2-(2',5'-bis(2?-ethylhexyloxy)phenyl)-1, 4-phenylenevinylene) (BEHP-PPV) polymerised under different conditions. The photoluminescence efficiencies (?PL) in the solid state of BEHP-PPV obtained at 144°C and 0°C are 28% and 60%, respectively. Polymerisation temperatures below 0°C decreases the molecular weight without changing the photoluminescence efficiency to any large extent.
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| 32. |
- Andersson, Mattias, et al.
(författare)
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Unified Study of Recombination in Polymer:Fullerene Solar Cells Using Transient Absorption and Charge-Extraction Measurements
- 2013
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Ingår i: Journal of Physical Chemistry Letters. - : American Chemical Society. - 1948-7185 .- 1948-7185. ; 4:12, s. 2069-2072
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Tidskriftsartikel (refereegranskat)abstract
- Recombination in the well-performing bulk heterojunction solar cell blend between the conjugated polymer TQ-1 and the substituted fullerene PCBM has been investigated with pump-probe transient absorption and charge extraction of photo-generated carriers (photo-CELIV). Both methods are shown to generate identical and overlapping data under appropriate experimental conditions. The dominant type of recombination is bimolecular with a rate constant of 7 x 10(-12) cm(-3) s(-1). This recombination rate is shown to be fully consistent with solar cell performance. Deviations from an ideal bimolecular recombination process, in this material system only observable at high pump fluences, are explained with a time-dependent charge-carrier mobility, and the implications of such a behavior for device development are discussed.
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| 33. |
- Andersson, Viktor, et al.
(författare)
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An optical spacer is no panacea for light collection in organic solar cells
- 2009
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 94:4, s. 043302-
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Tidskriftsartikel (refereegranskat)abstract
- The role of an optical spacer layer has been examined by optical simulations of organic solar cells with various bandgaps. The simulations have been performed with the transfer matrix method and the finite element method. The results show that no beneficial effect can be expected by adding an optical spacer to a solar cell with an already optimized active layer thickness.
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| 34. |
- Andersson, Viktor, et al.
(författare)
-
Comparative study of organic thin film tandem solar cells in alternative geometries
- 2008
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 104:12, s. 124508-
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Tidskriftsartikel (refereegranskat)abstract
- Optical modeling of one folded tandem solar cell and four types of stacked tandem solar cells has been performed using the finite element method and the transfer matrix method for the folded cell and the stacked cells, respectively. The results are analyzed by comparing upper limits for short circuit currents and power conversion efficiencies. In the case of serial connected tandems all of the five cell types may be compared, and we find that the folded cells are comparable to stacked tandem cells in terms of currents and power conversion efficiencies.
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| 35. |
- Andersson, Viktor, et al.
(författare)
-
Full day modelling of V-shaped organic solar cell
- 2011
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Ingår i: Solar Energy. - : Elsevier Science B.V., Amsterdam.. - 0038-092X .- 1471-1257. ; 85:6, s. 1257-1263
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Tidskriftsartikel (refereegranskat)abstract
- Folded and planar solar cells are examined with optical simulations, with the finite element method. The maximum photocurrent densities during the full day are compared between cells of different geometries and tilting angles. The change of incident angle and spectrum over time are handled in this analysis. The results show that the light trapping effect of the folded cell makes these cells show higher maximum photocurrent densities than the planar cells during all hours of the day. This is the case for both single and tandem cells. The results also indicate that balancing the currents in the tandem cells by adjusting the active layer thickness may be more cumbersome with the folded tandem cells than the stacked planar cells.
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| 36. |
- Andersson, Viktor, et al.
(författare)
-
Imaging of the 3D Nanostructure of a Polymer Solar Cell by Electron Tomography
- 2009
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Ingår i: Nano letters (Print). - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 9:2, s. 853-855
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Tidskriftsartikel (refereegranskat)abstract
- Electron tomography has been used for analyzing the active layer in a polymer solar cell, a bulk heterojunction of an alternating copolymer of fluorene and a derivative of fullerene. The method supplies a three-dimensional representation of the morphology of the film, where domains with different scattering properties may be distinguished. The reconstruction shows good contrast between the two phases included in the film and demonstrates that electron tomography is an adequate tool for investigations of the three-dimensional nanostructure of the amorphous materials used in polymer solar cells.
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| 37. |
- Andersson, Viktor, et al.
(författare)
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Morphology of organic electronic materials imaged via electron tomography
- 2012
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Ingår i: Journal of Microscopy. - : Wiley. - 0022-2720 .- 1365-2818. ; 247:3, s. 277-287
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Tidskriftsartikel (refereegranskat)abstract
- Several organic materials and blends have been studied with the use of electron tomography. Tomography reconstructions of active layers of organic solar cells, where various preparation techniques have been used, have been analysed and compared to device behaviour. In addition, materials with predefined structures, including contrast enhancing features, have been studied and double tilt data collection has been employed to improve reconstructions. Small changes in preparation procedures may lead to large differences in morphology and device performance, and the results also indicate a complex relation between these.
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| 38. |
- Andersson, Viktor, et al.
(författare)
-
Optical modeling of a folded organic solar cell
- 2008
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 103:9, s. 094520-
-
Tidskriftsartikel (refereegranskat)abstract
- The optical behavior of a reflective tandem solar cell (V cell) is modeled by means of finite element method (FEM) simulations. The absorption of solar light in the active material as well as in both electrode layers is calculated. The FEM solves the electromagnetic wave equation on the entire defined geometry, resulting in the consideration of interference effects, as well as effects of refraction and reflection. Both single cells and tandem cells are modeled and confirmed to be in accordance with reflectance measurements. Energy dissipation in the active layers is studied as a function of layer thickness and folding angle, and the simulations clearly display the advantage of the light trapping feature of folded cells. This is especially prominent in cells with thinner active layers, where folding induces absorption in the active layer equivalent to that of much thicker cells.
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| 39. |
- Asberg, D.P., et al.
(författare)
-
PEDOT/PSS hydrogel networks as 3-D enzyme electrodes
- 2003
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Konferensbidrag (refereegranskat)abstract
- A mesoscopic network in the form of a hydrogel of the highly conductive polymer PEDOT/PSS hydrogel was used in an enzyme electrode setup. Osmium was used both as a crosslink point in the hydrogel network and as a mediator between the prosthetic group of the enzyme and the conductive polymer matrix. Both biostability and high conductivity is important aspects when building nerve- or cell- electrodes. Diffusion of analytes surrounding the cells into the matrix electrode is feasible due to the open hydrogel structure. The high water content in these structures is important when buffering them to a pH of choice.
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| 40. |
- Asplund, Maria, 1978-, et al.
(författare)
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Composite biomolecule/PEDOT materials for neural electrodes
- 2008
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Ingår i: Biointerphases. - NY : American Institute of Physics. - 1559-4106 .- 1934-8630. ; 3:3, s. 83-93
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Tidskriftsartikel (refereegranskat)abstract
- Electrodes intended for neural communication must be designed to meet boththe electrochemical and biological requirements essential for long term functionality. Metallic electrode materials have been found inadequate to meet theserequirements and therefore conducting polymers for neural electrodes have emergedas a field of interest. One clear advantage with polymerelectrodes is the possibility to tailor the material to haveoptimal biomechanical and chemical properties for certain applications. To identifyand evaluate new materials for neural communication electrodes, three chargedbiomolecules, fibrinogen, hyaluronic acid (HA), and heparin are used ascounterions in the electrochemical polymerization of poly(3,4-ethylenedioxythiophene) (PEDOT). The resultingmaterial is evaluated electrochemically and the amount of exposed biomoleculeon the surface is quantified. PEDOT:biomolecule surfaces are also studiedwith static contact angle measurements as well as scanning electronmicroscopy and compared to surfaces of PEDOT electrochemically deposited withsurfactant counterion polystyrene sulphonate (PSS). Electrochemical measurements show that PEDOT:heparinand PEDOT:HA, both have the electrochemical properties required for neuralelectrodes, and PEDOT:heparin also compares well to PEDOT:PSS. PEDOT:fibrinogen isfound less suitable as neural electrode material.
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