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Pettersson, Lars
Publications (10 of 13) Show all publications
Marcus, C. & Pettersson, L. (2005). UTD analysis of faceted conformal antenna arrays of dipoles. In: European Workshop on Conformal Antennas,2005 (pp. 23). Stockholm: Universitetsservice US AB
Open this publication in new window or tab >>UTD analysis of faceted conformal antenna arrays of dipoles
2005 (English)In: European Workshop on Conformal Antennas,2005, Stockholm: Universitetsservice US AB , 2005, p. 23-Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
Stockholm: Universitetsservice US AB, 2005
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-31896 (URN)17729 (Local ID)17729 (Archive number)17729 (OAI)
Available from: 2009-10-09 Created: 2009-10-09
Johansson, T., Pettersson, L. & Inganäs, O. (2002). Conductivity of de-doped poly(3,4-ethylenedioxythiophene). Synthetic metals, 129(3), 269-274
Open this publication in new window or tab >>Conductivity of de-doped poly(3,4-ethylenedioxythiophene)
2002 (English)In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 129, no 3, p. 269-274Article in journal (Refereed) Published
Abstract [en]

The conductivity of chemically and electrochemically de-doped poly(3,4-ethylenedioxythiophene) (PEDOT) has been investigated in situ. We observe a decrease in the conductivity by 4-5 orders of magnitude. The change of conductivity is correlated to the change of electronic structure. We obtain the dielectric function of the polymer by spectroscopic ellipsometry and note that anisotropy is observed in both doped and neutral states. © 2002 Elsevier Science B.V. All rights reserved.

Keywords
Conductivity, Electrochemical doping, Ellipsometry, PEDOT, Spectroscopy
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-46927 (URN)10.1016/S0379-6779(02)00086-3 (DOI)
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-13
Pettersson, L., Ghosh, S. & Inganäs, O. (2002). Optical anisotropy in thin films of poly(3,4-ethylenedioxythiophene)- poly(4-styrenesulfonate). Organic electronics, 3(3-4), 143-148
Open this publication in new window or tab >>Optical anisotropy in thin films of poly(3,4-ethylenedioxythiophene)- poly(4-styrenesulfonate)
2002 (English)In: Organic electronics, ISSN 1566-1199, E-ISSN 1878-5530, Vol. 3, no 3-4, p. 143-148Article in journal (Refereed) Published
Abstract [en]

Anisotropic optical constants spectrum of spin-coated thin films of poly(3,4-ethylenedioxythiophene)-poly(4-styrenesulfonate) (PEDOT-PSS) from 200 to 1700 nm were determined using variable-angle spectroscopic ellipsometry and polarized intensity transmission data together with absorption spectroscopy. PEDOT-PSS was found to be very anisotropic, uniaxial with the optic axis parallel to the surface normal. The result is in good agreement with results obtained of chemically polymerized PEDOT layers doped with toluenesulfonate. By adding sorbitol to the PEDOT-PSS dispersion before spin-coating, layers with a higher conductivity were obtained. A detailed study was made of the optical response of these layers in comparison to the PEDOT-PSS prepared from dispersions without sorbitol. The optical anisotropy is important to consider when using PEDOT-PSS in optoelectronic devices, such as polymer light-emitting diodes and photovoltaic devices. © 2002 Elsevier Science B.V. All rights reserved.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-46828 (URN)10.1016/S1566-1199(02)00051-4 (DOI)
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-13
Granlund, T., Pettersson, L. & Inganäs, O. (2001). Determination of the emission zone in a single-layer polymer light-emitting diode through optical measurements. Journal of Applied Physics, 89(11), 5897-5902
Open this publication in new window or tab >>Determination of the emission zone in a single-layer polymer light-emitting diode through optical measurements
2001 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 89, no 11, p. 5897-5902Article in journal (Refereed) Published
Abstract [en]

We study the emission zone in a single-layer polymer light-emitting diode. The emission zone is found by studying the angular distribution of the electroluminescence. The emission is modeled by accounting for optical interference. We account for birefringence of the anode layer in our model. The active polymer was, however, found to be isotropic. The anode consists of a single-layer of the conducting polymer complex poly(3,4-ethylenedioxythiophene) and poly(styrene sulfonate) (PEDOT-PSS), with enhanced conductivity. As a cathode we use plain aluminum. By using only PEDOT-PSS we avoid having a thin metal layer or indium-tin-oxide as the anode in the path of the escaping light. The active material is a substituted polythiophene with excellent film forming properties. A comparison between the experimental and calculated angular distribution of light emission from a single-layered polymer light-emitting diode was shown to be in good agreement for the spectral region studied. By assuming a distribution of the emission zone, we deduce the position as well as the width of the zone. (C) 2001 American Institute of Physics.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-49229 (URN)
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-12
Greczynski, G., Johansson, N., Logdlund, M., Pettersson, L., Salaneck, W. R., Horsburgh, L., . . . Bredas, J. (2001). Electronic structure of pristine and sodium doped poly(p-pyridine). Journal of Chemical Physics, 114(9), 4243-4252
Open this publication in new window or tab >>Electronic structure of pristine and sodium doped poly(p-pyridine)
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2001 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 114, no 9, p. 4243-4252Article in journal (Refereed) Published
Abstract [en]

Ultraviolet spectroscopy (UPS) and x-ray photoelectron spectroscopy (XPS) were used to study the valence electronic structures of pristine and sodium doped poly (p-pyridine) (PPY). The UPS spectra were analyzed by studying the density-of-valence-states (DOVS) derived from quantum chemical calculations. The electronic band structure of the PPY chains was also theoretically investigated using the valence effective Hamiltonian (VEH) method. The theoretical approach was found to be more accurate in describing the electronic structure of PPY.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-47464 (URN)10.1063/1.1343485 (DOI)
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-13
Pettersson, L., Roman, L. & Inganäs, O. (2001). Quantum efficiency of exciton-to-charge generation in organic photovoltaic devices. Journal of Applied Physics, 89(10), 5564-5569
Open this publication in new window or tab >>Quantum efficiency of exciton-to-charge generation in organic photovoltaic devices
2001 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 89, no 10, p. 5564-5569Article in journal (Refereed) Published
Abstract [en]

We present an analysis of the internal monochromatic quantum efficiency of photovoltaic devices based on polymer and polymer/fullerene thin films. A quantum efficiency of exciton-to-charge generation is defined as the external monochromatic quantum efficiency normalized to the absorption in the active materials of the device. An upper limit of the efficiency can be determined, and results show that much of the light is absorbed in photoactive layers of the device, whereas only a fraction of the generated excitons is converted to charge carriers and can be collected as photocurrent. © 2001 American Institute of Physics.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-47382 (URN)10.1063/1.1359425 (DOI)
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-13
Samuelsen, E., Monkman, A., Pettersson, L., Horsburgh, L., Aasmundtveit, K. & Ferrer, S. (2001). The structure of polypyridine. Synthetic metals, 124(2-3), 393-398
Open this publication in new window or tab >>The structure of polypyridine
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2001 (English)In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 124, no 2-3, p. 393-398Article in journal (Refereed) Published
Abstract [en]

X-ray diffraction on samples in the form of a deposited thin layer, a crushed powder and a flake were used to deduce models for the crystalline structure of polypyridine (-(C5H3N)n-), a conjugated polymer of great interest for applications. A monoclinic unit cell with lattice parameters a = 7.47 Å, b = 5.83 Å, c = 4.25 Å, ? = 108.7° containing two chains running along the c-axis and with the molecular plane normal to the a-axis gives a good fit with the observations. The interchain packing distance is about 3.6 Å, i.e. in the same range as intermolecular distances found in conductive charge transfer salts. The deposited layer is highly anisotropic, with the a-c-plane parallel to the substrate. © 2001 Elsevier Science B.V. All rights reserved.

Keywords
Anisotropy, Conjugated polymers, Crystalline structure, X-ray diffraction
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-47239 (URN)10.1016/S0379-6779(01)00378-2 (DOI)
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-13
Martin, T. & Pettersson, L. (2000). Dispersion compensation for Huygens' sources and far-zone transformation in FDTD. IEEE Transactions on Antennas and Propagation, 48(4), 494-501
Open this publication in new window or tab >>Dispersion compensation for Huygens' sources and far-zone transformation in FDTD
2000 (English)In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 48, no 4, p. 494-501Article in journal (Refereed) Published
Abstract [en]

The equivalence principle is utilized for generation of both incident plane waves and for near- to far-zone transformation in the finite-difference time-domain (FDTD) method. Small errors will appear due to numerical dispersion when a plane wave is generated by Huygens' sources using an analytical expression fur the incident field. These errors can be derived from the numerical dispersion relation in the frequency domain. By using a second-order approximation of the numerical wavenumber it is shown that a simple approximative time-domain compensation procedure for the dispersion can be derived. This has been implemented in a Huygens' source routine and in a time-domain near- to far-zone transformation routine. It is shown that this compensation significantly reduces the errors produced when calculating far-zone scattered fields of low amplitude. It is also shown that it is sufficient to compensate either the Huygens' sources or the time-domain near- to Far-zone transformation with respect to dispersion. For validation, plane wave propagation through empty space and scattering of a dipole have been studied.

Keywords
FDTD methods, numerical dispersion
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-49723 (URN)
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-12
Granlund, T., Pettersson, L., Andersson, M. & Inganäs, O. (2000). Luminescence probing of crystallization in a polymer film. Journal of Applied Physics, 87(12), 8549-8556
Open this publication in new window or tab >>Luminescence probing of crystallization in a polymer film
2000 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 87, no 12, p. 8549-8556Article in journal (Refereed) Published
Abstract [en]

We report studies of a thin film multilayer stack including a highly emissive substituted polythiophene, poly[3-(2,5-dioctylphenyl)thiophene]. Analysis of the photoluminescence spectra revealed an inhomogeneous polymer film. X-ray diffraction studies attribute the existence of an inhomogeneous film as originating from crystallization of the polymer. We used the interference effect of light to detect the region of crystallization in the film. Photoluminescence and absorption were redshifted upon crystallization and displayed an enhanced vibronic structure. Comparison between calculated and measured photoluminescence shows that the crystallization starts from the top of the film and not from the supporting substrate. (C) 2000 American Institute of Physics. [S0021- 8979(00)08112-3].

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-49737 (URN)
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-12
Aasmundtveit, K., Samuelsen, E., Guldstein, M., Steinsland, C., Flornes, O., Fagermo, C., . . . Ferrer, S. (2000). Structural anisotropy of poly(alkylthiophene) films. Macromolecules, 33(8), 3120-3127
Open this publication in new window or tab >>Structural anisotropy of poly(alkylthiophene) films
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2000 (English)In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 33, no 8, p. 3120-3127Article in journal (Refereed) Published
Abstract [en]

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.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-47663 (URN)10.1021/ma991631k (DOI)
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-13
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