| 1. |
- Ding, L., et al.
(författare)
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Photovoltaic cells with a conjugated polyelectrolyte
- 2000
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Ingår i: Synthetic metals. - 0379-6779 .- 1879-3290. ; 110:2, s. 133-140
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Tidskriftsartikel (refereegranskat)abstract
- We describe photovoltaic cells made from a novel conjugated polyelectrolyte, the lithium salt of poly(thiophene-3-acetic acid) (PTAA-Li). The aqueous solubility of this polyelectrolyte allows formation of blend electrodes with a dispersion of the metallic polymer Poly(Ethylene DiOxyThiophene) (PEDOT). The incident monochromatic photon to current conversion efficiency (IPCE) of the cells were improved up to 19% by blending PTAA-Li with PEDOT to modify the ITO electrode, in combination with the low bandgap polymer poly(3-(4-octylphenyl)thiophene) (POPT), and C60 as electron acceptor. We attribute the increase of efficiency to the improved contact area between the conjugated polyelectrolyte and PEDOT.
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| 2. |
- Arias, A.C., et al.
(författare)
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Use of tin oxide thin films as a transparent electrode in PPV based light-emitting diodes
- 2000
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Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 371:1, s. 201-206
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Tidskriftsartikel (refereegranskat)abstract
- Tin oxide (TO) thin films, nominally undoped, have been used as electrodes in poly(p-phenylene vinylene) (PPV) based organic electroluminescent devices. The evolution of the crystallinity and the electrical resistance of TO films submitted to the PPV thermal conversion conditions, have been investigated. It has been found that the electrical resistance is decreased whereas the crystallinity of the film is increased. It is shown in this work, that the photoluminescence of PPV converted on top of TO substrates is not as quenched as it is when converted on top of indium-tin oxide (ITO) substrates. The quantum efficiency of light-emitting diode is 0.07% at 17 V forward bias. It is also shown that the work function of TO films is very stable to different cleaning procedures, in contrast with previous results obtained for ITO films.
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| 3. |
- Da, Silva A.F., et al.
(författare)
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Asymmetric nonlinear amplitude in patterns of porous silicon
- 2000
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Ingår i: Physica A. - 0378-4371 .- 1873-2119. ; 283:1, s. 223-227
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Tidskriftsartikel (refereegranskat)abstract
- A gradient pattern analysis is used to report a phenomenogical evidence of asymmetric nonlinear spatial distribution of porous silicon structures. We used a canonical sample set obtained from scanning force microscopy. Due to the high sensitivity of the gradient field operator, it is possible to correlate the photoluminescence performance of porous silicon with different degree of asymmetries and spatial nonlinearity. A generalization of this new approach to quantify nonlinear amplitude fragmentation in complex lattices is proposed.
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| 4. |
- Ferreira, Da Silva A., et al.
(författare)
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Characterization of asymmetric fragmentation patterns in SFM images of porous silicon
- 2000
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Ingår i: Solid State Communications. - 0038-1098 .- 1879-2766. ; 113:12, s. 703-708
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Tidskriftsartikel (refereegranskat)abstract
- Due to possible technological applications in opto-electronic devices, the interest in characterizing porous silicon structure patterns has recently increased. From scanning force microscopy (SFM) we have obtained images of different samples of porous silicon and applied pattern characterization operators on these matrices. In this paper, asymmetric spatial fragmentation in amplitude envelopes of porous silicon samples are characterized by means of a parameter that quantifies the amount of spatial asymmetry in the gradient field. The results show that this method is well suited to characterize silicon porosity quantitatively.
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| 5. |
- Inganäs, Olle, et al.
(författare)
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Recent progress in thin film organic photodiodes
- 2001
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Ingår i: Synthetic metals. - 0379-6779 .- 1879-3290. ; 121:1-3, s. 1525-1528
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Tidskriftsartikel (refereegranskat)abstract
- We review current developments in organic photodiodes, with special reference to multilayer thin film optics, and modeling of organic donor-acceptor photodiodes. We indicate possibilities to enhance light absorption in devices by nanopatterning as well as by blending, and also discuss materials science issues of nanostructure in blends and in vertically stratified multilayer devices. Our current best devices have external efficiencies of 30-50% in between 400-600 nm, and show fill factors of 0.54 illuminated under weak monochromatic light.
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| 6. |
- Jonforsen, M., et al.
(författare)
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Photodiodes made from poly(pyridopyrazine vinylene) : polythiophene blends
- 2001
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Ingår i: Synthetic metals. - 0379-6779 .- 1879-3290. ; 119:1-3, s. 185-186
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Tidskriftsartikel (refereegranskat)abstract
- A PPV-type polymer with the pyridopyrazine heterocycle (EHH-PPyPzV) has been synthesised and found to have high electron affinity according to electrochemical measurements. When used as the electron accepting material in single-layer-photodiodes, with a thiophene copolymer (PEOPT-co-PAAPT) as the electron donating material, IPCE (incident photon to current conversion efficiency) up to 1% was measured. Atomic force microscopy was used to analyse the blend morphology in the devices.
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| 7. |
- Koehler, M., et al.
(författare)
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Modeling bilayer polymer/fullerene photovoltaic devices
- 2004
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 96:1, s. 40-43
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Tidskriftsartikel (refereegranskat)abstract
- The electrical transport and charge generation of polymer/fullerene photovoltaic devices were investigated. The polymer/fullerene photodiodes were formed by a heterojunction of fullerene and a semiconducting polymer poly (3,4-ethylenedioxythiophene). The current-voltage characteristic of the devices were measured with variable thickness of the C60 layer, under monochromatic light of different wavelengths. The results show that the values of the electrical photoconductivity are related to the optical absorption coefficient of the fullerene, and thus implying a large contribution of the C60 films to the diode photocurrent.
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| 8. |
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| 9. |
- Nielsen, Michael L., et al.
(författare)
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Physicochemical properties determining the detection probability of tryptic peptides in Fourier transform mass spectrometry. A correlation study
- 2004
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 76:19, s. 5872-5877
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Tidskriftsartikel (refereegranskat)abstract
- Sequence verification and mapping of posttranslational modifications require nearly 100% sequence coverage in the "bottom-up" protein analysis. Even in favorable cases, routine liquid chromatography-mass spectrometry detects from protein digests peptides covering 50-90% of the sequence. Here we investigated the reasons for limited peptide detection, considering various physicochemical aspects of peptide behavior in liquid chromatography-Fourier transform mass spectrometry (LC-FTMS). No overall correlation was found between the detection probability and peptide mass. In agreement with literature data, the signal increased with peptide hydrophobicity. Surprisingly, the pI values exhibited an opposite trend, with more acidic tryptic peptides detected with higher probability. A mixture of synthesized peptides of similar masses confirmed the hydrophobicity dependence but showed strong positive correlation between pI and signal response. An explanation of this paradoxal behavior was found through the observation that more acidic tryptic peptide lengths tend to be longer. Longer peptides tend to acquire higher average charge state in positive mode electrospray ionization than more basic but shorter counterparts. The induced-current detection in FTMS favors ions in higher charge states, thus providing the observed pI-FTMS signal anticorrelation.
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| 10. |
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| 11. |
- Pettersson, Lars, et al.
(författare)
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Quantum efficiency of exciton-to-charge generation in organic photovoltaic devices
- 2001
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 89:10, s. 5564-5569
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 12. |
- Roman, L.S., et al.
(författare)
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Charge carrier mobility in substituted polythiophene-based diodes
- 2001
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Ingår i: Synthetic metals. - 0379-6779 .- 1879-3290. ; 125:3, s. 419-422
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the transport properties of the semiconducting polymer poly(3-(2'-methoxy-5'-octylphenyl)thiophene) (POMeOPT). We have measured the current-voltage (C-V) characteristics of single polymer layer devices in two regimes contact limited current and bulk-limited current. The passage from one regime to the other was done upon insertion of a conducting polymer poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) (PEDOT-PSS) between the metallic electrode and the semiconducting polymer. With PEDOT-PSS as electrode, the polymer gave space-charge limited current (SCLC) with the mobility dependent on electric field. Fitting the data, we were able to obtain important parameters, such as the zero-field mobility and the characteristic field. We have compared our results with the well-studied polymer poly(2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene) (MEH-PPV) in similar experiments earlier reported. © 2001 Elsevier Science B.V. All rights reserved.
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| 13. |
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