| 31. |
- Andersson, Mattias, et al.
(author)
-
Mobility and fill factor correlation in geminate recombination limited solar cells
- 2011
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In: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 110:2, s. 024509-
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Journal article (peer-reviewed)abstract
- Empirical data for the fill factor as a function of charge carrier mobility for two different polymer: fullerene systems is presented and analyzed. The results indicate that charge extraction depth limitations and space charge effects are inconsistent with the observed behavior, and the decrease in the fill factor is, instead, attributed to the field-dependent charge separation and geminate recombination. A solar cell photocurrent limited by the Onsager-Braun charge transfer exciton dissociation is shown to be able to accommodate the experimental observations. Charge dissociation limited solar cells always benefit from increased mobilities, and the negative contribution from the reduced charge separation is shown to be much more important for the fill factor in these material systems than any adverse effects from charge carrier extraction depth limitations or space charge effects due to unbalanced mobilities. The logarithmic dependence of the fill factor on the mobility for such a process is also shown to imply that simply increasing the mobilities is an impractical way to reach very high fill factors under these conditions since unrealistically high mobilities are required. A more controlled morphology is, instead, argued to be necessary for high performance.
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| 32. |
- Andersson, Mats R., et al.
(author)
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Electroluminescence from Substituted Poly(thiophenes) : From Blue to Near-Infrared
- 1995
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In: Macromolecules. - : American Chemical Society. - 0024-9297 .- 1520-5835. ; 28:22, s. 7525-7529
-
Journal article (peer-reviewed)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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| 33. |
- Andersson, Mats R., et al.
(author)
-
Improved photoluminescence efficiency of films from conjugated polymers
- 1997
-
In: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 85:1-3, s. 1383-1384
-
Journal article (peer-reviewed)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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| 34. |
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| 35. |
- Andersson, Mats R., et al.
(author)
-
Regioselective polymerization of 3-(4-octylphenyl)thiophene with FeCl3
- 1994
-
In: Macromolecules. - : American Chemical Society. - 0024-9297 .- 1520-5835. ; 27:22, s. 6503-6506
-
Journal article (peer-reviewed)abstract
- We have shown that it is possible to regioselectively polymerize 3-(4-octylphenyl) thiophene with FeCl3. Adding FeCl3 slowly to the monomer leads to a soft and therefore regioselective polymerization. The head-to-tail content was determined by H-1 NMR to be 94 +/- 2%. Thin films of the polymer treated with chloroform vapor have an absorption maximum at 602 nm (2.06 eV) with clear vibronic fine structure. Free standing films have a conductivity of 4 S/cm, which is 100 times higher than for earlier prepared poly(3-(4-octylphenyl)thiophene). A mechanism for the regioregular polymerization is also proposed.
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| 36. |
- Andersson, Mats R., et al.
(author)
-
Synthesis of poly(alkylthiophenes) for light-emitting diodes
- 1995
-
In: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 71:1-3, s. 2183-2184
-
Journal article (peer-reviewed)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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| 37. |
- Andersson, M.R., et al.
(author)
-
The effect of the polymerisation temperature on molecular weight and photoluminescence quantum yield for a phenylsubstituted PPV
- 2001
-
In: Synthetic metals. - 0379-6779 .- 1879-3290. ; 119:1-3, s. 63-64
-
Journal article (peer-reviewed)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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| 38. |
- Andersson, Mattias, et al.
(author)
-
Unified Study of Recombination in Polymer:Fullerene Solar Cells Using Transient Absorption and Charge-Extraction Measurements
- 2013
-
In: Journal of Physical Chemistry Letters. - : American Chemical Society. - 1948-7185 .- 1948-7185. ; 4:12, s. 2069-2072
-
Journal article (peer-reviewed)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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| 39. |
- Andersson, Viktor, et al.
(author)
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An optical spacer is no panacea for light collection in organic solar cells
- 2009
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In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 94:4, s. 043302-
-
Journal article (peer-reviewed)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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| 40. |
- Andersson, Viktor, et al.
(author)
-
Comparative study of organic thin film tandem solar cells in alternative geometries
- 2008
-
In: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 104:12, s. 124508-
-
Journal article (peer-reviewed)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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