| 1. |
- Krebs, Frederik C, et al.
(författare)
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A round robin study of flexible large-area roll-to-roll processed polymer solar cell modules
- 2009
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Ingår i: SOLAR ENERGY MATERIALS AND SOLAR CELLS. - : Elsevier BV. - 0927-0248. ; 93:11, s. 1968-1977
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Tidskriftsartikel (refereegranskat)abstract
- A round robin for the performance of roll-to-roll coated flexible large-area polymer solar-cell modules involving 18 different laboratories in Northern America, Europe and Middle East is presented. The study involved the performance measurement of the devices at one location (Riso DTU) followed by transportation to a participating laboratory for performance measurement and return to the starting location (Riso DTU) for re-measurement of the performance. It was found possible to package polymer solar-cell modules using a flexible plastic barrier material in such a manner that degradation of the devices played a relatively small role in the experiment that has taken place over 4 months. The method of transportation followed both air-mail and surface-mail paths.
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| 2. |
- Jan Anton Koster, L., et al.
(författare)
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Quantifying Bimolecular Recombination Losses in Organic Bulk Heterojunction Solar Cells
- 2011
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Ingår i: Advanced Materials. - : Wiley-VCH Verlag. - 0935-9648 .- 1521-4095. ; 23:14, s. 1670-
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Tidskriftsartikel (refereegranskat)abstract
- We present a new experimental technique that affords direct quantification of the fraction of charge carriers lost in poly(3-hexylthiophene): fullerene solar cells by bimolecular recombination. Depending on annealing conditions up to 17% of carriers recombine bimolecularly under solar illumination. We explain our findings with a closed analytical expression for the photocurrent generated by an organic solar cell.
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| 3. |
- Maturova, Klara, et al.
(författare)
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Description of the Morphology Dependent Charge Transport and Performance of Polymer:Fullerene Bulk Heterojunction Solar Cells
- 2011
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Ingår i: Advanced Functional Materials. - : Wiley-VCH Verlag. - 1616-301X .- 1616-3028. ; 21:2, s. 261-269
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Tidskriftsartikel (refereegranskat)abstract
- We present a combined numerical charge transport and morphology model to describe the current density-voltage (j-V) characteristics of three different, benchmark polymer: fullerene bulk heterojunction organic solar cells in which the device performance critically depends on the processing conditions or composition of the active layer. We find that an accurate description of the j-V characteristics over a broad bias range can be obtained when the actual complex, three-dimensional (3D) phase separation is represented by a simplified 2D or even 1D description. The morphological device model allows predicting the potential for increasing device performance by further optimizing the morphology. The optimal simplified morphology consists of two, relatively thin alternating vertically oriented slabs, that allow for fast lateral separation of photocreated holes and electrons. This morphology can effectively be described as 1D.
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| 4. |
- Maturova, Klara, et al.
(författare)
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Scanning Kelvin Probe Microscopy on Bulk Heterojunction Polymer Blends
- 2009
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Ingår i: Advanced Functional Materials. - : Wiley-VCH Verlag. - 1616-301X .- 1616-3028. ; 19:9, s. 1379-1386
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Tidskriftsartikel (refereegranskat)abstract
- Here, correlated AFM and scanning Kelvin probe microscopy measurements with sub-100 nm resolution on the phase-separated active layer of polymer-fullerene (MDMO-PPV:PCBM) bulk heterojunction solar cells in the dark and under illumination are described. Using numerical modeling a fully quantitative explanation for the contrast and shifts of the surface potential in dark and light is provided. Under illumination an excess of photogenerated electrons is present in both the donor and acceptor phases. From the time evolution of the surface potential after switching off the light the contributions of free and trapped electrons can be identified. Based on these measurements the relative 3D energy level shifts of the sample are calculated. Moreover, by comparing devices with fine and coarse phase separation, it is found that the inferior performance of the latter devices is, at least partially, due to poor electron transport.
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| 5. |
- van Reenen, Stephan, et al.
(författare)
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Origin of Work Function Modification by Ionic and Amine-Based Interface Layers
- 2014
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Ingår i: Advanced Materials Interfaces. - : Wiley-VCH Verlagsgesellschaft. - 2196-7350. ; 1:8, s. 1400189-
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Tidskriftsartikel (refereegranskat)abstract
- Work function modification by polyelectrolytes and tertiary aliphatic amines is found to be due to the formation of a net dipole at the electrode interface, induced by interaction with its own image dipole in the electrode. In polyelectrolytes differences in size and side groups between the moving ions lead to differences in approach distance towards the surface. These differences determine magnitude and direction of the resulting dipole. In tertiary aliphatic amines the lone pairs of electrons are anticipated to shift towards their image when close to the interface rather than the nitrogen nuclei, which are sterically hindered by the alkyl side chains. Data supporting this model is from scanning Kelvin probe microscopy, used to determine the work function modification by thin layers of such materials on different substrates. Both reductions and increases in work function by different materials are found to follow a general mechanism. Work function modification is found to only take place when the work function modification layer (WML) is deposited on conductors or semiconductors. On insulators no effect is observed. Additionally, the work function modification is independent of the WML thickness or the substrate work function in the range of 3 to 5 eV. Based on these results charge transfer, doping, and spontaneous dipole orientation are excluded as possible mechanisms. This understanding of the work function modification by polyelectrolytes and amines facilitates design of new air-stable and solution-processable WMLs for organic electronics.
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