| 1. |
- Bjoerstroem, Cecilia M., et al.
(author)
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Influence of solvents and substrates on the morphology and the performance of low-bandgap polyfluorene: PCBM photovoltaic devices
- 2006
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In: Proceedings of SPIE-The International Society for Optical Engineering. ; 6192, s. 61921X/1-
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Conference paper (peer-reviewed)abstract
- Spin-coated thin films of poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (APFO-3) blended with [6,6]-phenyl-C61-butyric acid Me ester (PCBM) are used as the active material in polymer photovoltaic cells. Such blends are known for their tendency to phase sep. during film formation. Tuning the morphol. of the blend in a controlled way is one possible road towards higher efficiency. We studied the effect of adding chlorobenzene to chloroform-based blend solns. before spin-coating on the conversion efficiency of APFO-3:PCBM photodiodes, and related that to the lateral and vertical morphol. of thin films of the blend. The lateral morphol. is imaged by at. force microscopy (AFM) and the vertical compositional profile is obtained by dynamic secondary ion mass spectrometry (SIMS). The profiles reveal compositional variations consisting of multilayers of alternating polymer-rich and PCBM-rich domains in the blend film spin-coated from chloroform. The vertical compositional variations are caused by surface-directed spinodal waves and are frozen in during the rapid evapn. of a highly volatile solvent. With addn. of the low-vapor pressure solvent chlorobenzene, a more homogeneous vertical compn. is found. The conversion efficiency for solar cells of this blend was found to be optimal for chloroform:chlorobenzene mixts. with a vol.-ratio of 80:1. We have also investigated the role of the substrate on the morphol. We found that blend films spin-coated from chloroform solns. on PEDOT:PSS-coated ITO show a similar compositional structure as the films on silicon, and that changing the substrate from silicon to gold only affects the vertical phase sepn. in a region close to the substrate interface. [on SciFinder (R)]
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| 2. |
- Bjoerstroem, Cecilia M., et al.
(author)
-
Multilayer formation in spin-coated thin films of low-bandgap polyfluorene: PCBM blends
- 2005
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In: Journal of Physics: Condensed Matter. ; 17:50, s. L529-L534
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Journal article (peer-reviewed)abstract
- Blends of the low-bandgap polymer poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-5,5-(4',7'-di-2-thienyl- 2',1',3'-benzothiadiazole)] (APFO-3) and the fullerene deriv. [6,6]-phenyl-C61-butyric acid Me ester (PCBM) were spin-coated from chloroform soln. into thin films, which were examd. with dynamic secondary ion mass spectrometry. For blends with high PCBM content, the depth profiles show compn. waves that were caused by surface-directed phase sepn. during spin-coating. The formation of such multilayer structures by spontaneous self-stratification probably has implications for optimization strategies for the performance of org. solar cells. [on SciFinder (R)]
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| 3. |
- Bjorstrom, Cecilia M., et al.
(author)
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Influence of solvents and substrates on the morphology and the performance of low-bandgap polyfluorene: PCBM photovoltaic devices - art. no. 61921X
- 2006
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In: Proceedings of SPIE, the International Society for Optical Engineering. - : International Society for Optical Engineering; 1999. - 0277-786X .- 1996-756X. ; 6192, s. X1921-X1921
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Journal article (peer-reviewed)abstract
- Spin-coated thin films of poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-5,5-(4,7-di-2-thienyl-2,1,3-benzothiadiazole)] (APFO-3) blended with [6,6]-phenyl-C-61-butyric acid methyl ester (PCBM) are used as the active material in polymer photovoltaic cells. Such blends are known for their tendency to phase separate during film formation. Tuning the morphology of the blend in a controlled way is one possible road towards higher efficiency. We studied the effect of adding chlorobenzene to chloroform-based blend solutions before spin-coating on the conversion efficiency of APFO-3:PCBM photodiodes, and related that to the lateral and vertical morphology of thin films of the blend. The lateral morphology is imaged by atomic force microscopy (AFM) and the vertical compositional profile is obtained by dynamic secondary ion mass spectrometry (SIMS). The profiles reveal compositional variations consisting of multilayers of alternating polymer-rich and PCBM-rich domains in the blend film spin-coated from chloroform. The vertical compositional variations are caused by surface-directed spinodal waves and are frozen in during the rapid evaporation of a highly volatile solvent. With addition of the low-vapour pressure solvent chlorobenzene, a more homogeneous vertical composition is found. The conversion efficiency for solar cells of this blend was found to be optimal for chloroform: chlorobenzene mixtures with a volume-ratio of 80:1. We have also investigated the role of the substrate on the morphology. We found that blend films spin-coated from chloroform solutions on PEDOT:PSS-coated ITO show a similar compositional structure as the films on silicon, and that changing the substrate from silicon to gold only affects the vertical phase separation in a region close to the substrate interface.
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| 4. |
- Bjorstrom, C. M., et al.
(author)
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Vertical phase separation in spin-coated films of a low bandgap polyfluorene/PCBM blend - Effects of specific substrate interaction
- 2007
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In: Applied Surface Science. - Amsterdam : Elsevier BV. - 0169-4332 .- 1873-5584. ; 253:8, s. 3906-3912
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Journal article (peer-reviewed)abstract
- We report on the effect of the substrate on the vertical phase separation in spin-coated thin films of poly [(9,9-dioctylfluorenyl-2,7-diyl)-co-5,5-4',7'-di-2-thienyl-2',1',3'-benz othiadiazole] (APFO-3) blended with [6,6]-phenyl-C-61-butyric acid methyl ester (PCBM). Compositional depth profiles of the films are measured by dynamic secondary ion mass spectrometry (SIMS). We found that changing the substrate from silicon to gold affects the composition profile near the substrate interface. This is caused by a specific interaction between the polymer (APFO-3) and the gold surface, as confirmed by X-ray photoelectron spectroscopy (XPS). The composition profile in the area away from the substrate interface, as well as the enrichment of the free surface with APFO-3, remain however unaffected by the choice of substrate. The vertical composition was also analysed for APFO-3:PCBM films spin-coated on indium tin oxide (ITO) coated with a thin layer of (3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS). (c) 2006 Elsevier B.V. All rights reserved.
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| 5. |
- Björström, Cecilia M., et al.
(author)
-
Influence of solvents and substrates on the morphology and the performance of low-bandgap polyfluorene:PCBM photovoltaic devices
- 2006
-
In: Proceedings of SPIE, the International Society for Optical Engineering. - Cardiff : SPIE - International Society for Optical Engineering. - 0277-786X .- 1996-756X. ; 6192, s. 61921X-
-
Journal article (peer-reviewed)abstract
- Spin-coated thin films of poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (APFO-3) blended with [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) are used as the active material in polymer photovoltaic cells. Such blends are known for their tendency to phase separate during film formation. Tuning the morphology of the blend in a controlled way is one possible road towards higher efficiency. We studied the effect of adding chlorobenzene to chloroform-based blend solutions before spin-coating on the conversion efficiency of APFO-3:PCBM photodiodes, and related that to the lateral and vertical morphology of thin films of the blend. The lateral morphology is imaged by atomic force microscopy (AFM) and the vertical compositional profile is obtained by dynamic secondary ion mass spectrometry (SIMS). The profiles reveal compositional variations consisting of multilayers of alternating polymer-rich and PCBM-rich domains in the blend film spin-coated from chloroform. The vertical compositional variations are caused by surface-directed spinodal waves and are frozen in during the rapid evaporation of a highly volatile solvent. With addition of the low-vapour pressure solvent chlorobenzene, a more homogeneous vertical composition is found. The conversion efficiency for solar cells of this blend was found to be optimal for chloroform:chlorobenzene mixtures with a volume-ratio of 80:1. We have also investigated the role of the substrate on the morphology. We found that blend films spin-coated from chloroform solutions on PEDOT:PSS-coated ITO show a similar compositional structure as the films on silicon, and that changing the substrate from silicon to gold only affects the vertical phase separation in a region close to the substrate interface
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| 6. |
- Björström, Cecilia M., et al.
(author)
-
Multilayer formation in spin-coated thin films of low-bandgap polyfluorene:PCBM blends
- 2005
-
In: Journal of Physics. - Philadelphia : Institute of Physics Publishing (IOPP). - 0953-8984 .- 1361-648X. ; 17:50, s. L529-L534
-
Journal article (peer-reviewed)abstract
- Blends of the low-bandgap polymer poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-5,5- (4',7'-di-2-thienyl-2',1',3'-benzothiadiazole] (APFO-3) and the fullerene derivative [6,6]-phenyl–C61–butyric acid methyl ester (PCBM) were spin-coated from chloroform solution into thin films, which were examined with dynamic secondary ion mass spectrometry. For blends with high PCBM content, the depth profiles show composition waves that were caused by surface-directed phase separation during spin-coating. The formation of such multilayer structures by spontaneous self-stratification is likely to have implications for optimization strategies for the performance of organic solar cells
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| 7. |
- Budkowski, Andrzej, et al.
(author)
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Structures in multi-component polymer films : their formation, observation and applications in electronics and biotechnology
- 2009
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In: Acta Physica Polonica. A. - Warsaw : Polish Academy of Sciences, Institute of Physics. - 0587-4246 .- 1898-794X. ; 115:2, s. 435-440
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Journal article (peer-reviewed)abstract
- Several strategies to form multicomponent films of functional polymers, with micron, submicron and nanometer structures, intended for plastic electronics and biotechnology are presented. These approaches are based on film deposition from polymer solution onto a rotating substrate (spin-casting), a method implemented already on manufacturing lines. Film structures are determined with compositional (nanometer) depth profiling and (submicron) imaging modes of dynamic secondary ion mass spectrometry, near-field scanning optical microscopy (with submicron resolution) and scanning probe microscopy (revealing nanometer features). Self-organization of spin-cast polymer mixtures is discussed in detail, since it o®ers a one-step process to deposit and align simultaneously domains, rich in di®erent polymers, forming various device elements: (i) Surface segregation drives self-stratification of nanometer lamellae for solar cells and anisotropic conductors. (ii) Cohesion energy density controls morphological transition from lamellar (optimal for encapsulated transistors) to lateral structures (suggested for light emitting diodes with variable color). (iii) Selective adhesion to substrate microtemplates, patterned chemically, orders lateral structures for plastic circuitries. (iv) Submicron imprints of water droplets (breath figures) decorate selectively micron-sized domains, and can be used in devices with hierarchic structure. In addition, selective protein adsorption to regular polymer micropatterns, formed with soft lithography after spin-casting, suggests applications in protein chip technology. An approach to reduce lateral blend film structures to submicron scale is also presented, based on (annealed) films of multicomponent nanoparticles
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| 8. |
- Jaczewska, Justyna, et al.
(author)
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Ordering domains of spin cast blends of conjugated and dielectric polymers on surfaces patterned by soft- and photo-lithography
- 2009
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In: Soft Matter. - London : Royal Society of Chemistry. - 1744-683X. ; 5:1, s. 234-241
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Journal article (peer-reviewed)abstract
- Spin casting polymer blends of conjugated and dielectric macromolecules onto chemically patterned metal and oxidized silicon surfaces might provide a simple method to fabricate polymer-based circuitries that can be integrated with conventional electronics. Such solution-processing of the blend components offers simultaneous deposition and pattern-directed alignment of the phase separated polymer domains. The alignment is driven by self-organization guided by preferential surface segregation. Here we demonstrate that the laterally arranged domain structures in spin cast films of theconjugated poly(3-alkylthiophenes) (P3ATs): P3BT, P3DDT and regioregular R-P3HT, blended with dielectric polystyrene (PS), can be ordered by three different surface templates. The templates are formed by a patterned self-assembled monolayer (SAM), micro-contact printed on the surface of interest, i.e. hexadecanethiols on gold (for alignment of P3DDT/PS blend) and octadecyltrichlorosilanes on oxidized silicon (for R-P3HT/PS). Additionally gold lines are micropatterned on SiO2 with photo-lithography (for P3BT/PS mixture). The forces driving pattern-directed self-organization of the polymers are discussed based on complementary studies of preferential surface segregation, observed for blend films spin cast on homogeneous surfaces that correspond to the different regions of the surface templates
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| 9. |
- Jaczewska, Justyna, et al.
(author)
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Polymer vs Solvent Diagram of Film Structures Formed in Spin-Cast Poly(3-alkylthiophene) Blends
- 2008
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In: Macromolecules. - Washington : American Chemical Society. - 0024-9297 .- 1520-5835. ; 41, s. 4802-4810
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Journal article (peer-reviewed)abstract
- A polymer vs solvent diagram of film structures, formed in polystyrene (PS) blends (1:1 w:w PS/PT) with poly(3-alkylthiophenes) PT [regioregular R-P3DDT, R-P3HT and regiorandom P3BT, P3DDT] spincoated onto oxidized silicon surfaces from various common solvents [p-xylene, toluene, chloroform, chlorobenzene, cyclohexanone] is presented. The structures were determined with microscopic techniques (atomic, AFM and lateral, LFM, force microscopy, fluorescent microscopy FM) and dynamic secondary ion mass spectrometry (dSIMS). The diagram, arranged according to the solubility parameter of the PTs and the solvents, exhibits three main structural classes: dewetting, lamellar, and lateral (quasi-2-dim) morphology. Decrease in PT solubility parameter δPT inhibits dewetting of polymer films. It induces also a transition from lamellar to lateral film structure. Increase in solvent solubility parameter δS has similar effects. Such behavior is related to the stability of transient homogeneous films and multilayers in the course of spin-casting. The role of δPT and δS is elucidated based on the stability analysis performed in terms of spreading coefficient (dependent on δPT) and effective interfacial tension of solvent-rich polymer phase (dependent on δS).
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| 10. |
- Nilsson, Svante, et al.
(author)
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Morphology and phase segregation of spin-casted films of polyfluorene/PCBM blends
- 2007
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In: Macromolecules. - ACS : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 40:23, s. 8291-8301
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Journal article (peer-reviewed)abstract
- In this study the morphology of spin-casted films of polymers blended with [6,6]-phenyl C61-butyric acid methyl ester (PCBM) has been studied. It was found that the lateral structure formation in the films is favored by rapid solvent evaporation and strong polymer−PCBM repulsion. The formation of homogeneous films is favored by slow evaporation and weak polymer−PCBM repulsion. The effect of solvent evaporation rate is the opposite of what is found for spin-casting polymer−polymer blends. The results can be explained by the kinetics of phase separation and the phase behavior involving limited solubility and crystallization of PCBM.
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