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Molecular Orientation and Composition at the Surface of Spin-Coated Polyfluorene:Fullerene Blend Films
Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. (Materialfysik)
Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik. (Materialvetenskap)
Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik. (Materialfysik)ORCID-id: 0000-0003-1711-5595
Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik. (Materialvetenskap)ORCID-id: 0000-0002-1609-8909
2013 (Engelska)Ingår i: Journal of Polymer Science Part B: Polymer Physics, ISSN 0887-6266, E-ISSN 1099-0488, Vol. 51, nr 3, s. 176-182Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The surface composition in spin-coated films of polyfluorene:fullerene blends was determined quantitatively by near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. By comparing partial and total electron yield spectra, we found vertical compositional differences in the surface region. Furthermore, the orientation of the polymer chains was investigated by variable-angle NEXAFS. Blend films of poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole] with [6,6]-phenyl-C61-butyric acid methyl ester in two different blend ratios were studied. Results showed polymer enrichment of the surfaces for films with a polymer:fullerene weight ratio of 20:80 and of 50:50, spin-coated from both chlorobenzene and chloroform solutions. The angular dependence of the NEXAFS spectra of the pure polymer films showed a preferential plane-on orientation, which was slightly stronger in the subsurface region than at the surface. In blend films, this orientational preference was less pronounced and the difference between surface and subsurface vanished

Ort, förlag, år, upplaga, sidor
Hoboken, New Jersey: John Wiley & Sons, 2013. Vol. 51, nr 3, s. 176-182
Nyckelord [en]
polymer solar cell, bulk heterojunction, phase separation, morphology, miscibility, near-edge X-ray absorption fine structure
Nationell ämneskategori
Fysik
Forskningsämne
Fysik
Identifikatorer
URN: urn:nbn:se:kau:diva-16005DOI: 10.1002/polb.23198ISI: 000312728600002OAI: oai:DiVA.org:kau-16005DiVA, id: diva2:573259
Tillgänglig från: 2012-11-30 Skapad: 2012-11-30 Senast uppdaterad: 2019-05-20Bibliografiskt granskad
Ingår i avhandling
1. Materials aspects in spin-coated films for polymer photovoltaics
Öppna denna publikation i ny flik eller fönster >>Materials aspects in spin-coated films for polymer photovoltaics
2013 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Polymer-based photovoltaics have the potential to contribute to boosting photovoltaic energy conversion overall. Besides allowing large-area inexpensive processing, polymeric materials have the added benefit of opening new market applications for photovoltaics due to their low-weight and interesting mechanical properties. The energy conversion efficiency values of polymer photovoltaics have reached new record values over the past years. It is however crucial that stability issues are addressed together with efficiency optimization. Understanding fundamental materials aspects is key in both areas.

In the work presented in this thesis, the morphology of polymer:fullerene films and its influence on device performance was studied, as well as the effect of light exposure on the surface of fullerene films. Several polyfluorene copolymers were used for the morphology studies, where the effects of changing spin-coating solvent and of side chain engineering were investigated with dynamic secondary ion mass spectrometry (dSIMS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. Polymer-enriched surfaces were found in all blend films, even in the cases with homogeneous distributions in the bulk. Side chain engineering of the polymer led to gradual changes in the compositional variations perpendicular to the surface, and to slight variations in the photocurrent. The electronic structure of the fullerene derivative PCBM was studied in detail and the spectroscopic fingerprint of the materials was analysed by comparison with theoretically simulated spectra. Photo-stability studies done in air showed that the surface of fullerene films underwent severe damages at the molecular level, which is evident from changes in the valence band and X-ray absorption spectra. These changes were explained by transitions from sp2-type to sp3 hybridization of the carbon atoms in the cage that resulted in the destruction of the fullerene cage.

Ort, förlag, år, upplaga, sidor
Karlstad: Karlstads universitet, 2013. s. 88
Serie
Karlstad University Studies, ISSN 1403-8099 ; 2013:3
Nyckelord
materials science, photovoltaics, conjugated polymer, polymer solar cell, bulk heterojunction, coating, morphology, fullerene, photostability, degradation, X-ray absorption spectroscopy, synchroton-based techniques
Nationell ämneskategori
Fysik
Forskningsämne
Materialvetenskap
Identifikatorer
urn:nbn:se:kau:diva-16107 (URN)978-91-7063-475-8 (ISBN)
Disputation
2013-01-25, 21A342, Karlstad University, SE-651 88, Karlstad, 13:15 (Engelska)
Opponent
Handledare
Tillgänglig från: 2013-01-07 Skapad: 2012-12-07 Senast uppdaterad: 2013-01-07Bibliografiskt granskad

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Förlagets fulltexthttp://onlinelibrary.wiley.com/doi/10.1002/polb.23198/abstract;jsessionid=754B2451F465DAC03AF3D8D10A420707.d04t02

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Anselmo, Ana SofiaDzwilewski, AndrzejSvensson, KristerMoons, Ellen

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