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Surface induced orientation and vertically layered morphology in thin films of poly(3-hexylthiophene) crystallized from the melt

Published online by Cambridge University Press:  11 April 2017

Jens Balko ,
Guiseppe Portale ,
Ruth H. Lohwasser ,
Mukundan Thelakkat  and
Thomas Thurn-Albrecht Open the ORCID record for Thomas Thurn-Albrecht [Opens in a new window]
Jens Balko
Affiliation:
Institute of Physics, Martin Luther University, 06120 Halle/Saale, Germany
Guiseppe Portale
Affiliation:
Zernike Institute for Adv. Materials, University of Groningen, NL-9747 AG Groningen, The Netherlands
Ruth H. Lohwasser
Affiliation:
Applied Functional Materials, Macromolecular Chemistry I, University of Bayreuth, 95440 Bayreuth, Germany
Mukundan Thelakkat
Affiliation:
Applied Functional Materials, Macromolecular Chemistry I, University of Bayreuth, 95440 Bayreuth, Germany
Thomas Thurn-Albrecht*
Affiliation:
Institute of Physics, Martin Luther University, 06120 Halle/Saale, Germany
*
a) Address all correspondence to this author. e-mail: thomas.thurn-albrecht@physik.uni-halle.de
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Abstract

The presence of interfaces and geometrical confinement can have a strong influence on the structure and morphology of thin films of semicrystalline polymers. Using surface-sensitive grazing incidence wide angle X-ray scattering and atomic force microscopy to investigate the vertical structure of thin films of poly(3-hexylthiophene) crystallized from the melt, we show that highly oriented crystallites are induced at the air/polymer interface and not as sometimes assumed at the interface to the substrate. These crystallites are oriented with their crystallographic a-axis perpendicular to the plane of the film. While the corresponding orientation dominates in thinner films, for sufficiently thick films (>60 nm) a layer containing unoriented crystals is present below the surface layer. Due to the anisotropic charge transport properties, the observed effects are expected to be of special relevance for potential applications of semiconductor polymers in the field of organic photovoltaics for which vertical transport in thicker films plays an important role.

Keywords

polymernanostructuresemiconducting
Type
Invited Articles
Information
Journal of Materials Research , Volume 32 , Issue 10: Focus Issue: Microstructural Characterization for Emerging Photovoltaic Materials , 26 May 2017 , pp. 1957 - 1968
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Copyright
Copyright © Materials Research Society 2017 

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Footnotes

b)

Present Address: Fraunhofer Institute for Applied Polymer Research, 14476 Potsdam, Germany

c)

Present Address: BASF, Ludwigshafen, Germany

Contributing Editor: Chris Nicklin

References

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