TU/e Soft Matter CryoTEM Research Unit

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Polymer Films

Thin Films

Figure 1: Outcome of electron tomography applied to the PF10TBT/PCBM films (with high molecular weight PF10TBT-polymer[1].

Electron tomographic methods were developed to study the three-dimensional nanoscale organization in the photoactive layers of polymer solar cells[1]. This allowed us to directly observe for the first time and with nanometer resolution, morphologies that were previously suggested based on other experiments[2-4]. The observed morphologies could be related to the performance of solar cell devices and will be of great importance for their future development[5]. Moreover, electron tomography was used to reveal the relation between processing conditions, the resulting morphology and the performance of the photoactive layers[6].

Thick Films

High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) was used to investigate two component carbon-based polymer systems. The density of the different phases generated a high contrast in HAADF-STEM, allowing the imaging of the interface organization and assignment of the different phases and demonstrating the power of HAADF-STEM as an imaging technique for polymer systems (Figure 2)[7-8]. Moreover, it was demonstrated that low convergent angle HAADF-STEM can be used to image ultra thick (multi-micrometer) polymer films with nanometer resolution[9]. In collaboration with the group of prof. C. E. Koning (TU/e) the structure of carbon nanotube based composites were investigated in a series of studies[10-14].

Figure 2: TEM images of a thermoplastic vulcanized (TPV) specimen imaged in different modes: bright field conventional TEM of (A) unstained specimens; (B) high-angle annular dark field scanning TEM image of the same area as imaged in A (arrows indicate same specimen features)[7].

References

1. S. van Bavel, E.D. Sourty, G. de With, J. Loos, Three-dimensional nanoscale organisation of polymer solar cells, Journal of Materials Chemistry 19 [30](2009) 5388-5393.
2. J. Loos, R.A.J. Janssen, Compositional and electric field dependence of the dissociation of charge transfer excitons in alternating polyfluorene copolymer/fullerene blends, J. American Chemical Society 130 [24] (2008) 7721-7735.
3. S. van Bavel, E.D. Sourty, G. de With, J. Loos, Three-dimensional nanoscale organisation of bulk heterojunction polymer solar cells, Nano Letters 9 [2] (2009) 507-513.
4. S.D. Oosterhout,M.M. Wienk, S.S. van Bavel, R. Thiedmann, L.J.A. Koster,J. Gilot, J. Loos, V. Schmidt, R.A.J. Janssen, The effect of three-dimensional morphology on the efficiency of hybrid polymer solar cells, Nature Materials, 8(10) (2009) 818-824.
5. K. Maturovà, S.S. van Bavel, M.M. Wienk, R.A.J. Janssen and M. Kemerink, Morphological Device Model for Organic Bulk Heterojunction Solar Cells, Nano Letters 9 [8] (2009) 3032-3037.
6. W. Grzegorczyk, G. Palaniswamy, T. Savenije, S. van Bavel, J. Loos, E. Sudhölter, L. Siebbeles, H. Zuilhof, Photoconductance of bulk heterojunctions with tunable nanomorphology consisting of P3HT and naphthalene diimide siloxane oligomers, The Journal of Physical Chemistry C 113 (2009) 7863-7869.
7. E. Sourty, S. van Bavel, K. Lu, R. Guerra, G. Bar, J. Loos, High-Angle Annular Dark Field (HAADF) Scanning Transmission Electron Microscopy (STEM) on carbon-based functional polymer systems, Microscopy and Microanalysis 15 (2009) 251-258.
8. J.Loos, E. Sourty, K. Lu, G. de With, S.S. van Bavel, Imaging polymer systems with High-Angle Annular Dark Field Scanning Transmission Electron Microscopy (HAADF-STEM), Macromolecules 42 (2009) 2581-2586.
9. E. Sourty, B. Freitag, D. Wall, D. Tang, K. Lu, J. Loos, Tomographic imaging ultra-thick specimens with nanometer resolution, Microscopy and Microanalysis 14 Suppl 2 (2008) 1056-1057.
10. K. Lu, N. Grossiord, C.E. Koning, H.E. Mitler, B. van Mele, J. Loos, Carbon nanotube (CNT) / Isotactic polypropylene composites prepared by latex technology: Morphology analysis of CNT-induced nucleation, Macromolecules 41 [21] (2008) 8081-8085.
11. J. Yu, K. Lu, E. Sourty, N. Grossiord, C.E. Koning, J. Loos, Characterization of conductive multiwall carbon nanotube/polystyrene composites prepared by latex technolgy, Carbon 45 (2007) 2897-2903.
12. N. Grossiord, J. Loos, J. Meuldijk, O. Regev, H.E. Miltner, B. van Mele, C.E. Koning, Conductive carbon-nanotube/polymer composites: Spectroscopic monitoring of the exfolation process in water, Composites Science and Technology 67 (2007) 778-782.
13. N. Grossiord, H.E. Mitler, J. Loos, J. Meuldijk, B. van Mele, C.E. Koning, On the crucial role of wetting in the preparation of conductive polystyrene-carbon nanotube composites, Chemistry of Materials 19 (2007) 3787-3792.
14. J. Loos, N. Grossiord, C.E. Koning, O. Regev,On the fate of carbon nanotubes: Morphological characterisations, Composites Science and Technology 67 (2007) 783-788.