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Nanomorphology of P3HT:PCBM-Based Absorber Layers of Organic Solar Cells after Different Processing Conditions Analyzed by Low-Energy Scanning Transmission Electron Microscopy

  • Marina Pfaff (a1) (a2), Michael F.G. Klein (a3), Erich Müller (a1) (a2), Philipp Müller (a1) (a2), Alexander Colsmann (a3), Uli Lemmer (a2) (a3) and Dagmar Gerthsen (a1) (a2)...

Abstract

In this study the nanomorphology of P3HT:PC61BM absorber layers of organic solar cells was studied as a function of the processing parameters and for P3HT with different molecular weight. For this purpose we apply scanning transmission electron microscopy (STEM) at low electron energies in a scanning electron microscope. This method exhibits sensitive material contrast in the high-angle annular dark-field (HAADF) mode, which is well suited to distinguish materials with similar densities and mean atomic numbers. The images taken with low-energy HAADF STEM are compared with conventional transmission electron microscopy and atomic force microscopy images to illustrate the capabilities of the different techniques. For the interpretation of the low-energy HAADF STEM images, a semiempirical equation is used to calculate the image intensities. The experiments show that the nanomorphology of the P3HT:PC61BM blends depends strongly on the molecular weight of the P3HT. Low-molecular-weight P3HT forms rod-like domains during annealing. In contrast, only small globular features are visible in samples containing high-molecular-weight P3HT, which do not change significantly after annealing at 150°C up to 30 min.

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Corresponding author

* Corresponding author. E-mail: marina.pfaff@kit.edu

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Keywords

Nanomorphology of P3HT:PCBM-Based Absorber Layers of Organic Solar Cells after Different Processing Conditions Analyzed by Low-Energy Scanning Transmission Electron Microscopy

  • Marina Pfaff (a1) (a2), Michael F.G. Klein (a3), Erich Müller (a1) (a2), Philipp Müller (a1) (a2), Alexander Colsmann (a3), Uli Lemmer (a2) (a3) and Dagmar Gerthsen (a1) (a2)...

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