Resist-free laser patterning of perfluoro-alkyl functionalized fullerene films: Attaining pattern and stability by order

We report that it is possible to establish well-defined semiconducting patterns in a perfluoro-alkyl functionalized fullerene (C60-F) film using a straightforward, benign and scalable method. The patterning technique comprises a direct laser light exposure of pre-select film areas, and a subsequent development in a heptane developer solution that selectively removes the non-exposed areas of the film. It is notable that no sacrificial photo-resist material is utilized, and that the remaining patterned C60-F material exhibits high electron mobility (>4 × 10−2 cm2/Vs, as quantified in transistor experiments) and improved ambient stability, both in comparison to the pristine material and to the more commonly utilized fullerene PCBM. We demonstrate that the patterning process has left the remaining C60-F material chemically unaltered, but that its degree of crystallinity has increased. The latter rationalizes the high electron mobility, the improved air stability, and the decreased solubility in the developer solution.