Growth, Structure, and Anisotropic Optical Properties of Difluoro-anthradithiophene Thin Films

Anthradithiophene (ADT) and its functionalized derivatives have proven to be attractive for high-performance electronic devices based on small-molecule organic semiconductors. In this manuscript we investigate the structural and optical properties of thin films of difluoro-anthradithiophene (diF-ADT), an ADT derivative, grown by organic molecular beam deposition (OMBD). By grazing incidence X-ray diffraction and reciprocal space maps, we show that diF-ADT crystallizes in a thin film structure similar to the single crystal unit cell. In addition, we investigate the growth characteristics with atomic force microscopy (AFM) and show an increase of surface mound sizes with elevated substrate temperature. Optical absorption measurements reveal a clear vibronic progression in both solution and thin film spectra along with a distinct optical anisotropy related to the molecular orientation in thin films.