X-ray diffraction studies of the structure and orientations of thiophene and fluorenone based molecule

The crystal structure of a conjugated molecule containing thiophene and fluorenone residues has been determined from powder X-ray diffraction (XRD). Thin films (<40 nm thick) of this molecule, grown in high vacuum (10-5 Pa) onto oxidized silicon substrates, are oriented along with different crystallographic directions. A comparison of XRD in both Grazing Incidence and Bragg–Brentano geometries allowed to perform a quantitative analysis of the various orientations. This approach is generally applicable in the case of multi-oriented films. The results fully account for the poor performance of this molecule in p-type field effect transistor devices.