Phenyl-capped oligothiophenes: novel light-emitting materials with different molecular alignments in thin films

We have developed novel light-emitting materials consisting of phenyl-capped oligothiophenes and studied their spectroscopic and structural characteristics in the thin film form. These oligothiophenes have one to four thiophene unit(s) in the molecule. Emission maxima for these materials cover the spectral range 470 to 620 nm and blue to orange emissions are clearly visible. On the basis of the X-ray diffraction studies, we show that the thin films exhibit different molecular alignment (either vertical or parallel) depending on the compounds, even though those films were prepared under the same condition. This is consistent with the results of the absorption spectroscopy.