Polarized Emissions from Single Crystals of Thiophene/Phenylene Co-Oligomers Measured by Microspectroscopy

Polarized emissions have been investigated for single crystals of thiophene/phenylene co-oligomers by microspectroscopic measurements. We measured polarized emissions from two distinct parts on the single-crystal surface (the a b -plane) that were produced by the polarized UV excitation light. At the defect-free part of the crystals, the largest emissions are observed at both the excitation and the emission polarization directions along the crystal short axis on the a b -plane. At the crystal edge, on the other hand, the emissions are strongly polarized along another axis (that is normal to the crystal short axis). For the latter feature, the reflected emission at the crystal edge plays an important role.