Single molecule spectroscopy of poly 3-octyl-thiophene (P3OT).

We report on the spectroscopy of isolated chains of P3OT, in a highly dilute solution in the inert polymer host poly(methyl-methacrylate) (PMMA). This environment permits a detailed analysis of emission transitions in the 1.9-2.2 eV range by suppressing the formation of the lowest emitting-energy aggregated form of P3OT. Herein it is observed that the 1.9-2.2 eV band is in fact split into low (red) and high (blue) energy forms in a highly analogous situation to that found for the conjugated polymer MEH-PPV. Another focus of this work is an investigation of the interaction of singlet and triplet excitons in P3OT. The results indicate that, like in MEH-PPV, triplet excitons are highly efficient fluorescence quenchers for P3OT, strongly quenching the fluorescence of P3OT under even relatively low excitation intensities.