Single molecule spectroscopy of polyfluorenes

Abstract

Single molecule spectroscopy resolves some of the crucial issues in the photophysics of polyfluorenes. After an introduction on single molecule spectroscopy we present the ability of this technique in revealing the intramolecular nature of the photophysical phenomena encountered in the different phases of polyfluorene and in fluorenone-fluorene copolymers. First, we correlate the peculiar emission properties of the phases to their chain extension, probed by using polarisation sensitive studies. Moreover, by looking at single chromophores in the β phase, we demonstrate how a slight bending in this one-dimensional structure does not disrupt the π conjugation while impacting on the exciton linewidth, a crucial parameter for the comprehension of energy and charge transfer. As a definitive answer to the colour degradation, we report the single chain spectroscopy of fluorenone-fluorene copolymers, demonstrating the monomolecular origin of the green emission. More generally, the presented experiments illustrate the unique possibilities offered by single molecule spectroscopy in correlating the structure and the resulting electronic properties in conjugated polymers. © Springer-Verlag.