A Study on the Film Morphology and Photophysics of Polyfluorene

We have studied the interplay between photophysics and film morphology in poly(9.9-dioctyl fluorene) using a variety of optical probes, including absorption, photoluminescence, and photoinduced absorption. Upon slowly warming a glassy PFO film from 80K to 300K, a fraction of the sample is transformed into a new solid phase, the beta phase. The beta phase has more extended conjugation than the glassy phase. As a consequence, the beta phase excitons are red-shifted and dissociate more easily into long-lived ed charged polarons.