In the blue light-emitting polymer poly(9,9-dioctylfluorene) (PFO) two distinct morphological phases have been identified, that is the glassy phase and a planar ß-phase. We show that the proportion of the formation of the two phases can be controlled by simply spinning thin films from different solvents such as chloroform and cyclopentanone. We use a Franck–Condon analysis with vibrational modes obtained from Raman spectra to analyze the emission spectra at low temperature. Films spun from cyclopentanone are dominated by from the ß-phase emission while films spun from chloroform have a high fraction of glassy phase emission. Comparison between absorption and emission spectra shows evidence for spectral diffusion from the glassy to the ß-phase. We discuss the Huang–Rhys parameters for both phases.