Hydrostatic pressure dependence of the luminescence and Raman frequencies in polyfluorene

We present studies of the photoluminescence (PL), absorption, and Raman scattering spectra from $\mathrm{poly}[2,7-({9,9}^{\prime }-\mathrm{bis}(2\mathrm{}-\mathrm{ethylhexyl})\left)\mathrm{fluorene}\right]$ under hydrostatic pressures of 0–100 kbar at room temperature. The well-defined PL and associated vibronics that are observed at atmospheric pressure change dramatically around 20 kbar in the bulk sample and at around 35 kbar for the thin-film sample. Beyond these pressures the PL emission from the backbone is swamped by strong peaks due to aggregates and keto defects in the 2.1–2.6 eV region. The Raman peaks shift to higher energies and exhibit unexpected antiresonance line shapes at higher pressures, indicating a strong electron-phonon interaction.