Hydrostatic pressure dependence of the luminescence and Raman frequencies in polyfluorene

TL;DR

This study investigates how hydrostatic pressure affects the luminescence and vibrational properties of polyfluorene, revealing significant changes in photoluminescence and Raman spectra at specific pressure thresholds.

Contribution

It provides new insights into pressure-induced electronic and vibrational behavior of polyfluorene, highlighting the interplay between aggregation, defects, and electron-phonon interactions.

Findings

PL and vibronic features change dramatically around 20-35 kbar.

Raman peaks shift to higher energies and show antiresonance lineshapes.

Pressure influences aggregation and defect-related emission in polyfluorene.

Abstract

We present studies of the photoluminescence (PL), absorption and Raman scattering from poly[2,7-(9,9'-bis(2-ethylhexyl))fluorene] 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 lineshapes at higher pressures, indicating a strong electron-phonon interaction.