Pressure effect on photoluminescence and Raman spectra of PPV

The pressure effect on photoluminescence (PL) and Raman spectra of the poly (para-phenylene vinylene) (PPV) has been investigated with a diamond anvil cell (DAC) under the hydrostatic pressure condition. The intensity ratios, I1167/I1622 and I1543/I1622, increase with pressure. This indicates that the conjugated length of PPV is enhanced at high pressures. In addition, appearance of a new Raman band corresponding to CC stretch at 1190 cm−1 shows that the chain conformation defects decreased with increasing pressure. The redshift of the PL spectra and shift to higher frequencies for Raman bands with increase in pressure are explained by combining the conjugation model with amplitude mode model.