Site-selective luminescence spectroscopy (SSL) was employed to resolve the vibracional modes in self-assembled poly(p-phenylene vinylene), PPV. Using Franck-Condon analysis, the PPV spectra can be well described by three effective vibrational modes at 330, 1160 and 1550 cm-1. As the temperature increases from 4 to 180 K the electron-phonon coupling (S factor) remains constant for the 1550 cm-1 mode while for other lower energy modes the coupling increases monotonically. This trend is consistent with the decrease of the conjugation length due to the increase of thermal disorder. We find that the temperature dependence of vibrational progression in PPV films is determined mainly by low frequency torsional modes.

The influence of electron-phonon coupling in the emission spectra of self-assembly (SA) films of poly(p-phenylene vinylene) (PPV) is discussed. PPV is an important polymeric system because it exhibits strong luminescence effect. A semi-empirical model was used to analyze the photoluminescence spectra of PPV. This model assumes that defects along the molecule give rise to a distribution of conjugated segments of different lengths. In addition, it was considered that electronic transition was essentially coupled with three effective phonon modes with correspondent energies at 62, -139 and 192 meV, which were observed experimentally.