Evidence of electron-hole symmetry breaking in poly(p-phenylene vinylene) -: art. no. 195203

We analyze the structural distortions associated with positively and negatively charged states produced upon doping poly (p-phenylene vinylene) (PPV). Vibrational frequencies associated with excitations in these charged states are analyzed on the basis of the valence force field and model-compound approaches. In situ electron paramagnetic resonance measurements confirm the coexistence of paramagnetic and diamagnetic species in segments with different lengths. Moreover, carbon-carbon bond-length deviations calculated for oppositely charged segments with four rings and three vinyl groups (PV32- and PV32+) clearly differ. Our results show unambiguously that electron-hole symmetry is not maintained in doped PPV and are able to explain the difference between electron and hole intrachain mobility in PPV.