Electronic properties of neutral and polaron states in poly(p-phenylene vinylene)

We show that the Pariser-Parr-Pople model with the intermediate strength of electron-electron interaction provides the electronic properties both for neutral and polaron states in poly(p-phenylene vinylene) (PPV), which are consistent with experiments. Within the single-excitation configuration-interaction method, optical gap is 2.4 eV with the exciton binding energy of 0.8 eV for neutral PPV, in agreement with optical and photocurrent measurements. The polarization dependence and spectral features of optical absorption are analyzed in a wide frequency range. The electron-nuclear-double resonance spectra calculated based on the spin density profile of a polaron within the unrestricted Hartree-Fock method explain satisfactorily the experimental spectra for undoped sample in dark state. This strongly supports that the observed π-radicals are trapped polarons.