Electronic and optical properties of neutral and charged poly (p-phenylene vinylene )

Electronic and optical properties of a conjugated polymer, poly (p-phenylene vinylene) (PPV), are theoretically studied. Long-range interactions among π electrons as well as electron-lattice coupling are taken into account in both neutral and charged states of a PPV chain by applying the Pariser-Parr-Pople model with intermediate interaction strength. This model coupled with the single-excitation configuration interaction method gives an excitation energy diagram for neutral PPV, consistent with experiment. The optical absorption spectrum is calculated in a wide frequency range, and its polarization dependence and spectral features are analyzed in detail. A polaron state in doped PPV is investigated, and its spatial pattern and absorption spectrum calculated. Its spin density gives an electron-nuclear double resonance spectrum, which is in good agreement with experiment. The present model provides a unified description of the electronic properties of neutral and doped PPV.