Resonance raman spectra of SO/sub 3/-doped poly(p-phenylenevinylene)

Summary form only given. Poly(p-phenylenevinylene) (C/sub 6/H/sub 4/CH=CH)/sub n/ (abbreviated as PPV) is a polymer with a prototypical nondegenerate ground-state, which shows high electrical conductivities upon doping. The mechanism of electrical conduction in conducting polymers has been discussed in terms of the self localized excitations (polarons and bipolarons in the case of PPV) created by doping. Recently, we have demonstrated that resonance Raman spectroscopy with visible and near-infrared excitations is useful for characterizing the self-localized excitations in doped conducting polymers. In the present study, we report the resonance Raman spectra of S0sub 3/-doped PPV (electrical conductivity, 10 S cm/sup -1/) excited with visible and near-infrared laser lines. The observed Raman spectra are analyzed by referring to the data of the radical cation and dication species of the model compounds CH/sub 3/(C/sub 6/H/sub 4/CH=CH)nC61-14CH3 (PVn, n=1-3), which well represent the spectroscopic properties of PPV. The radical cations and dications of the model compounds correspond, respectively, to positive polarons and positive bipolarons in the doped polymer. In the 632.8-nm excited resonance Raman spectrum of S0/sub 3/-doped PPV, positive polarons are observed. However, positive bipolarons and neutral parts are observed in the 1064-nm excited resonance Raman spectrum. These results are simillar to those of H/sub 2/S0/sub4/-treated PPV, suggesting that a polaron lattice (a regular array of polarons) may be formed in S0/sub 3/-doped PPV. The effect of doping level on the formation of self-localized excitations in S0/sub 3/-doped PPV will also be discussed.