INSITU ABSORPTION-SPECTRA MEASUREMENTS IN POLY(1,4-NAPHTHALENE VINYLENE) DURING ELECTROCHEMICAL DOPING

The electrochemical and optical properties of poly(1,4-naphthalene vinylene) (PNV) during electrochemical p-type doping have been investigated by the cyclic voltammetry and in situ optical absorption spectrum measurements. The evolution of localized states is evidenced by the spectral change with electrochemical doping. These results are discussed in terms of polaron and/or bi-polaron models. The band gap of PNV was evaluated to be about 2.3 eV and that of poly(p-phenylene vinylene) (PPV) to be smaller by about 0.4 eV. This result can be interpreted in terms of a more effective resonance interaction between the naphthalene unit and the vinylene unit. The electronic band structure of PNV was determined. The polaron states in PNV appear in the band gap: about 0.5 eV above the valence band and about 0.5 eV below the conduction band. The bottom of the conduction band of PNV is about 0.3 eV lower than that of PPV and successful n-type doping in PNV is expected.