Electrical and Optical Properties of Poly(p-phenylene) Film and Their Doping Effect

Poly(p-phenylene) films with a conductivity of ca. 100 S/cm are synthesized by a new method of electrical oxidation of benzene using the composite electrolytes of CuCl₂/LiAsF₆. An in situ study of the absorption spectra of the poly(p-phenylene) films during the electrochemical doping with AsF₆ has been carried out. From the absorption spectrum of undoped state, we find a strong absorption peak at ca. 3.4 eV which is associated with the transition from ground-state to excited-state. The remarkable changes of the absorption spectra below the photon energy of 3.0 eV are observed, which are related to the polaron and/or bipolaron states of this polymer. The electrochemical n-type doping is also demonstrated.