Temperature dependence of the electrical conductivity ofAsF5-doped poly(p-phenylene vinylene)

The electrical conductivity σ(T) in poly(p-phenlyene vinylene) (PPV) heavily doped with ${\mathrm{AsF}}_5$ has been measured as a function of temperature for 4.2<T<300 K. Films which can be oriented were prepared by a soluble-polymer precursor route and were investigated in the as-doped state and after aging by exposure to air. PPV with σ(300 K)<∼100 (Ω cm${)}^{\mathrm{-}1}$ has a temperature dependence given by σ(T)∼${\sigma }_0$ exp[-($T_0$/T${)}^{\alpha }$], (1/4≤α≤ 1) / 2 , independent of the sample history. For samples with higher room-temperature conductivity, the temperature dependence for T<100 K is well represented by a power law of the form σ=$a_0$+${\mathrm{bT}}^{1/2}$; $a_0$ generally decreases with decreasing σ(300 K) and becomes negative for σ(300 K)<∼300 (Ω cm${)}^{\mathrm{-}1}$. The latter results are consistent with a metal-insulator transition.