Effect of dopant-molecule size on the electrical conductivity of polyacetylene

Abstract

We have measured the temperature dependence of the conductivity of cis-polyacetylene doped with iodine and with ${\mathrm{H}}_{2}$Ir${\mathrm{Cl}}_{6}$\ifmmode\cdot\else\textperiodcentered\fi{}6${\mathrm{H}}_{2}$O. The iodine dopant was introduced from the vapor phase under various vapor pressures and also from solution. The Ir${\mathrm{Cl}}_{6}$ was introduced from solution. We find $log\ensuremath{\rho}\ensuremath{\propto}{T}^{\frac{\ensuremath{-}1}{4}}$ for $(\mathrm{CH}){\mathrm{I}}_{y}$ and $log\ensuremath{\rho}\ensuremath{\propto}{T}^{\frac{\ensuremath{-}1}{2}}$ for ${(\mathrm{CH})}_{x}$ doped with Ir${\mathrm{Cl}}_{6}$. We attribute the difference to separate transport mechanisms. We suggest that the size and shape of the dopant molecule is the controlling variable rather than the doping conditions.