Positive thermoelectric power of alkali-metal-doped polyacetlene

The experimental results of electrical conductivity and thermoelectric power (TEP) of alkali-metal-doped polyacetylene are presented. The conductivities of (K0.14CH)x and (Rb0.17CH)x follow a power law of temperature. The temperature-independent conductivity anistroscopy ratios σ∥σ⊥ for the stretch-oriented samples indicate a quasi-one dimensional charge transport characteristic in heavily doped polyacetylene. Also, we report the positve TEP of alkali-metal-doped polyacetylene. The temperature dependent TEP of K-doped polyacetylene is quasi-linear, which is characteristics to that of diffusive metals. Taking the slope of the linear temperature-dependent TEP, the density of states at the Fermi level for (K0.14CH)x is estimated to be η(RF)=0.19 states/eV C atom. The positive sign of TEPs for alkali-metal-doped polyacetylene can be understood by the quasi-one dimensional soliton condensed state model. The soliton band is nearly filled, which is possibly due to some compensation from impurities in doped polyacetylene, so that a hole-like charge transport can occur resulting in the positive TEP.