POSITIVE THERMOELECTRIC-POWER OF ALKALI-METAL-DOPED POLYACETYLENE

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 anisotropy ratios sigma(parallel to)/sigma(perpendicular to), for the stretch-oriented samples indicate a quasi-one dimensional charge transport characteristic in heavily doped polyacetylene. Also, we report the positive TEP of alkali-metal-doped polyacetylene. The temperature dependent TEP of K-dope polyacetylene is quasi-linear, which is characteristic 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 eta(E(F))=0.19 states/eV C atom. The positive sign of TEPs for alkali-mental-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.