Temperature dependence of DC-conductivity in poly(3-alkylthiophenes) in temperature regime 20-400 K

We present recent results on the effect of side chain length and thermal dedoping on the temperature dependence of the conductivity above room temperature. The temperature dependence of the dc-conductivity in heavily doped poly(3-alkylthiophenes) changes above room temperature: instead of increasing with increased temperature, as at low temperatures, the conductivity decreases after reaching a maximum between 300 and 370 K. This effect is not due to thermal dedoping, which should be an irreversible process (or at least a function of both time and temperature). We propose that this maximum is caused by the disorder resulting from the thermochromic transition. Below 300 K the temperature dependence is in good agreement with thermal fluctuation induced tunneling model (σ=σ_∞exp(-T₁(T₀+T)). We will discuss the anisotropy of conductivity in stretched samples in low temperature.