Charge Transport in FeCl₃-Doped Polyethylenevinylacetate–Polyoctylthiophene Blends

The results of an experimental study of the temperature (T) dependent dc conductivity σ_dc, T‐dependent thermoelectric power (TEP), and electron spin resonance in a new conducting polyethylenevinylacetate–polyoctylthiophene (EVAPOT) polymer blend doped with FeCl₃ are presented. For a POT content of 20 wt% σ_dc (300 K) varies from 10⁻¹⁰ to 1 Ω⁻¹ cm⁻¹ with increasing doping, while σ_dc(T) fits σ_dc(T) = σ₀ exp [– (T₀/T)^1/2], especially in highly conducting material. In the most heavily doped samples TEP shows metallic behaviour and the charge transport is described by the granular metal model. In lightly doped samples the T‐dependence of TEP follows the T⁻¹-law for band conduction in non‐degenerate crystalline or amorphous semiconductors. This is the first time the latter behaviour is found in conducting polymers.