Electrical properties of poly(tetrathiafulvalenes)

Results of conductivity measurements on undoped and iodine or bromine doped poly(tetrathiafulvalenes) are reported. At higher temperatures the temperature dependence of the d.c. conductivity can be best described by σ d.c. = ° o . exp(T/T o ) 1/4 , typical for variable range hopping. The a.c. conductivity follows the general law °(ω) ∼ ω 2 for frequencies higher than a critical frequency. A description of the frequency dependent conductivity is given by the extended pair approximation (EPA). At lower temperatures a deviation from linearity of the function in σ versus T −1/4 is observed.