Charge transport of lithium-salt-doped polyaniline - art. no. 035101

Charge transport properties, including temperature-dependent de conductivit y and thermoelectric power are reported for Li-salt (LiPF6, LiBF4, LiAsF6, LiCF3SO3, or LiClO4) -doped polyaniline (PAN) samples. The experiments of e lectron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy ( ICPS) are performed for the systems. The electrical and magnetic properties and the doping mechanism of various Li-salt-doped PAN samples are compared with those of hydrochloric-acid (HCl) -doped PAN samples. The PAN material s doped with LiPF6 have the highest de conductivity (sigma (dc)similar to1 S/cm, at room temperature) in the Li-salt-doped PAN systems studied here. T he temperature dependence of sigma (dc) Of the systems follows a quasi-one- dimensional variable range hopping model, which is similar to that of HCl-d oped PAN samples. As the molar concentration increases from similar to 10(- 4) M to similar to1 M, the system is transformed from an insulating to cond ucting (non-metallic) state. From EPR experiments, we measure the temperatu re dependence of magnetic susceptibility, and obtain the density of states for various Li-salt-doped PANs with different doping levels. We observe the increase of the density of states as the molar concentration increases. Fr om the analysis of nitrogen 1s peak obtained from XPS experiments, we estim ate the doping level of the systems. We compare the effective doping thickn ess between HCl-doped PAN samples and Li-salt-doped PAN ones, based upon th e results of XPS argon (Ar) ion sputtering experiments. The diffusion rate of Li+ or counterions and the dissociation constants of Li salt in doping s olution play an important role for the effective doping and transport prope rties of the Li-salt-doped PAN samples.