Hall effect analysis of conducting doped poly(3,4-ethylenedioxythiophene) (PEDOT) using band and hopping transport mechanisms

Hall effect and electrical conductivity measurements were performed on poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) treated with sulfuric acid (PEDOT:Sul) in the temperature range between 21 and 301 K. The observed temperature dependence of the electrical conductivity was expressed as the sum of the metallic band conductivity and variable-range hopping conductivity. The contribution of metallic band conduction was large, indicating that metallic domains are created upon H₂SO₄ treatment. The charge number density directly derived from the Hall effect was extremely large, on the order of 10²³ cm⁻³, which is called the “improper” Hall effect. Assuming that only delocalized band carriers contribute to the Hall effect, we obtained the charge number densities in metallic conduction using the decomposed conductivities for metallic conduction and variable-range hopping conduction. The obtained values ranged between (3.1 ± 0.2) × 10²¹ and (4.7 ± 0.3) × 10²¹ cm⁻³.