Thermoelectric properties and intrinsic conduction processes in DBSA and NaSIPA doped polyanilines

Abstract

Seeking to gain fundamental understanding of the thermoelectric (TE) behavior of polyanilines (PANIs), structure- property relationships of PANI nanorods, doped with dodecylbenzenesulfonic acid (DBSA) and 5-sulfoisophtalic acid sodium salt (NaSIPA), and prepared by an indirect synthetic route, are discussed in terms of the contribution of the acid concentrations on the thermoelectric properties. The synergistic combination of high doping level and layer structure, accounts for the moderately high electrical conductivities (σ) and low constant Seebeck coefficients (α) of PANI-DBSA. Conversely, the poor doping ability of NaSIPA and low crystallinity degree explain the low electrical conductivities along with significant increases in Seebeck coefficient values. In relation to conduction mechanisms, PANI-DBSA shows a hopping behavior with a carrier concentration of c≈0.49 (hole type), while PANI-NaSIPA displays a diffusive regime, characteristic of degenerate metallic semiconductors, with an estimated charge carrier density of n≈3 × 1021 e/cm3.