Improved thermoelectric performance in polypyrrole/Cu2SnS3 composites

Polypyrrole (PPy) is a promising thermoelectric organic material due to low thermal conductivity, higher electrical conductivity, easy preparation and stability. However, its thermoelectric performance is limited by the intrinsic low Seebeck coefficient. In this paper, PPy/xCu₂SnS₃ (x = 0–5 wt%) composites with enhanced thermoelectric properties were prepared through chemical oxidation method using iron chloride (FeCl₃) as oxidant and methyl orange (MO) as soft template. The obtained composites were investigated by X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and Raman spectroscopy. The Cu₂SnS₃ increased the carrier density and electrical conductivity, meanwhile, thanks to the energy filtering effect and phonon scattering at the organic-inorganic interface of PPy and Cu₂SnS₃, the Seebeck coefficient increased and thermal conductivity decreased for PPy/ xCu₂SnS₃ (x > 0) composites. The highest electrical conductivity (74.571 S/cm) and Seebeck coefficient (11.165 μV/K) at 300 K were obtained from PPy/xCu₂SnS₃ (x = 1 wt%), resulting in a maximum figure of merit (ZT) of 1.646×10⁻³, which is 8.5 times higher than that of pure PPy.