Improving the thermoelectric performance of polyaniline through a thieno[3,2- <i>b</i> ]thiophene-based π-conjugated additive

This study incorporates Thieno[3,2-b]thiophene (TT-Ch), a highly π-conjugated additive with a thieno–thiophene core, into polyaniline (PANI) to enhance its TE properties. Structural analyses revealed reduced interlayer spacing and a highly homogeneous composite morphology, generating abundant PANI/TT-Ch interfaces that promote energy filtering of low-energy carriers. Optical tests demonstrated a considerable decrease in bandgap, reaching 1.43 eV, indicating enhanced electronic conjugation and carrier transport routes. TE measurements showed a significant improvement in the Seebeck coefficient, which increased from 123.5 μV/K for the composite with 5 wt% TT-Ch. While carrier concentration decreased, a contemporaneous increase in carrier mobility ensured that the electrical conductivity remained strong. Achieving a maximum power factor of 21.3 μW/mK2 marked a considerable achievement for organic small-molecule/polymer composites. Overall, the incorporation of the strongly conjugated TT-Ch molecule effectively restructures the PANI matrix and creates favourable charge-transport pathways, providing a simple molecular design strategy for achieving high-performance organic thermoelectric composites.