High-Performance PANI /Bi₂Te₃ Composites with Significantly Enhanced Seebeck Coefficient via Multi-Interface Engineering

Polyaniline (PANI) is a promising organic thermoelectric material, but its application is limited by the intrinsic trade-off between electrical conductivity ( σ ) and Seebeck coefficient ( S ). Here, we report a multi-interface engineering strategy to enhance the thermoelectric performance of PANI/Bi₂Te₃ composites. HCl-doped PANI (HPANI) and Bi₂Te₃ are mechanically mixed, and a small amount of emeraldine base PANI (PANI-eb) is introduced to construct additional organic–inorganic interfaces. XPS and UV-vis spectroscopy reveal that these interfaces induce partial de-doping of HPANI, progressively widening the optical bandgap from 1.49   eV to 2.96   eV and reducing carrier concentration. Simultaneously, the increased interfacial density creates energy barriers that filter low-energy carriers, enhancing the average carrier mobility. Hall measurements confirm a mobility increase from 39.9 to 118.6   cm²·V⁻¹·s⁻¹ at 10   wt.% PANI-eb, while carrier concentration decreases monotonically. Temperature-dependent transport further supports the energy-filtering mechanism. Optimized hot pressing at 75 °C improves interfacial contact and polymer chain ordering, leading to simultaneous enhancement of σ and S . The resulting composite achieves a room-temperature S of 149.1 μV·K⁻¹, σ of 17.35 S·cm⁻¹, and a power factor of 38.59 μW·m⁻¹·K⁻¹, which is comparable to the best literature values for bulk PANI-based composites. This work demonstrates that rational interfacial design with PANI-eb, combined with moderate thermal treatment, provides an effective strategy to balance σ and S in polymer-based thermoelectric materials.