Tailored interfacial design via in situ polymer integration enhances thermoelectric performance in Bi₂Te₃

This study introduces a distinct interfacial engineering strategy based on in situ polymer integration, which provides an effective and controllable route for modulating charge and heat transport for the development of a high–performance thermoelectric material. A thermoelectric composite was fabricated via a reproducible one–pot chemical process, in which the conductive polymer was polymerized and simultaneously deposited onto Bi₂Te₃. This approach yielded finely dispersed polymer domains with minimized agglomeration, resulting in increased interfacial contact with Bi₂Te₃. These interfacial contacts promoted energy filtering, inducing energy–dependent carrier scattering and a clear decoupling between electrical resistivity and Seebeck coefficient. The composite also exhibited suppressed thermal conductivity, attributed to enhanced phonon and carrier scattering at the interfacial contacts. These transport behaviors were confirmed by systematic experimental characterization together with complementary theoretical modeling based on the single parabolic band approximation. The composite achieved a maximum ZT of ∼ 1.31 at 477 K and an average ZT of ∼ 1.15 over the temperature range of 300–550 K. In comparison to other low–temperature n–type thermoelectric materials, the composite offers not only excellent thermoelectric performance but also advantages in cost, processability, and flexible device compatibility, making it highly suitable for practical and scalable thermoelectric applications.