Interfacial energy band and phonon scattering effect in Bi₂Te₃-polypyrrole hybrid thermoelectric material

We hybridized n-type Bi₂Te₃ with an inexpensive and abundantly available conducting polymer, polypyrrole, to obtain a bulk-structured hybrid material in which the interfacial energy band and the phonon scattering effects should occur at the interface of the two components. The obtained hybrid material inevitably exhibited a lower electrical conductivity than pristine Bi₂Te₃, which may be attributable to carrier scattering at the interfacial energy barrier. However, the hybrid material completely compensated for this loss in electrical conductivity with a significant increase in the Seebeck coefficient, and thus it retained the power factor with no loss. In addition, the hybrid material displayed a much lower thermal conductivity than pristine Bi₂Te₃ owing to the phonon scattering effect. The hybrid material exhibited significant decoupling of the electrical and thermal properties, thus affording state-of-the-art figures of merit (ZT ∼ 0.98 at 25 °C, ZT_max ∼ 1.21 at 100 °C, and ZT_ave ∼ 1.18 at 50–150 °C) that exceed those of most of the previously reported n-type Bi₂Te₃ or Bi₂(Te,Se)₃ materials.