Enhanced phonon scattering and thermoelectric performance for N-type Bi2Te2.7Se0.3 through incorporation of conductive polyaniline particles

Bi2Te3 based alloys are the state-of-art thermoelectric materials at/near room temperatures. However, the per-formance of n-type Bi2Te3 is much difficult to improve as compared to p-type Bi2Te3. Here, we show that via incorporation of 1.5 wt% conductive polyaniline nanoparticles in Bi2Te2.7Se0.3 the lattice thermal conductivity of the composite system reduces by 49 % at 300 K mainly due to enhanced phonon scattering by the polymer inclusions. Moreover, energy-dependent carrier scattering occurs owing to the interfacial potentials formed at the inorganic/organic boundaries, leading to 8 % elevation of thermopower in the sample, which counteracts the decrease of electron mobility to a large degree. As a result, both a maximum figure of merit Zmax = 3.57 x 10-3 K-1 (300 K) and a maximum dimensionless figure of merit ZTmax = 1.22 (345 K) are achieved for the composite sample with 1.5 wt% PANI inclusions, which are respectively -42 % and -46 % larger than those of pristine Bi2Te2.7Se0.3, demonstrating that incorporation of nanophase polyaniline in Bi2Te2.7Se0.3 is an effective strategy to enhance its thermoelectric performance.