Defect engineering via anionic disorders in n-type Bi_1.8Sb_0.2Te₃ alloys: towards enhanced thermoelectric performance at low temperatures

We report on the defect engineering in n-type Bi_1.8Sb_0.2Te₃ end-compound via Te non-stoichiometry (Bi_1.8Sb_0.2Te_3−x) intending to enhance the thermoelectric performance at low and near room temperature regime (10-350 K). Contemplating the asymmetry in electronic and phonon transport, the extrinsic anionic disorders successfully modulate the thermoelectric transport. Systematic manipulation of Te and Bi/Sb vacancies increases the electrical conductivity, leading to the highest power factor of 534 μW mK⁻² at 350 K. The self-doping effect created via anionic disorders resulted in an enhancement in the thermoelectric performance compared to the Bi_1.8Sb_0.2Te₃ compound. Increased ZT values, accompanied by the thermoelectric quality factor, confirm the quality factor as one of the decisive parameters in elevating the thermoelectric performance. The sample with x = 0.08 has the highest ZT value of 0.081 at 350 K. A 174% increase in compatibility factor is also observed, indicating the state-of-the-art applicability of Bi_1.8Sb_0.2Te₃ in segmented thermoelectric generators.