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

Abstract We report on the defect engineering in n-type Bi 1.8 Sb 0.2 Te 3 end-compound via Te non-stoichiometry (Bi 1.8 Sb 0.2 Te 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 1.8 Sb 0.2 Te 3 compound. Increased Z T 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 1.8 Sb 0.2 Te 3 in segmented thermoelectric generators.