Enhanced Thermoelectric Performance of Bulk Bismuth Selenide: Synergistic Effect of Indium and Antimony Co-doping

The thermoelectric (TE) performance of pristine Bi₂Se₃is inferior to that of Bi₂Te₃. Therefore, the study on Bi₂Se₃has faced a decline. The lower performance is due to the low power factor and high thermal conductivity. In recent years, single aliovalent doping has been adopted to improve the TE performance of Bi₂Se₃. Here, we adopt an isovalent co-doping approach using indium and antimony to create a manifold enhancement in the TE performance of Bi₂Se₃via the creation of neutral impurities and deep defect states (DDSs). A high figure of merit (ZT = 0.47) is obtained at 473 K for a doping concentration of 0.1 at. %. The TE performance obtained for Bi_2-xIn_xSb_2x/3Se₃, x = 0.1 at. %, is comparable to that obtained in several reports for pristine Bi₂Te₃. Our density functional theory calculation reveals an underlying DDS located at ∼15 eV below the Fermi level. This leads to enhanced electronic properties via density of states optimization induced by the co-doping. The isovalent doping is expected to create neutral impurities, which causes less scattering to conduction electrons while absorbing phonon vibration, thus improving the TE performance.