Ultra-low lattice thermal conductivity and high figure-of -merit in Cl and K co-dopped Bi2Se3 prepared by KCl flux

Abstract

Bismuth telluride (Bi2Te3) is a widely used thermoelectric (TE) material in practical applications. However, it contains expensive and toxic tellurium, a promising TE material should include low-cost and non-toxic element. Bismuth selenide (Bi2Se3) is similar to Bi2Te3 in electronic and crystal structure. The electron effective mass of Bi2Se3 is smaller than that of Bi2Te3, while its electrical transport performance is inferior to that of Bi2Te3. Therefore, in this study, Cl and K co-doped Bi2Se3 thermoelectric material with high density, low thermal conductivity, and excellent thermoelectric performance was prepared using KCl as the solvent. It is found that the effective electron mass and carrier concentration of the doped sample is effectively improved, which significantly increases the doped sample's electrical transport properties and ZT value. Finally, the Bi2Se3(KCl)3.5 sample reached a maximum ZT value of 0.79 at 550 K, and the average ZT in the measured temperature range reached 0.45.