Synergistic effects improve thermoelectric properties of zone-melted n-type Bi2Te2.7Se0.3

Bismuth telluride (Bi2Te3) is the commercially used thermoelectric material near room temperature, and the widely-adopted zone-melting method is suitable for mass production. However, the ZT value of commercial n-type Bi2Te3 is still maintained around 1.0 and severely restrict the further development of thermoelectric applications. In this work, the thermoelectric property of zone-melted n-type Bi2Te2.7Se0.3 material is significantly improved by the synergistical effects of the BiI3 and SnSb2Te4 co-doping. The non-toxic and non-hygroscopic BiI3 is proved to be an effective electron dopant for the n-type Bi2Te2.7Se0.3, leading to the significantly enhanced power factor and partially suppressed bipolar effect. The SnSb2Te4 doping further induces new scattering centers for heat-carrying phonons and results in a relatively low lattice thermal conductivity of 0.72 W m−1 K−1 at 300 K. Consequently, a ZTmax of 1.30 at 325 K and a ZTave (300–500 K) of 1.00 are achieved in the Bi2Te2.7Se0.3 + 0.15 wt% BiI3 + 0.15 wt% SnSb2Te4 sample. This work provides a feasible way to effectively improve the thermoelectric performance of n-type zone-melted Bi2Te3.