Point Defect Engineering: Co‐Doping Synergy Realizing Superior Performance in n‐Type Bi2Te3 Thermoelectric Materials

Bi2 Te3 has attracted great attention because of its excellent thermoelectric (TE) performance around room temperature. However, the TE property of the n-type Bi2 Te3 is still relatively low compared to the p-type counterpart, which seriously hinders its commercial application with a combination of the n-type and p-type materials. Herein, an effective process of Cl and W co-doping is employed into the n-type Bi2 Te3 materials to enhance its TE properties. The Bi1.996 W0.004 Te2.476 Cl0.024 Se0.5 sample achieves a peak and average ZT over 1.3 and 1.2, respectively, at temperature range of 300-575 K. A 24-leg TE module of this n-type material and a home-made p-type Bi2 Te3 sample can produce a high efficiency over 6% at a temperature gradient of 235 K, which possesses a 71% improvement compared with a commercial Bi2 Te3 module. This high performance is ascribed to the effect of the Cl and W doping. This co-doping not only significantly increases the Grüneisen parameter but also successfully induces interstitial atoms in the van der Waals gap, which lead to a low lattice thermal conductivity (κl ) of 0.31W m-1 K-1 and a boosted charge transport. This finding represents an important step to promote the development of the n-type Bi2 Te3 materials.