Enhancing room-temperature thermoelectric performance of n-type Bi2Te3-based alloys via sulfur alloying

Bismuth-telluride-based alloys are the best thermoelectric materials used in commercial solid-state refrigeration near room temperature. Nevertheless, for n-type polycrystalline alloys, their thermoelectric figure of merit (zT) values at room temperature are often less than 1.0, due to the high electron concentration originating from the donor-like effect induced by the mechanical deformation process. Herein, carrier concentration for better performance near room temperature was optimized through manipulating intrinsic point defects by sulfur alloying. Sulfur alloying significantly decreases antisite defects concentration and suppresses donor-like effect, resulting in optimized carrier concentration and reduced electronic thermal conductivity. The hot deformation process was also applied to improve carrier mobility due to the enhanced texture. As a result, a high zT value of 1 at 300 K and peak zT value of 1.1 at 350 K were obtained for the twice hot-deformed Bi2Te2.7Se0.21S0.09 sample, which verifies sulfur alloying is an effective method to improve thermoelectric performance of n-type polycrystalline Bi2Te3-based alloys near room temperature.