Enhanced thermoelectric performance of n-type Cu0.008Bi2Te2.7Se0.3 by band engineering

We herein report the significantly improved thermoelectric performance of n-type Bi2Te2.7Se0.3 polycrystalline bulks through band structure engineering achieved by Au-doping. The Seebeck coefficient can be increased for both Bi2Te2.7Se0.3 and Cu-intercalated Bi2Te2.7Se0.3 bulks by doping Au on the Bi site, either due to the addition of the resonant state or the enhancement of density of states (DOS) effective mass m(d)*. Theoretical calculations combined with experimental measurements showed that band engineering connected with chemical potential tuning results in higher DOS at the bottom of the conduction band and increases the m(d)* from similar to 0.88m(0) (Bi2Te2.7Se0.3) to similar to 1.06m(0) (Cu0.008Bi1.99Au0.01Te2.7Se0.3). As a consequence, a peak thermoelectric figure of merit ZT similar to 0.91 was obtained at 320 K for Cu0.008Bi1.99Au0.01Te2.7Se0.3, which is similar to 40% and similar to 25% enhancement in comparison with Bi2Te2.7Se0.3 and Cu0.008Bi2Te2.7Se0.3, respectively.