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

Abstract

We herein report the significantly improved thermoelectric performance of n-type Bi₂Te_2.7Se_0.3 polycrystalline bulks through band structure engineering achieved by Au-doping. The Seebeck coefficient can be increased for both Bi₂Te_2.7Se_0.3 and Cu-intercalated Bi₂Te_2.7Se_0.3 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 ∼0.88m₀ (Bi₂Te_2.7Se_0.3) to ∼1.06m₀ (Cu_0.008Bi_1.99Au_0.01Te_2.7Se_0.3). As a consequence, a peak thermoelectric figure of merit ZT ∼0.91 was obtained at 320 K for Cu_0.008Bi_1.99Au_0.01Te_2.7Se_0.3, which is ∼40% and ∼25% enhancement in comparison with Bi₂Te_2.7Se_0.3 and Cu_0.008Bi₂Te_2.7Se_0.3, respectively.