Achieving high thermoelectric performance through constructing coherent interfaces and building interface potential barriers in n-type Bi2Te3/Bi2Te2.7Se0.3 nanocomposites

Abstract

Although Bi₂Te_2.7Se_0.3 is the best n-type thermoelectric material near room temperature, its energy-conversion efficiency η reported so far is still low. Hence, it is imperative to increase its η so as to realize widespread applications in heat recovery. Here, we show that through incorporation of Bi₂Te₃ (BT) nanoinclusions in Bi₂Te_2.7Se_0.3 one can construct a large number of coherent phase boundaries and build effective interface potential barriers, based on which high electron mobility and energy-dependent carrier scattering are realized simultaneously. As a result, as large as 11% elevation of power factor is reached besides a large drop (53% at 300 K) of lattice thermal conductivity in the composite with 0.5 vol% BT nanoinclusions. Consequently, both a record high figure of merit ZT_max = 1.35 (at 414 K) and a record large ZT_ave = 1.28 are achieved in the operating temperature range of 300–525 K, which allow us to obtain an unprecedented conversion efficiency η = 10.5%. The present work demonstrates that incorporation of isostructural nanoinclusions in Bi₂Te_2.7Se_0.3 is an effective approach to improve its thermoelectric performance.