Inhibition of minority transport for elevating the thermoelectric figure of merit of CuO/BiSbTe nanocomposites at high temperatures

Achieving a large thermoelectric figure of merit (ZT) value at elevated temperatures for Bi2Te3-based materials is significant for low-grade waste-heat (∼400–500 K) recovery applications. Here, we show that in Bi0.4Sb1.6Te3 based composites incorporated with 0.2 vol% CuO nanoinclusions, the introduced asymmetric interface potentials can effectively inhibit the transport of minorities through stronger scattering than majorities, as well as the energy filtering effect, thus resulting in an obvious increase (∼8% rise) of power factor at high temperatures. In addition to enhanced phonon scattering at interfaces and nanoinclusions, the reduced thermal conductivity (∼65% decline) at elevated temperatures can be attributed to inhibition of bipolar contributions through strong scattering of minorities at the interface potentials. Consequently, in BiSbTe-based thermoelectric systems with 0.2 vol% CuO, a largest ZT = 1.37 is achieved at 496 K, which is ∼40% larger than that of the BiSbTe matrix at the same temperature.