Enhanced Thermoelectric Properties of p-Type Bi 0.5 Sb 1.5 Te 3 -Cu 8 GeSe 6 Composite Materials.

Bismuth-telluride-based thermoelectric materials have been applied in active room-temperature cooling, but the mediocre value of ∼1.0 limits the thermoelectric (TE) device's conversion efficiency and determines its application. In this work, we show the obviously improved thermoelectric properties of p-type BiSbTe by the CuGeSe composite. The addition of CuGeSe effectively boosts the carrier concentration and thus limits the bipolar thermal conductivity as the temperature is elevated. With the CuGeSe content of 0.08 wt %, the hole concentration reaches 5.0 × 10 cm and the corresponding carrier mobility is over 160 cm V s, resulting in an optimized power factor of over 42 μW cm K at 300 K. Moreover, the CuGeSe composite introduces multiple phonon-scattering centers by increasing dislocations and element and strain field inhomogeneities, which reduce the thermal conductivity consisting of a lattice contribution and a bipolar contribution to 0.51 W m K at 350 K. As a consequence, the peak of the BiSbTe-0.08 wt % CuGeSe composite reaches 1.30 at 375 K and the average between 300 and 500 K is improved to 1.13. A thermoelectric module comprised of this composite and commercial BiTeSe exhibits a conversion efficiency of 5.3% with a temperature difference of 250 K, demonstrating the promising applications in low-grade energy recovery.