Cu 2 Te Incorporation-Induced High Average Thermoelectric Performance in p -Type Bi 2 Te 3 Alloys.

p -Type (Bi, Sb) 2 Te 3 alloys are attractive materials for near-room-temperature thermoelectric applications due to their high atomic masses and large spin-orbit interactions. However, their narrow band gaps originating from spin-orbit interactions lead to bipolar excitation, thereby limiting average thermoelectrics within a local temperature region (300-400 K). Here, we introduce Cu 2 Te into the Bi 0.3 Sb 1.7 Te 3 (BST) lattice to implement high thermoelectrics over a wide temperature range. The carrier concentration is synergistically modulated via Cu substitution and the evolution of intrinsic point defects (antisites and vacancies). Furthermore, the chain effect caused by Cu 2 Te incorporation in BST is reflected in the improvement of the weighted mobility μ W , thereby enhancing the power factor in the whole temperature range. Extrinsic and intrinsic defects due to the incorporation of Cu 2 Te lead to a significant reduction in the lattice thermal conductivity κ L , which is further demonstrated by Raman spectroscopy. Combining κ L and μ W , the quantity factor B increases from 0.5 to 1 with increasing Cu 2 Te content due to not only the reduction of κ L but also a significant improvement in electrical properties. Eventually, a peak figure of merit ( zT ) of ∼1.15 at 423 K is achieved in BST-Cu 2 Te samples, and an average figure of merit ( zT ave ) of ∼1.12 (350-500 K) surpasses other excellent p -type Bi 2 Te 3 -based thermoelectrics. Such a synergistic effect can facilitate near-room-temperature thermoelectric applications of Bi 2 Te 3 -based alloys and provide chances for the technology space in thermoelectrics.