Thermoelectric Performance of Sb₂Te₃-Based Alloys is Improved by Introducing PN Junctions

Interface engineering has been demonstrated to be an effective strategy for enhancing the thermoelectric (TE) performance of materials. However, a very typical interface in semiconductors, that is, the PN junction (PNJ), is scarcely adopted by the thermoelectrical community because of the coexistence of holes and electrons. Interestingly, our explorative results provide a definitively positive case that appropriate PNJs are able to enhance the TE performance of p-type Sb₂Te₃-based alloys. Specifically, owing to the formation of the charge-depletion layer and built-in electric field, the carrier concentration and transport can be optimized and thus the power factor is improved and the electronic thermal conductivity is decreased. Meanwhile, PNJs provide scattering centers for phonons, leading to a reduced lattice thermal conductivity. Consequently, the p-type (Bi₂Te₃)_0.15-(Sb₂Te₃)_0.85 composites comprising PNJs achieve a ∼131% improvement of the ZT value compared with the pure Sb₂Te₃. The increased ZT demonstrates the feasibility of improving the TE properties by introducing PNJs, which will open a new and effective avenue for designing TE alloys with high performance.