Interfacial Reconstruction Enables Enhanced Thermoelectric Performance in Bismuth Telluride-Based Alloys

Bismuth telluride-based alloys are the benchmark thermoelectric materials for near-room-temperature power generation and solid-state cooling, yet further performance improvements through conventional optimization strategies remain challenging. Here, we introduce an interfacial reconstruction strategy by incorporating SnSe into Bi_0.4Sb_1.6Te₃. Interdiffusion and chemical reconstruction at the Bi_0.4Sb_1.6Te₃/SnSe heterointerfaces synergistically regulate charge-carrier transport and phonon scattering. As a result, the optimized composite achieves a peak dimensionless figure of merit (ZT) of ∼1.38 at 363 K and an average ZT of ∼1.25 across 303-423 K. Moreover, a single-leg thermoelectric device fabricated from this material delivers an energy conversion efficiency of ∼6.47% under a temperature difference of 200 K. These results establish interfacial reconstruction as a simple and effective approach to improving the thermoelectric performance of bismuth telluride-based alloys.