Enhancing thermoelectrics of Bi2Te3-Sb2Te3 alloys via anion-cation dual-site doping

Bi2Te3 is a well-established and environmentally friendly thermoelectric material, typically optimized for electrical transport properties through adjustments in carrier concentration and band engineering. Meanwhile, lattice thermal conductivity is suppressed via defect engineering to achieve excellent performance at room temperature. However, its high-temperature performance is limited by bipolar diffusion that becomes more pronounced at elevated temperatures. This study focuses on enhancing the thermoelectric performance of p-type Bi0.3Sb1.7Te3 bulk materials at high temperatures by introducing a Cd/Se anion-cation dual-site doping strategy. Through optimization of carrier concentration and enhancement of the Seebeck coefficient, the weighted mobility (mu(w)) is significantly improved, leading to a substantial increase in the power factor over the entire temperature range. The defect structure, arising from cation-anion dual-site doping and porosity, promotes enhanced phonon scattering, thereby reducing lattice thermal conductivity and suppressing bipolar diffusion. Ultimately, this dual approach results in synergistic improvements in both electronic and phonon transport properties, achieving electron-phonon decoupling and enhancing thermoelectric performance across the full temperature range. A peak zT of similar to 1.1 at 400 K and an average zT of similar to 1.0 from 303 to 503 K are achieved. This work provides a valuable reference for the optimization of thermoelectric performance in p-type Bi2Te3 materials.