Carrier–phonon decoupling via annealing enhances thermoelectric performance of Bi2(Te,Se)3

Thermoelectric cooling based on the Peltier effect requires high-performance materials near room temperature. While Bi2Te3 remains the most viable commercial thermoelectric material, n-type Bi2Te3−xSex (BTS) lags behind its p-type counterpart due to intrinsic anisotropy. In this work, Bi2Te2.6Se0.4 synthesized by melting-hot pressing followed by 100 h annealing (MT-HP-AN) at 723 K exhibits markedly improved performance. Annealing introduces cation vacancies via Te(Se) volatilization, lowering carrier density and enhancing mobility, while simultaneously increasing phonon scattering. A peak ZT of 1.06 at 373 K and an average ZT of 0.99 at 300–423 K are achieved. This MT-HP-AN approach offers a simple yet effective strategy to decouple carrier and phonon transport, advancing the potential of n-type BTS for thermoelectric cooling applications.