Dual-functional Bi2Se3 incorporation enables synergistic optimization of carrier and phonon transport in n-type PbS

Lead sulfide (PbS) is a promising mid-temperature thermoelectric material; however, its performance is constrained by the difficulty of simultaneously optimizing electrical transport and suppressing lattice thermal conductivity. Herein, a Bi2Se3 incorporation strategy is developed to synergistically regulate carrier and phonon transport in n-type PbS. The introduced Bi3+ ions partially occupy interstitial sites in the PbS lattice, acting as efficient electron donors and substantially increasing the carrier concentration, thereby enhancing the electrical conductivity and power factor. Meanwhile, residual Bi2Se3 secondary phases generate additional phonon scattering centers and, together with point defects and grain boundaries, establish multiscale phonon scattering, leading to a pronounced reduction in lattice thermal conductivity from 3.04 to 1.70 W m−1 K−1 at room temperature. Benefiting from the concurrent optimization of electronic and thermal transport, the PbS-1.5 mol. % Bi2Se3 sample achieves a maximum power factor of ∼1.02 mW m−1 K−2 and a peak ZT of ∼1.0 at 878 K, together with an average ZT of ∼0.56 over 320–878 K. This work establishes a dual-functional Bi2Se3 incorporation strategy that simultaneously activates carrier transport and intensifies phonon scattering, providing a viable pathway toward high performance PbS-based thermoelectrics.