Realizing broad-range thermoelectric performance in PbS through distorting rock-salt lattice

Lattice distortion realized by entropy engineering can significantly optimize thermoelectric performance through intensifying phonon scattering. However, excessive lattice distortion in high-entropy materials inevitably hinders carrier transport, thereby limiting the wide-temperature average ZT (ZT_ave) value. To enhance the wide-temperature thermoelectric performance of low-cost PbS-based compounds, this work introduces moderate lattice distortion by controlling the entropy around 1.0R (R is the gas constant) to balance phonon and carrier transport, alleviating restrictions on carrier mobility. Firstly, substantial Se and Te alloying in PbS induces rock-salt lattice distortion, which effectively impedes phonon propagation, thus suppressing the lattice thermal conductivity (κ_lat) from 2.41 W m⁻¹ K⁻¹ in PbS to 0.66 W m⁻¹ K⁻¹ in PbS_0.5Se_0.35Te_0.15 at 300 K. Additionally, Cu interstitials are introduced into the lattice-distorted PbS_0.5Se_0.35Te_0.15 to further optimize the carrier density and weighted carrier mobility (μ_W), leading to a significant improvement in μ_W/κ_lat parameter at 300–773 K. Finally, a room-temperature ZT of 0.53 and a maximum ZT of 1.44 are obtained in a PbS_0.5Se_0.35Te_0.15-1%Cu sample, which contributes to an impressive ZT_ave of 1.08 at 300–773 K and a maximum power generation efficiency (η_max) of 7.5%. The results outperform previously reported cost-effective PbS-based compounds and highlight the importance of lattice distortion regulation in enhancing wide-temperature thermoelectric performance.