High Carrier Mobility in N-Type PbS_0.6Se_0.4 Crystal Enhances Thermoelectric Properties and Module Performance

Thermoelectric technology has significant applications in waste heat harvesting and temperature control of electronic devices. PbS has long been seen as a robust candidate for large-scale thermoelectric applications due to its low cost and high mechanical strength. However, the low ZT near room temperature hinders its further application. In this work, Sn alloying, Ga doping, and crystal growth are applied to optimize the electrical transport properties and thus the near-room-temperature thermoelectric performance. Specifically, Sn alloying enhances the carrier concentration by narrowing the bandgap. Then, Ga doping further enhances the carrier concentration while maintaining the carrier mobility. Lastly, growing the crystal significantly increases the carrier mobility by 34%, reaching ≈587 cm² V⁻¹ S⁻¹, among the highest reported for PbS. Ultimately, a high room temperature ZT of ≈0.6 and a high average ZT of ≈0.9 (300–823 K) are obtained. The power generation efficiency of a single leg module reaches ≈7.1% at a temperature difference (ΔT) of ≈405 K. A 7-pair PbS-based thermoelectric cooling module is further established, achieving a ΔT of ≈40 K at room temperature and a maximum ΔT of ≈51 K when T_h = 343 K. The work indicates that PbS-based material has practical application potential in both thermoelectric cooling and power generation.