Carrier concentration optimization and dynamic doping enhance the thermoelectric performance of n-type PbS over a wide temperature range

Thermoelectric materials are essential for converting waste thermal energy directly into usable electrical energy and vice versa. This capability significantly enhances the efficiency of fossil energy conversion and contributes to environmental protection. Exceptional thermoelectric materials must exhibit both a high power factor and a low total thermal conductivity. Achieving a high power factor over a wide temperature range while maintaining a relatively low lattice thermal conductivity is critical for obtaining a high average figure of merit, which is vital for improving the efficiency of thermoelectric conversion across various temperatures. Optimizing a single thermoelectric parameter alone does not significantly improve the overall properties of the material. Therefore, contemporary thermoelectric research focuses on effectively regulating these parameters to enhance the ZT value. Lead chalcogenides, PbQ (where Q = Te, Se, or S), are mid-temperature thermoelectric materials renowned for their stable properties and excellent performance. PbTe, in particular, is a typical thermoelectric material that maintains a stable crystal structure and avoids phase transitions within its operational temperature range. It features a highly symmetric electronic band structure and a complex phonon band structure, which facilitates versatile control over its thermoelectric performance. However, the limited availability and high cost of tellurium in conventional PbTe compounds may constrain their widespread applications. As a result, PbS-based thermoelectric materials have attracted significant attention due to their abundant elemental resources, low cost, and high thermal stability. Current research on PbS focuses primarily on enhancing its carrier concentration through heavy element doping to achieve superior thermoelectric performance at medium to high temperatures. However, this approach often results in poor thermoelectric performance near room temperature, severely limiting its applications in thermoelectric cooling technologies. In this work, the carrier concentration of n-type PbS is synergistically regulated through the inclusion of trace amounts of GaBi, resulting in a PF of 21.70 mu W cm(-1) K-2 at room temperature. Meanwhile, the formation of Ga/Bi interstitial atoms and dislocation defects enhances phonon scattering, thereby reducing the lattice thermal conductivity of PbS. The ZT(ave) of Pb-0.99875(GaBi)(0.00125)S reaches 0.58 in 300-773 K. To further optimize the thermoelectric performance of n-type PbS over a wide temperature range, Cu atoms are introduced to realize dynamic doping of the carrier concentration. The PFave of Pb-0.99875(GaBi)(0.00125)S+2%Cu increases to 17.6 mu W cm(-1) K-2, and the ZT(ave) is further increased to 0.65. This work provides a new method for optimizing the thermoelectric performance of PbS near room temperature, which is crucial for advancing the application of PbS-based thermoelectric materials in thermoelectric refrigeration.