Lower-cost thermoelectrics: Thermoelectric materials convert heat to electricity, making them attractive for heat harvesting or cooling applications. However, many high-performance thermoelectrics are made of expensive or toxic materials. He et al. found that a material composed of primarily tin and sulfur could be optimized to have relatively good thermoelectric properties. Introducing about 10% selenium to tin sulfide helped tune these properties by electronic band manipulation. This material is a step toward more earth-abundant, less toxic, and lower-cost thermoelectrics than the telluride-based materials currently in use. Science , this issue p. 1418

PbSe-based thermoelectric materials exhibit promising ZT values at medium temperature, but its near-room-temperature thermoelectric properties are overlooked, thus restricting its average ZT (ZT_ave) value at low-medium temperatures. Here, a high ZT_ave of 0.90 at low temperature (300–573 K) is reported in n-type PbSe-based thermoelectric material (Pb_1.02Se_0.72Te_0.20S_0.08−0.3%Cu), resulting in a large ZT_ave of 0.96 at low-medium temperatures (300–773 K). This high thermoelectric performance stems from its ultralow lattice thermal conductivity caused by dense dislocations through heavy Te/S alloying and Cu interstitial doping. The dislocation density evaluated by modified Williamson-Hall method reaches up to 5.4 × 10¹⁶ m⁻² in Pb_1.02Se_0.72Te_0.20S_0.08−0.3%Cu. Moreover, the microstructure observation further uncloses two kinds of dislocations, namely screw and edge dislocations, with several to hundreds of nanometers scale in length. These dislocations in lattice can strongly intensify phonon scattering to minimize the lattice thermal conductivity and simultaneously maintain high carrier transport. As a result, with the reduced lattice thermal conductivity and optimized power factor in Pb_1.02Se_0.72Te_0.20S_0.08−0.3%Cu, its near-room-temperature thermoelectric performance is largely enhanced and exceeds previous PbSe-based thermoelectric materials.

Lead sulfide (PbS) presents large potential in thermoelectric application due to its earth‐abundant S element. However, its inferior average ZT (ZT_ave) value makes PbS less competitive with its analogs PbTe and PbSe. To promote its thermoelectric performance, this study implements strategies of continuous Se alloying and Cu interstitial doping to synergistically tune thermal and electrical transport properties in n‐type PbS. First, the lattice parameter of 5.93 Å in PbS is linearly expanded to 6.03 Å in PbS_0.5Se_0.5 with increasing Se alloying content. This expanded lattice in Se‐alloyed PbS not only intensifies phonon scattering but also facilitates the formation of Cu interstitials. Based on the PbS_0.6Se_0.4 content with the minimal lattice thermal conductivity, Cu interstitials are introduced to improve the electron density, thus boosting the peak power factor, from 3.88 μW cm⁻¹ K⁻² in PbS_0.6Se_0.4 to 20.58 μW cm⁻¹ K⁻² in PbS_0.6Se_0.4−1%Cu. Meanwhile, the lattice thermal conductivity in PbS_0.6Se_0.4−x%Cu (x = 0–2) is further suppressed due to the strong strain field caused by Cu interstitials. Finally, with the lowered thermal conductivity and high electrical transport properties, a peak ZT ~1.1 and ZT_ave ~0.82 can be achieved in PbS_0.6Se_0.4 − 1%Cu at 300–773K, which outperforms previously reported n‐type PbS.

Carrier mobility is a key parameter for thermoelectric performance. A high average ZT value of ∼1.13 can be achieved in n-type PbSe–18%SnS–0.5%Cu at 300–873 K through the rational optimization of carrier mobility.