High thermoelectric performance in low-cost SnS _0.91 Se _0.09 crystals

Thermoelectric technology allows conversion between heat and electricity. Many good thermoelectric materials contain rare or toxic elements, so developing low-cost and high-performance thermoelectric materials is warranted. Here, we report the temperature-dependent interplay of three separate electronic bands in hole-doped tin sulfide (SnS) crystals. This behavior leads to synergistic optimization between effective mass (<i>m</i>*) and carrier mobility (μ) and can be boosted through introducing selenium (Se). This enhanced the power factor from ~30 to ~53 microwatts per centimeter per square kelvin (μW cm^-1 K^-2 at 300 K), while lowering the thermal conductivity after Se alloying. As a result, we obtained a maximum figure of merit <i>ZT</i> (<i>ZT</i> _max) of ~1.6 at 873 K and an average <i>ZT</i> (<i>ZT</i> _ave) of ~1.25 at 300 to 873 K in SnS_0.91Se_0.09 crystals. Our strategy for band manipulation offers a different route for optimizing thermoelectric performance. The high-performance SnS crystals represent an important step toward low-cost, Earth-abundant, and environmentally friendly thermoelectrics.