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

Abstract

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 (m*) 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 ZT (ZTmax) of ~1.6 at 873 K and an average ZT (ZTave) of ~1.25 at 300 to 873 K in SnS0.91Se0.09 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.

Extended anharmonic collapse of phonon dispersions in SnS and SnSe

“…SnS is particularly suitable as an absorber in solar cells due to its high optical absorption coefficient and direct bandgap E g ≃ 1.3 eV (ref. 5 ), and has recently demonstrated fast improvements in thermoelectric efficiency 6,7 . Its bulk electronic structure is also attracting strong interest for valleytronics applications 8 .…”

High thermoelectric performance of rapidly microwave-synthesized Sn1−δS

“…However, there is still room for improvement in the thermoelectric performance of this system. This is evidenced by the recent work on the synthesis by ball-milling of Sn 0.99 Ag 0.005 S. 72 The enhancement of the charge carrier concentration by Ag-doping and the vacancy engineering produces a maximum value of ZT E 1.1 at 877 K. Even more impressive is the result found by He et al 39 for the SnS 0.91 Se 0.09 crystals. A ZT average value of 1.25 was measured in the temperature range from 300 K to 873 K.…”

“…9 shows the Pisarenko plot calculation applying the single parabolic band (SPB) model and assuming carrier scattering dominated by acoustic phonons (ESI, ‡ eqn (S2)). 73,74 Although SnS crystals show a complex three-valence-band transport feature, 39 this model has already been successfully applied to polycrystalline SnS samples. 69,72 The model, as applied here, includes the influence of band degeneracy within the effective mass (m eff ), i.e.…”

“…38 This indicates that there is enormous potential to make significant advances in the preparation of environmentally friendly SnS-based compounds, which are constituted by low-cost and high abundance elements and can be considered as appealing TE materials for large-scale applications. 38,39 Tin chalcogenides, and specifically SnS, are generally produced by a prolonged annealing process (days) of stoichiometric amounts of high-purity precursors in an evacuated sealed tube. 40 This effective method presents some disadvantages, such as the need of operating at high temperatures to accelerate the diffusion between precursors, a non-accurate control of the stoichiometry when using volatile reagents (as sulphur) and the need for intermediate grindings, besides being a high energy and time consuming process.…”

High‐Performance GeTe‐Based Thermoelectrics: from Materials to Devices

“…[ 10–16 ] The thermoelectric devices composed of various thermoelectric materials have the advantages of being stable, reliable, without moving parts, noise‐free and emission‐free, which can also be designed being flexible. [ 17–19 ] Their energy conversion efficiency is governed by a dimensionless figure of merit, ZT [ 20–25 ] where, S is the Seebeck coefficient, σ is the electrical conductivity, S 2 σ is an intact part defined as the power factor to measure the electrical performance, and κ is the thermal conductivity. κ includes electrical thermal conductivity (κ e ) and lattice thermal conductivity (κ l ).…”