Ultrahigh power factor and thermoelectric performance in hole-doped single-crystal SnSe

Abstract

Heat conversion gets a power boost Thermoelectric materials convert waste heat into electricity, but often achieve high conversion efficiencies only at high temperatures. Zhao et al. tackle this problem by introducing small amounts of sodium to the thermoelectric SnSe (see the Perspective by Behnia). This boosts the power factor, allowing the material to generate more energy while maintaining good conversion efficiency. The effect holds across a wide temperature range, which is attractive for developing new applications. Science , this issue p. 141 ; see also p. 124

Heavy Doping by Bromine to Improve the Thermoelectric Properties of n‐type Polycrystalline SnSe

“…The lowest room temperature thermal conductivity is ≈0.63 W m −1 K −1 for SnSe 0.94 Br 0.06 , lower than 0.72 W m −1 K −1 for SnSe 0.87 I 0.03 S 0.1 , and the lowest thermal conductivity is ≈0.25 W m −1 K −1 at 773 K for SnSe 0.92 Br 0.08 , lower than ≈0.30 W m −1 K −1 for SnSe 0.87 I 0.03 S 0.1 and ≈0.32 W m −1 K −1 for SnSe 0.97 Br 0.03 . This low thermal conductivity (at 773 K) is comparable to the results for single crystals measured along the a axis (e.g., 0.23 W m −1 K −1 for undoped SnSe and 0.27 W m −1 K −1 for Na‐doped SnSe) 17, 29. With increasing content of Br, the thermal conductivity at 773 K decreased.…”

Low Sound Velocity Contributing to the High Thermoelectric Performance of Ag8SnSe6

“…This should lead to its electronic performance not as promising as conventional thermoelectrics, which can be seen from the temperature‐dependent Seebeck coefficient and resistivity as shown in Figure 4 a,b, respectively. The resulting maximum thermoelectric power factor ( S 2 / ρ ) of ≈6 μW cm −1 K −2 is much lower than 20–40 μW cm −1 K −2 that is normally seen in conventional thermoelectrics 6, 10, 37, 45, 46, 47, 48…”

MnS Incorporation into Higher Manganese Silicide Yields a Green Thermoelectric Composite with High Performance/Price Ratio

“…By contrast, among all mid‐temperature TE materials, higher manganese silicide (HMS) is known as a naturally abundant, eco‐friendly, and low‐cost TE semiconductor with satisfactory thermal stability and good mechanical strength. The optimal power factor (PF = S 2 σ) of pure HMS is about 1.5 × 10 −3 W m −1 K −2 ; this value is higher than that of SnSe single crystal,11, 12 In‐doped Cu 2 Se ( ZT = 2.6)13 and even comparable to those of PbTe 0.7 S 0.3 14 or Ge 0.87 Pb 0.13 Te15 alloys, the ZT values of which exceed 2.0 after certain modifications.…”

“…In general, TE performance can be estimated via the dimensionless figure of merit ZT = S 2 σT /κ tot , where S , σ, T , and κ tot are the Seebeck coefficient, electrical conductivity, absolute temperature, and total thermal conductivity, respectively 5, 6, 7, 8. At present, PbTe‐based compounds9, 10 and SnSe single crystals11, 12 are identified as two typically efficient TE materials at medium temperature, with ZT max reaching high values of 2.2 and 2.6, respectively. However, several intrinsic tasks, such as the utilization of the toxic Pb element, complicate preparation processes, and poor thermal or chemical stabilities are expected to be difficult to overcome.…”