Reduction In Lattice Thermal Conductivity Research Articles

Reduced lattice thermal conductivity through tailoring of the crystallization behavior of NbCoSn by V addition

Nanostructuring is a key approach for reducing lattice thermal conductivity. Amorphous precursors can be used to obtain complex nanostructures, as their crystallization behavior can be controlled by varying their composition, temperature, and annealing time. Herein, we investigated the effects of V alloying on the crystallization behavior and resulting lattice thermal conductivity of amorphous NbCoSn alloys. After heat treatment at 783 K for 2 h, the V-containing alloy showed a significantly finer grain size (100 ± 30 nm) than the alloy without V (870 ± 360 nm) owing to the different crystallization kinetics. We revealed that Sn-rich nanoprecipitates with a diameter of 10 nm acted as heterogeneous nucleation sites for crystallization, resulting in a finer grain size in the V-containing alloy. As a result, the V-containing alloy exhibited a lower lattice thermal conductivity (2.6 ± 0.2 W m−1 K−1) than the alloy without V (3.3 ± 0.2 W m−1 K−1) at room temperature owing to increased phonon scattering at the grain boundary, point defects, and nanoprecipitates.

Alloy-induced reduction and anisotropy change of lattice thermal conductivity in Ruddlesden–Popper phase halide perovskites

Alloy-induced reduction and anisotropy change of lattice thermal conductivity in Ruddlesden–Popper phase halide perovskites

Defect Chemistry Engineering Promotes the Dopability of Cu for an Extraordinary Thermoelectric Performance of Hole-Doped PbSe with Resonant States

Cu substitution for Pb (CuPb) has been theoretically predicted to introduce resonant states near the valence band edge of PbSe. However, experimentally, it has not been verified yet due to the extremely low solubility (∼0.3 atom %) of CuPb. In this study, we demonstrate that the solubility limit of CuPb is extended to at least 1.5 atom % in PbSe by pairing with an identical amount of Cu interstitials (Cui), while excess Cu precipitates out as a Cu2Se phase at grain boundaries. As a result of the increased dopability of CuPb, a significant enhancement of the Seebeck coefficient is realized in hole-doped PbSe because of CuPb-induced resonant states. This is also testified by first-principles calculations. Moreover, the rich point defects (CuPb, Cui), line defects (dislocations), and Cu2Se precipitates remarkably frustrate the phonon propagation of PbSe, leading to ∼45% reduction of lattice thermal conductivity (κlat) at room temperature. At elevated temperatures (>623 K), there is a dynamic migration of Cu atoms from Cu2Se precipitates to tetrahedral interstices of the PbSe matrix as evidenced by the temperature-variant Hall study and thermal expansion coefficient measurement. This diffusion-like process of Cu further drops the κlat to ∼0.27 W m–1 K–1 at 823 K. Consequently, a peak ZT of ∼1.8 at 873 K is achieved in the (Cui)0.01Pb0.97(CuPb)0.01Na0.02Se sample. This work highlights the potential of the defect structure design in innovating new functional materials, particularly high-performance thermoelectrics.

Enhancing thermoelectric performance of n-type Bi2Te2.7Se0.3 through the incorporation of MnSb2Se4 nanoinclusions

Bi2Te3-based alloys are the state of art thermoelectric materials for near-room temperature applications. However, the figure of merit, ZT, of n-type Bi2Te2.7Se0.3 (BTS) is not large enough to its wide applications, and previous studies seldom involve incorporation of Mn-based alloys in BTS-based composites. Here, we show that through dispersion of transition-metal selenide MnSb2Se4 (MSS) into BTS can simultaneously increase the power factor (PF) and reduce lattice thermal conductivity (κL) greatly. Experimental evidences show that increased PF comes from enhanced thermopower due to energy filtering effect; while the reduced κL originates mainly from intensified phonon scattering by the MSS nanoinclusion and dislocations. As a result, a large ZTmax = 1.23 (at 345 K) and an average ZTave ∼ 1.15 (300 K-473 K) are achieved for BTS/0.50 wt% MSS sample, which is respectively ∼ 48% and ∼ 42% larger than those of pristine BTS. In addition, this sample shows better mechanical properties with its Vickers hardness being increased by 17%. Present results demonstrate that incorporation of transition-metal selenides, such as MSS, is a promising way to improving thermoelectric performance as well as mechanical properties of BTS.

Anomalous lattice thermal conductivity driven by all-scale electron-phonon scattering in bulk semiconductors

Electron-phonon coupling (EPC) has been broadly considered to govern the charge transport in solids, whereas its effect on thermal conductivity, especially for semiconductors at ambient temperatures, is a widely debated issue in condensed-matter physics. Employing state-of-the-art first-principles calculations to quantify all the possible scattering factors, we show the dominant role of EPC in phonon transport of $n$-doped GaSb, which yields an unprecedented reduction of lattice thermal conductivity and triggers anomalous temperature-independent behavior. The significant EPC impact hinges on the joint effect of multiple conduction pockets, large EPC strength, and bunched heat-carrying acoustic branches, provoking strong electron-phonon scattering to surpass the intrinsic phonon-phonon scattering for all-scale phonons, in contrast to the case in silicon that only long-wave phonons can be scattered by carriers even at high doping level. This work advances the understating of phonon transport in doped semiconductors and stimulates potential heat management application of anomalous thermal conductivity.

Hydride Anion Substitution Boosts Thermoelectric Performance of Polycrystalline SrTiO3 via Simultaneous Realization of Reduced Thermal Conductivity and High Electronic Conductivity

AbstractThe development of environmentally benign thermoelectric materials with high energy conversion efficiency (ZT) continues to be a long‐standing challenge. So far, high ZT has been achieved using heavy elements to reduce lattice thermal conductivity (κlat). However, it is not preferred to use such elements because of their environmental load and high material cost. Here a new approach utilizing hydride anion (H−) substitution to oxide ion is proposed for ZT enhancement in thermoelectric oxide SrTiO3 bulk polycrystals. Light element H− substitution largely reduces κlat from 8.2 W/(mK) of SrTiO3 to 3.5 W/(mK) for SrTiO3−xHx with x = 0.216. The mass difference effect on phonon scattering is small in the SrTiO3−xHx, while local structure distortion arising from the distributed Ti−(O,H) bond lengths strongly enhances phonon scattering. The polycrystalline SrTiO3−xHx shows high electronic conductivity comparable to La‐doped SrTiO3 single crystal because the H− substitution does not form a grain boundary potential barrier and thus suppresses electron scattering. As a consequence, SrTiO3−xHx bulk exhibits maximum ZT = 0.11 at room temperature and the ZT value increases continuously up to 0.22 at T = 657 K. The H− substitution idea offers a new approach for ZT enhancement in thermoelectric materials without utilizing heavy elements.

Inhibiting the bipolar effect via band gap engineering to improve the thermoelectric performance in n-type Bi2-Sb Te3 for solid-state refrigeration

• Se replacement can enlarge the E g and thus effectively mitigate the bipolar effect. • The manipulation of donor-like effect retains the optimized carrier concentration. • The large strain field and mass fluctuation reduce lattice thermal conductivity. • A state-of-the-art zT = 1.0 at 300 K is attained for n -type Bi 1.5 Sb 0.5 Te 2.8 Se 0.2 . • n -type Bi 2- x Sb x Te 3 becomes a promising candidate for solid-state cooling field. To date, the benchmark Bi 2 Te 3 -based alloys are still the only commercial material system used for thermoelectric solid-state refrigeration. Nonetheless, the conspicuous performance imbalance between the p -type Bi 2- x Sb x Te 3 and n -type Bi 2 Te 3- x Se x legs has become a major obstacle for the improvement of cooling devices to achieve higher efficiency. In our previous study, novel n -type Bi 2- x Sb x Te 3 alloy has been proposed via manipulating donor-like effect as an alternative to mainstream n -type Bi 2 Te 3- x Se x . However, the narrow bandgap of Bi 2- x Sb x Te 3 provoked severe bipolar effect that constrained the further improvement of zT near room temperature. Herein, we have implemented band gap engineering in n -type Bi 1.5 Sb 0.5 Te 3 by employing isovalent Se substitution to inhibit the undesired intrinsic excitation and achieve the distinguished room-temperature zT . First, the preferential occupancy of Se at Te 2 site appropriately enlarges the band gap, thereby concurrently improving the Seebeck coefficient and depressing the bipolar thermal conductivity. In addition, the Se alloying mildly suppresses the compensation mechanism and essentially preserves the already optimized carrier concentration, which maintains the peak zT near room temperature. Moreover, the large strain field and mass fluctuation generated by Se alloying leads to the remarkable reduction of lattice thermal conductivity. Accordingly, the zT value of Bi 1.5 Sb 0.5 Te 2.8 Se 0.2 reaches 1.0 at 300 K and peaks 1.1 at 360 K, which surpasses that of most well-known room-temperature n -type thermoelectric materials. These results pave the way for n -type Bi 2- x Sb x Te 3 alloys to become a new and promising top candidate for large-scale solid-state cooling applications.

Contradicting Influence of Zn Alloying on Electronic and Thermal Properties of a YbCd2 Sb2 -Based Zintl Phase at 700 K.

Zintl compounds are promising thermoelectric materials for power generation as their electronic and thermal transport properties can be simultaneously engineered with anion/cation alloying. Recently, a peak thermoelectric figure-of-merit, zT, of 1.4 was achieved in a (Yb0.9 Mg0.1 )Cd1.2 Mg0.4 Zn0.4 Sb2 Zintl phase at 700 K. Although the effects of alloying Zn in lattice thermal conductivity had been studied thoroughly, how the Zn alloying affects its electronic transport properties has not yet been fully investigated. This study evaluates how the Zn alloying at Cd sites alters the band parameters of (Yb0.9 Mg0.1 )Cd1.6-x Mg0.4 Znx Sb2 (x=0-0.6) using the Single Parabolic Band model at 700 K. The Zn alloying increased the density-of-states effective mass (md * ) from 0.87 to 0.97 m0 . Among Zn-alloyed samples, the md * of the x=0.4 sample was the lowest (0.93 m0 ). The Zn alloying decreased the non-degenerate mobility (μ0 ) from 71 to 57 cm2 s-1 V-1 . Regardless of Zn alloying content, the μ0 of the Zn-alloyed samples were similar (∼57 cm2 s-1 V-1 ). Consequently, the x=0.4 with the highest zT exhibited the lowest weighted mobility (μW ). The lowest μW represents the lowest theoretical electronic transport properties among other x. The highest zT at x=0.4 despite the lowest μW was explained with a significant lattice thermal conductivity reduction achieved with Zn alloying with x=0.4, which outweighed the deteriorated electronic transport properties also due to the alloying.

Ag Interstitial Inhibition and Phonon Scattering at the ZnSe Nano-Precipitates to Enhance the Thermoelectric Performance of Ag2Se

Ag2Se-based thermoelectric (TE) materials have attracted significant attention recently due to their potential application near room temperature. Manipulating the stoichiometric ratio of Ag/Se and anion doping are usually used as effective approaches to enhance the TE properties. Here, we report a strategy to simultaneously enhance the power factor (PF) and reduce the thermal conductivity of Ag2Se by introducing ZnSe nano-precipitates. The excessive carrier concentration in the intrinsic Ag2Se is successfully reduced by the Ag interstitial inhibition due to the introduction of secondary-phase ZnSe nano-precipitates, thereby enhancing the PF up to a maximum value of ∼22.2 μW m–1 K–2 at 383 K and decreasing the electronic thermal conductivity from ∼1.2 to ∼0.8 W m–1 K–1 at 383 K. In addition, the phonon scattering at ZnSe nano-precipitates contributes to the reduction of lattice thermal conductivity from ∼0.5 to ∼0.4 W m–1 K–1 at 383 K. As a result, a high peak zT of ∼0.7 at 383 K and an average zT of 0.6 at 313–383 K are obtained in the sample Ag2Se-0.005ZnSe, which is one of the highest values amongst Ag2Se-based TE materials. This study could provide guidance to improve the TE properties of materials similar to Ag2Se.

Unraveling the structural details and thermoelectric transports of 2D-3D hetero-structure composites

With in-depth research on the thermoelectric properties of the single-phase traditional three-dimensional (3D) and emerging two-dimensional (2D) materials, there is a deficit in the study of the 2D-3D hetero-structure phases, whose structural details and transport features still require a clear understanding. In this work, taking 2D-SnSe and 3D-PbSe as research objects, we prepared mixture-phase composites with the coexistence of 2D and 3D phases and studied the relationship between the thermoelectric transports and phase structures. By conducting the powder X-ray diffraction measurements and Rietveld refinements, we obtained the dynamic 2D-3D hetero-structure compositions of weight percentages with heating-cooling cycles. Subsequently, we estimated the lattice thermal conductivity from the experimental measurements and theoretical calculations as functions of 2D-3D compositions. We discovered that the lattice thermal conductivity reduction became more obvious in the samples with small amounts of hetero-structure phases, benefiting from the extra scattering of phonons by the higher density of hetero-structure interfaces. Moreover, we observed the 2D-3D hetero-structures at the microscopic scale by HADDF-STEM, experimentally confirming the presence of low symmetrical-PbSe and high symmetrical-SnSe phases. This study gave a perspective and investigation method to unravel both the structural details and transport properties of 2D-3D hetero-structure composites, which might provide new strategies for optimizing thermoelectric performance by depressing the thermal transports in hetero-structure materials.

High‐Temperature Thermoelectricity in Narrow‐Gap Semiconductor SmS with Strong Electron‐Hole Asymmetry

AbstractHigh‐temperature thermoelectric (TE) materials are common wide‐gap semiconductors that are used in order to prevent the bipolar effect. Here, a potential high‐temperature n‐type TE material SmS with a simple NaCl structure that demonstrates a narrow band gap of ≈0.25 eV is reported. As expected, a temperature‐dependent carrier concertation is observed, which is attributed to the thermal activation of electrons from valence band edge to conduction band. Interestingly, the intrinsic activation does not cause any sign of a bipolar effect. Density functional theory calculations suggest that the phenomenon originates from the strong electron‐hole asymmetry in the electronic structure and the electron‐to‐hole conductivity ratio is as high as 700–900. As a result, the activated minority carriers barely participate in the TE transport and the maximum power factor reaches 1.41 mW K−2 m−1 at 1123 K. By further alloying with Se to reduce lattice thermal conductivity, a peak zT of ≈1.1 is obtained in Sm1.08S0.78Se0.22 at 1123 K, which is among the best n‐type high‐temperature thermoelectrics. This study proves high‐temperature TE materials can be found in narrow‐gap semiconductors, which significantly enriches the scope of possibilities for novel TE materials.

Electrical property enhancement and lattice thermal conductivity reduction of n-type Mg3Sb1.5Bi0.5-based Zintl compound by In&Se co-doping

Mg3Sb1.5Bi0.5-based Zintl compounds have attracted extensive attention as potential thermoelectric materials due to their earth-abundant elements. However, pure and intrinsic Mg3Sb1.5Bi0.5 manifests a poor thermoelectric performance because of its low electrical conductivity of about 3 × 102 S/m at room temperature. In this work, In and Se co-doping was carried out to optimize the thermoelectric performance of n-type Mg3Sb1.5Bi0.5-based material. The experimental results revealed that the carrier concentration and mobility of Mg3Sb1.5Bi0.5 significantly increased after In and Se co-doping, leading to an improvement of power factor. Simultaneously, lattice thermal conductivity was significantly reduced due to the large mass difference between In and Mg. A maximum zT of 1.64 at 723 K was obtained for the Mg3.17In0.03Sb1.5Bi0.49Se0.01 sample. And an average zT value of about 1.1 between 300 and 723 K was achieved, which insures its possible application at medium temperature range as a non-toxic and low-cost TE material.

Revealing the decisive factors of the lattice thermal conductivity reduction by electron-phonon interactions in half-Heusler semiconductors

The role of electron-phonon (EP) scattering in lattice thermal conductivity (κL) of thermoelectric material has not been fully studied until now, especially for the decisive factors that influence the reduction of κL. To address this issue, we report the effect of EP interactions on κL at a series of temperatures and carrier concentrations for 18 half-Heusler compounds. Among all the compounds investigated, the hole-doped TiCoSb and the electron-doped ZrIrSb have the largest κL reductions (32% & 20%) by EP interactions at 300 K, under the carrier concentration of 1021 cm−3. Detailed analyses reveal that the system with strong EP coupling strength and high electronic density of states at the Fermi level (N (EF)) favor the κL reduction, because these two factors are beneficial for EP scattering rates. And a high N (EF) can be caused by a high carrier concentration and/or a large effective mass. Temperature is another factor that affects the reduction of κL by EP interactions due to its imbalance influence on EP and phonon-phonon (PP) scatterings. Furthermore, after considering the influences from the aliovalent doping and grain boundary, the EP interactions still play a non-negligible role on κL reduction, especially at low temperatures and high carrier concentrations. Our work provides a complete picture for understanding the mechanism of EP interactions in material's thermal transport.

Realization of an ultra-low lattice thermal conductivity in Bi2AgxSe3 nanostructures for enhanced thermoelectric performance

Bismuth Selenide is a Tellurium free topological insulator in V-VI compounds with an excellent thermoelectric performance from room temperature to mid-temperature region. Herein, hydrothermally prepared polycrystalline Bi2AgxSe3 nanostructures have been reported for thermoelectric application. The crystal structure identification and morphology with the elemental presence were analyzed by XRD (X-ray diffraction), HR-SEM with EDS (High resolution scanning electron microscope with energy dispersive X-ray), and HR-TEM (High-resolution transmission electron microscope) measurements. The reduced lattice thermal conductivity and enhanced electrical transport properties synergistically boost the thermoelectric properties through the highly-dense stacking faults with the presence of dislocations. The IFFT (Inverse Fast Fourier Transform) pattern reveals the existence of stacking faults and dislocations. These highly dense stacking faults and dislocations act as active phonon scattering centers, which can contribute to effective phonon scattering resultsin extremely low lattice thermal conduction of 0.3 W/mK at 543 K. On the other hand, the involvement of phonon–phonon scattering primarily reduced the lattice thermal conductivity at elevated temperatures. In addition, phonon-carrier scattering was less compared to phonon–phonon scattering at elevated temperature region. Moreover, the enhancement of electrical conductivity and controlled reduction of the Seebeck coefficient plays a vital role in achieving the maximum power factor of 335 μW/mK2 at 543 K due to the energy filtering effect. The synergistic combination of low thermal conduction and the maximum power factor helps to achieve the high peak zT of 0.3 at 543 K.

Ultra-high power factor of p-type Bi2Se3 for room-temperature thermoelectric applications.

Achieving high zT in n-type and p-type thermoelements in similar compounds is a great challenge for device construction. Herein, we report a high-power factor of 480 μW/mK2 in Ga and Mn co-doped Bi2Se3 along with a maximum zT of 0.25 at 303 K as a p-type thermoelement. The co-doped Ga and Mn play distinct roles in enhancing the hole concentration to 1.6 × 1019 cm-3 with a maximized effective mass. In addition, a drastic reduction in lattice thermal conductivity of 0.5 W/mK is attained due to point defects of mass and strain field fluctuation scattering in Bi2Se3.

Effects of nano-SiO<sub>2</sub> on thermoelectric properties of Mg<sub>3</sub>Sb<sub>2</sub>-based materials

Recently, Mg<sub>3</sub>(Sb,Bi)<sub>2</sub>-based thermoelectric materials have received extensive attention owing to excellent thermoelectric properties and the low cost. This study investigates the change and mechanism of thermoelectric transport properties of Mg<sub>3.275</sub>Mn<sub>0.025</sub>Sb<sub>1.49</sub>Bi<sub>0.5</sub>Te<sub>0.01</sub>/SiO<sub>2</sub> nanocomposite. The results show that nano-SiO<sub>2</sub> can effectively scatter phonons, promote the reduction of lattice thermal conductivity, and optimize the heat transport performance owing to the introduction of a large number of tiny grain boundaries. For example, when SiO<sub>2</sub> content is 0.54%, the thermal conductivity decreases by 15% from 1.24 W/(m·K) to 1.04 W/(m·K) compared with that of 0% SiO<sub>2</sub> sample at room temperature. At the same time, the material system also has a strong scattering effect on electrons. This leads to a sharp attenuation of power factor and electrical transport performance with decline of mobility and conductivity in the room temperature area. Nano SiO<sub>2</sub> is an effective candidate for regulating thermoelectric properties of Mg<sub>3</sub>Sb<sub>2</sub> based thermoelectric material. The thermoelectric transport performance of the material will be improved by combining with other methods, such as appropriate grain boundary modification to reduce the potential barrier of charge carrier transport.

GaSb doping facilitates conduction band convergence and improves thermoelectric performance in n-type PbS

We improve n-type lead chalcogenides by adding GaSb to reduce lattice thermal conductivity and achieve conduction band convergence. This significantly enhances the thermoelectric performance of n-type PbS, making it comparable to its p-type counterpart.

Modulated Fermi Level and Relaxed Lattice Strain Leading to Enhanced Thermoelectric Properties in AgSbSe2

Cubic-phase AgSbSe2 has been known as a decent p-type thermoelectric material, due to its intrinsically low lattice thermal conductivity; nevertheless, the difficulty in modulating its electrical transport performance impeded its further competition with other state-of-the-art mid-temperature thermoelectrics. In this work, we investigated the effects of Pb doping and Sb vacancies on modulating the thermoelectric properties of AgSbSe2. Pb doping was found to be able to obviously increase the hole concentration, leading to a descending of Fermi level well into the multiple valence bands, thus leading to an enhanced band degeneracy; subsequent Sb vacancies could play the role of relaxing the local lattice strains due to PbSb substitution, resulting in a weakened charge carrier scattering and enhanced weighted mobility. Consequently, a peak power factor PFmax of 7.5 μW cm–1 K–2 at 523 K was achieved in the composition of AgSb0.935Pb0.06Se2, which is 40% higher than that of pristine AgSbSe2. Furthermore, Pb doping and Sb vacancies induce enhanced point defect scattering of high-frequency heat-carrying phonons, yielding a reduced lattice thermal conductivity and a remarkably enhanced maximal ZTmax value of 1.02 at 723 K in the sample AgSb0.935Pb0.06Se2.

Enhanced thermoelectric performance of polycrystalline InSb1−xBix by using isoelectronic substitution on the Sb site

InSb has superior electronic transport with low bandgap and high mobility of charge carriers, however, its high lattice thermal conductivity makes it less applicable for thermoelectric applications. Herein we report an effective approach to simultaneously enhance the power factor and reduce total thermal conductivity by isoelectronic doping of Bi for Sb. A series of polycrystalline InSb 1-x Bi x is prepared. The enhanced power factor is attributed to the increase of carrier concentration by charge transfer from the Bi d -orbital states to the In 4 d -orbital states based on analyses of both the Bi and In L 3 -edge XANES spectra of InSb 1−x Bi x . The reduced total thermal conductivity arises from the reduced lattice thermal conductivity due to the point defects. The strain field fluctuations are evidenced by the blue shift in Raman spectra of InSb 1- x Bi x . As a result, zT = 0.56 is attained at 700 K, which is 16% higher than the pristine InSb. • Isoelectronic Bi doped InSb prepared by melting in an evacuated-and-encapsulated ampoule followed by hot pressing. • Isoelectronic doping of Bi on Sb sites leads to a reduced bandgap and effective enhancement of σ and σS 2 . • Increased carrier concentration due to charge transfer from the Bi d-orbital states to In 4 d -orbital states. • T -0.5 dependence of lattice thermal conductivity showing strong alloy scattering. • Blue shift in Raman spectra indicating compressive strain field fluctuations.

Realizing high thermoelectric performance of Cu and Ce co-doped p-type polycrystalline SnSe via inducing nanoprecipitation arrays

Thermoelectric (TE) performance of polycrystalline stannous selenide (SnSe) has been remarkably promoted by the strategies of energy band, defect engineering, etc. However, due to the intrinsic insufficiencies of phonon scattering and carrier concentration, it is hard to simultaneously realize the regulations of electrical and thermal transport properties by one simple approach. Herein, we develop Cu and Ce co-doping strategy that can not only greatly reduce lattice thermal conductivity but also improve the electrical transport properties. In this strategy, the incorporated Cu and Ce atoms could induce high-density SnSe2 nanoprecipitation arrays on the surface of SnSe microplate, and produce dopant atom point defects and dislocations in its interior, which form multi-scale phonon scattering synergy, thereby presenting an ultralow thermal conductivity of 0.275 W·m-1·K-1 at 786 K. Meanwhile, density functional theory (DFT) calculations, carrier concentration, and mobility testing reveal that more extra hole carriers and lower conducting carrier scattering generate after Cu and Ce co-doping, thereby improving the electrical conductivity. The co-doped Sn0.98Cu0.01Ce0.01Se bulk exhibits an excellent ZT value up to ~1.2 at 786 K and a high average ZT value of 0.67 from 300 to 786 K. This work provides a simple and convenient strategy of enhancing the TE performance of polycrystalline SnSe.