Surprisingly high in-plane thermoelectric performance in a-axis-oriented epitaxial SnSe thin films

Hou, Shuaihang; Li, Zhiliang; Xue, Yuli; Ning, Xinkun; Wang, Jianglong; Wang, Shufang

doi:10.1016/j.mtphys.2021.100399

Cited by 22 publications

(20 citation statements)

References 51 publications

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“…Typically, defects can be classified according to their dimensions: 0D point defects, 1D linear defects, 2D planar defects, and 3D body defects. As mentioned in the Introduction section, the scattering rates of defects are frequency dependent 22,25,64,159,160 . The strength of scattering and the resulting reduction in κ lat depend on the type and density of crystal defects.…”

Section: Extrinsic Sources For Slowing Down the Heat Transportmentioning

confidence: 94%

Slowing down the heat in thermoelectrics

Qin

Wang

Zhao

2021

InfoMat

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Heat transport has various applications in solid materials. In particular, the thermoelectric technology provides an alternative approach to traditional methods for waste heat recovery and solid‐state refrigeration by enabling direct and reversible conversion between heat and electricity. For enhancing the thermoelectric performance of the materials, attempts must be made to slow down the heat transport by minimizing their thermal conductivity (κ). In this study, a continuously developing heat transport model is reviewed first. Theoretical models for predicting the lattice thermal conductivity (κlat) of materials are summarized, which are significant for the rapid screening of thermoelectric materials with low κlat. Moreover, typical strategies, including the introduction of extrinsic phonon scattering centers with multidimensions and internal physical mechanisms of materials with intrinsically low κlat, for slowing down the heat transport are outlined. Extrinsic defect centers with multidimensions substantially scatter various‐frequency phonons; the intrinsically low κlat in materials with various crystal structures can be attributed to the strong anharmonicity resulting from weak chemical bonding, resonant bonding, low‐lying optical modes, liquid‐like sublattices, off‐center atoms, and complex crystal structures. This review provides an overall understanding of heat transport in thermoelectric materials and proposes effective approaches for slowing down the heat transport to depress κlat for the enhancement of thermoelectric performance.

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Section: Extrinsic Sources For Slowing Down the Heat Transportmentioning

confidence: 94%

Slowing down the heat in thermoelectrics

Qin

Wang

Zhao

2021

InfoMat

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“…The value is much lower than that of the SnSe thin film and single-crystalline SnSe bulk. [6,29,49,50] To further investigated the phonon scattering mechanisms in these MQWs, we studied the thermal conductivity using a series resistor model according to…”

Section: Resultsmentioning

confidence: 99%

“…The κ along the direction perpendicular to aaxis can be estimate when in-plane κ in the film has the same tendency and ratio as the b-axis κ in single-crystalline bulk. [6,56] As a matter of fact, the κ // of our MQWs could be estimated by SnSe single crystal due to the fact that the contribution of PbSe is less than 10%. Featured with high PF and low thermal conductivity, ZT at room temperature is significantly increased from 0.14 for PbSe single layer to 1.6 for [(PbSe) 3 /SnSe] 15 MQW.…”

Section: Resultsmentioning

confidence: 99%

“…Thermoelectric (TE) systems which can directly convert heat energy to electrical power have attracted extensive attention in recent years because of its great potential for recovering waste heat. [1][2][3][4][5][6][7][8] The efficiency of a TE material can be determined by a dimensionless figure of merit, ZT, defined as ZT = S 2 σ/κ, where S, σ, and κ are the Seebeck coefficient, the electrical conductivity, and the thermal conductivity, respectively. Therefore, an abundance of efforts are devoted to increase the ZT value of TE materials through reducing the resistivity, increasing the Seebeck coefficient and decreasing the thermal conductivity.…”

Section: Introductionmentioning

confidence: 99%

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Ultrahigh Power Factor and Ultralow Thermal Conductivity at Room Temperature in PbSe/SnSe Superlattice: Role of Quantum‐Well Effect

Zuo-ning

Ning

Jia

et al. 2021

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As experimentally shown by Hicks and Dresselhaus [16] the value of S is about 2.5 times than that of the bulk through quantum confinement effects by using QW structures. In 2007, Ohta et al. [17] observed a large Seebeck coefficient S = 850 µV K −1 in SrTiO 3 (barrier)/ SrTi 0.8 Nb 0.2 O 3 (well)/SrTiO 3 (barrier) multiple QW (MQW). By analyzing the optical spectra, Choi et al. found that the polaron plays an important role in determining the electronic structure in this MQW. [18] Through orbital reconstruction, recently Geisler et al. [19] also obtained large positive S (≈135 µV K −1 ) in LaNiO 3 /SrTiO 3 MQW at room temperature. As a matter of fact, for oxide or semiconductor MQW structure, the carrier electrons should be confined inside of a thin conducting layer. [16,17] There is valid argument for the attention that this will modified the electronic structure near Fermi level through polaron dimensional effect or quantum confinement effect. [18,20] In addition to high S, another strongly desired characteristic for TE materials is electrical and thermal conductivity, which will allow us to explore the high figures of merit. Venkatasubramanian et al. [21] reported that figure of merit can be further increased by controlling the transport of electrons in Bi 2 Te 3 / Sb 2 Te 3 superlattices. In addition, recently theoretical analyses for WS 2 /WSe 2 suplattices suggest that the ZT values can be enhanced by optimal the thermal conductivity. [22,23] However, for the earlier work of the semiconductor QW structure, the band offset is small and which most likely minimal the anisotropy between in-plane and out-of-plane electrical conductivities. [21,[24][25][26] Under this circumstance, due to the electron tunneling and thermal currents between the layers with these infinite potential barriers heights, the enhancement of the ZT values are rather moderate. On the other hand, for the oxide QW, although the tunneling effect are disappeared, but the thermal conductivity are 1-2 orders of magnitude higher than the semiconductor, [27,28] which limits their application in thermoelectric device.In this paper, we select the PbSe and SnSe as the constituent materials for the MQW structure to enhance Seebeck coefficient and optimal thermoelectric properties. PbSe has excellent thermoelectric properties in the mid-temperature region, along with low lattice thermal conductivity and small forbidden band width (≈0.28 eV). In this heterojunction system, SnSe was chosen as the potential barrier layer because on the one Reduced dimension is one of the effective strategies to modulate thermoelectric properties. In this work, n-type PbSe/SnSe superlattices with quantum-well (QW) structure are fabricated by pulsed laser deposition. Here, it is demonstrated that the PbSe/SnSe multiple QW (MQW) shows a high power factor of ≈25.7 µW cm −1 K −2 at 300 K, four times larger than that of PbSe single layers. In addition, thermal conductivity falls below 0.32 ± 0.06 W m −1 K −1 due to the phonon scattering at interface when the PbSe well thickness...

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“…Polycrystalline SnSe can be prepared by several synthesis techniques [58], among them with co-doping and multi-nanoprecipitates [59], with aqueous synthesis [60], as well as arc-melting. SnSe films can also show good thermoelectric performance [61][62][63]. Successful thermoelectric generators have been made based on SnSe very recently [64].…”

Section: Introductionmentioning

confidence: 99%

SnSe:Kx intermetallic thermoelectric polycrystals prepared by arc-melting

et al. 2022

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Neutron powder diffraction and thermoelectric characterization of SnSe:Kx intermetallic alloys are presented. Nanostructured ingots were prepared by arc-melting elemental tin and selenium along with potassium hydride. Up to x = 0.1 of K can be incorporated into SnSe. Rietveld refinement of the diffractograms locates potassium on the Sn site in the high-temperature Cmcm structure. However, in the low-temperature Pnma structure, K cannot be localized by difference Fourier maps, indicating the incorporation of K in a disordered form in the interlayer space. STEM-EELS indicates the incorporation of K into the SnSe grains. The resistivity upon K-doping at intermediate temperatures decreases by 1–2 orders of magnitude, but at high temperature is higher than the undoped SnSe. The Seebeck coefficient of K-doped SnSe remains p-type and almost temperature independent (400 μV/K for x = 0.1). The ultralow thermal conductivity of undoped SnSe decreases further upon K-doping to below 0.3 W/m K.

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Surprisingly high in-plane thermoelectric performance in a-axis-oriented epitaxial SnSe thin films

Cited by 22 publications

References 51 publications

Slowing down the heat in thermoelectrics

Slowing down the heat in thermoelectrics

Ultrahigh Power Factor and Ultralow Thermal Conductivity at Room Temperature in PbSe/SnSe Superlattice: Role of Quantum‐Well Effect

SnSe:Kx intermetallic thermoelectric polycrystals prepared by arc-melting

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