Enhancement of Thermoelectric Performance in CuSbSe₂ Nanoplate‐Based Pellets by Texture Engineering and Carrier Concentration Optimization

Abstract

generation efficiency, which is characterized by a dimensionless figure-of-merit ZT of the materials employed. ZT is defined as ZT = S 2 σT/(κ e +κ L ), where S, σ, and T are the Seebeck coefficient, electrical conductivity, and absolute temperature, κ e and κ L are thermal conductivity contributed by charge carriers (either electrons or holes) and phonons, respectively. [2] The thermoelectric properties of chalcogenides with weakly bonded 2D atomic sheets, such as SnSe, [3] SnSe 2 , [4] Cr 2 Ge 2 Te 6 , [5] GeSe, [6] and In 4 Se 3[7] are attracting attention because they show intrinsically low thermal conductivities deriving from the layered structure. CuSbSe 2 is also a similar chalcogenide with a direct bandgap of ≈1.0 eV [8,9] and exhibits potential for thin-film photovoltaic applications. [10,11] As shown in Figure 1a, the CuSbSe 2 crystallizes in an orthorhombic structure with the Pnma space group. This material has 2D double-layered honeycomb-like sheets within the ab plane, which is composed of self-condensed Sb 2 CuSe 3 and SbCu 2 Se 3 six-membered rings. [8] The Cu atom is tetrahedrally coordinated to four Se atoms with three kinds of CuSe bonds, while the Sb atom is coordinated by three Se atoms in a trigonal pyramidal configuration( Figure 1b). The Sb 3+ has lone-pair 5s 2 electrons which are stereochemically expressed in the structure. [12] Such structural features result in giant lattice vibration anharmonicity with a large average Grüneisen parameter γ ave of 1.215, [13,14] which is benifical for low thermal conductivity as found in tetrahedrites, [15,16] AgBiSe 2 , [17,18] CuSbS 2 , [19] and InTe [20] compounds. In addition, the neighboring 2D CuSbSe 2 sheets are interconnected by weaker secondary SbCu and SbSe bonds (pink dotted lines in Figure 1b). [21] The lattice vibration anharmonicity combined with the interlayer weaker bonding leads to low lattice thermal conductivity in the CuSbSe 2 compound, [22] similar to SnSe, [23] AgSbTe 2 , [24] and Cu 3 SbSe 3 . [25] In addition, first-principles density functional theory calculations reveal that the valence bands near the Fermi level of CuSbSe 2 are relatively flat and degenerate at Z point (0, 0, 1/2), which lead to a high effective mass (m*≈ 2.05 m 0 ). [9] Thus, an intrinsically high Seebeck coefficient is also expected in this compound. These attributes as well as the earth-abundant and low-toxic constituent elements make this material worth exploring for This work reports the thermoelectric properties of the CuSbSe 2 -x mol% PtTe 2 (x = 0, 0.5, 1.0, 1.5, and 2.0) pellets composed of highly oriented single crystalline nanoplates. CuSbSe 2 -PtTe 2 single crystalline nanoplates are prepared by a wet-chemical process, and the pellets are prepared through a bottom-up self-assembly of the CuSbSe 2 -PtTe 2 nanoplates and spark plasma sintering (SPS) process. X-ray diffraction and field emission scanning electron microscopic analyses show a highly textured nature with an orientation factor of ≈0.8 for (00l) facets along the primary surface of the p...

Synergistical Tuning Interface Barrier and Phonon Propagation in Au–Sb2Te3 Nanoplate for Boosting Thermoelectric Performance

“…Designing low-dimensional materials has been proven to be an effective strategy to control the three thermoelectric parameters independently, obtaining factorial improvement in ZT. − Dimensionality plays a significant role in manipulating propagation of charge carriers and phonons, introducing quantum confinement effect on electronic density of states, electronic bands, phonon group velocity, and interface scattering, therefore synergistically optimizing the electronic property and thermal property. For instance, 2-dimensional (2D) layered chalcogenide nanomaterials are demonstrated to exhibit a high power factor due to the unique quantum effect and ultralow thermal conductivity originating from the enhanced boundary scattering. − 0-dimensional (0D) quantum dots help to form a quantum well, achieving an electron transmitting–phonon blocking region to boost the thermoelectric figure-of-merit. − …”

Enhanced Thermoelectric Performance and Mechanical Property in Layered Chalcostibite CuSb1–xPbxSe2

“…Figure b compares the zT of CuSbSe 2 and CuSb 0.90 Pb 0.10 Se 2 with the previously reported CuSbSe 2 -based materials, − ,, where the composition of CuSb 0.90 Pb 0.10 Se 2 shows higher values when compared to the reports, ,, which can be further improved by choice of suitable dopant to bring it as an efficient thermoelectric material for intermediate temperature. The thermoelectric parameter of the carrier concentration ( n p ), electrical conductivity (σ), Seebeck coefficient ( S ), total thermal conductivity (κ total ), and thermoelectric figure of merit ( zT ) of all the samples are summarized in Table .…”

Thermoelectric Performance of the 2D Bi2Si2Te6 Semiconductor

“…The thermoelectric energy conversion technology is of importance in increasing energy efficiency as it allows the direct conversion of heat energy to electricity, − thus lots of thermoelectric generator prototypes have been developed using bismuth antimony telluride, GeTe, PbTe, half-Heuslers, silicides, SnSe, and so on in recent years. − To generate power efficiently from heat, it is desirable that the thermoelectric materials employed in generators have a high dimensionless figure of merit (ZT), expressed as ZT = S 2 σ T /κ, where S is the Seebeck coefficient, σ is the electrical conductivity, T is the absolute temperature, and κ is the thermal conductivity ( S 2 σ is referred to as the power factor). − High energy conversion efficiency requires high ZT, which in turn requires either high S 2 σ or low κ . Therefore, to achieve high thermoelectric performance, ongoing efforts in thermoelectric research are focused on the exploration of materials with intrinsically low thermal conductivity, such as Mg 3 Sb 2 , SnSe 2 , BiCuSeO, Cu 12 Sb 4 S 13 , Cu 2 S, AgCuTe, SnSe, − AgGaTe 2 , CuSbSe 2 , , and AgSbTe 2 . Interestingly, many of these compounds have a 2D layered crystal structure with anharmonic and weak interlayer chemical bonding (e.g., van der Waals bonding) …”

“…10−16 High energy conversion efficiency requires high ZT, which in turn requires either high S 2 σ or low κ. 17 Therefore, to achieve high thermoelectric performance, ongoing efforts in thermoelectric research are focused on the exploration of materials with intrinsically low thermal conductivity, 18 such as Mg 3 Sb 2 , 19 SnSe 2 , 20 BiCuSeO, 21 Cu 12 Sb 4 S 13 , 22 Cu 2 S, 23 AgCuTe, 24 SnSe, 25−29 AgGaTe 2 , 30 CuSbSe 2 , 31,32 and AgSbTe 2 . 1 Interestingly, many of these compounds have a 2D layered crystal structure with anharmonic and weak interlayer chemical bonding (e.g., van der Waals bonding).…”