Structural Modularization of Cu₂Te Leading to High Thermoelectric Performance near the Mott–Ioffe–Regel Limit

Abstract

emission, noiseless, friendliness for miniaturization, and reliability. [1,2] Based on the Seebeck and Peltier effects, thermoelectricity enables a direct energy conversion between temperature difference and electricity. [3] The performance of a TE material is primarily gauged by the material's figure of merit, zT = α 2 T/ρκ, where α is the Seebeck coefficient, T is the absolute temperature, ρ is the electrical resistivity, and κ is the total thermal conductivity (consisting of the lattice thermal conductivity κ L and the electronic thermal conductivity κ E ).In view of the adversely interdependent S, ρ, and κ, attaining high zT values entails hierarchical diverse structurefunctional modules in the material. To this end, "hybrid crystal" or "structural modularity" is preferred in TE materials research as these complex materials are composed of building modules with distinct compositions and functions, [4,5] through which the adverse coupling of S, ρ, and κ can be eased and tuned selectively. Layered cobalt oxides, [6] filled skutterudites, [7] meta-phases, [8] and liquid-like TE materials [9] are good examples To date, thermoelectric materials research stays focused on optimizing the material's band edge details and disfavors low mobility. Here, the paradigm is shifted from the band edge to the mobility edge, exploring high thermoelectricity near the border of band conduction and hopping. Through coalloying iodine and sulfur, the plain crystal structure is modularized of liquid-like thermoelectric material Cu 2 Te with mosaic nanograins and the highly size mismatched S/Te sublattice that chemically quenches the Cu sublattice and drives the electronic states from itinerant to localized. A state-of-the-art figure of merit of 1.4 is obtained at 850 K for Cu 2 (S 0.4 I 0.1 Te 0.5 ); and remarkably, it is achieved near the Mott-Ioffe-Regel limit unlike mainstream thermoelectric materials that are band conductors. Broadly, pairing structural modularization with the high performance near the Mott-Ioffe-Regel limit paves an important new path towards the rational design of high-performance thermoelectric materials.

Improved Thermoelectric Figure of Merit in Polyol Method-Prepared Cu1–xBixS (x ≤ 0.06) Nanosheets

“…Copper-based chalcogenides have shown quite good TE properties such as a ZT value of 2.0 at 1000 K for S-doped Cu 2 Se, 10 ZT of 2.3 at 1000 K for Cu 1.94 Se 0.5 S 0.5 11 and ZT of 1.4 at 850 K in Cu 2 Te 0.5 I 0.1 S 0.4 . 12 Sulfides of copper are one type of example of metal chalcogenides with chemical stability at room temperature having a wide range of stoichiometric compositions like Cu 2 S (chalcocite), Cu 1.96 S (djurleite), Cu 1.8 S (digenite), Cu 1.75 S (anilite), CuS (covellite), Cu 9 S 8 (yarrowite), and CuS 2 (villamaninite). 13 They are considered as superionic conductors.…”

Recent advances, challenges, and perspective of copper‐based liquid‐like thermoelectric chalcogenides: A review

“…(A) Carrier concentrations of Cu 2 Te 1− x I x , Cu 2 Te 0.9 −y I 0.1 S y , and Cu 2 Te 1 −y S y as a function of I and S. (B) Carrier motilities of Cu 2 Te 1− x I x , Cu 2 Te 0.9 −y I 0.1 S y , and Cu 2 Te 1 −y S y versus I and S along with the extended electronic states 218 . (C) ZTs of Cu 2 Te 1− x I x , Cu 2 Te 0.9 −y I 0.1 S y , and Cu 2 Te 1 −y S y versus Seebeck coefficient in comparison to the doped, composited and nanostructured Cu 2 Te 69,96,219 .…”

High Thermoelectric Performance in Cu2SnS3 by Control Over Phase‐Dependent Mobility Edge

“…So far, the influence of disorder extent on TE performance is still controversial. In single-phase system, for instance, Biswas et al suppressed the atomic disorder by Cd doping in polycrystalline AgSbTe 2 to promote carrier mobility and achieved a record high zT of 2.6 at 573 K. [16] Shi et al facilitated the disorder in Cu 2 Te by I and S co-alloying and obtained a high zT value of 1.4 at 850 K. [17] In general, disorder extent is not only closely related to lattice thermal conductivity but also to the mobility edge value, which determines the electrical transport property of disordered systems. [16] It is therefore speculated that the TE properties of composites can also be tuned by control the ratio of phases with different disorder extent related to mobility edge.…”