Author(s) Ma, N.; Li, Y.Y.; Chen, L.; Wu, L.M.
Journal J Am Chem Soc
Date Published 2020 Mar 10

The discovery of low-cost, less toxic, and earth-abundant thermoelectric materials is a great challenge. Herein, with the aid of a unique and safe boron-chalcogen method, we discover the new tetragonal α-CsCuSe, featuring a previously unrecognized structure in the ternary family of Cs/Cu/Se. The structure is constructed by a Chinese-knot-like CuSe building unit that is further linked into a 3D network. α-CsCuSe exhibits thermal stability that is superior to that of the recently established thermoelectric materials CuSe and CsAgTe suffering unfavorable phase transitions. Distinct from the liquidlike migration in CuSe, α-CsCuSe obeys a typical crystalline solid thermal transport behavior dominated by Umklapp scattering. In compariosn to the isostructural CsAgTe, α-CsCuSe shows a 30% volume decrease that leads to stronger orbital overlapping that markedly decreases the band effective mass (*). With a smaller * and a softer Cu-Se bond, α-CsCuSe eventually realizes a 200% increase in the power factor (8.17 μW/(cm K), the highest among the copper-rich alkali-metal chalcogenides) and a figure of merit (ZT) of 1.03 at 980 K. Further, the doping in α-Cs(CuSb)Se boosts the lattice anharmonicity by the lone pairs that, via intensifying the Umklapp scattering and slowing the phonon velocity, ensures a low lattice thermal conductivity (0.40 W/(m K)), and finally leads to a ZT value of 1.30 at 980 K. Our discovery represents a step toward low-cost, earth-abundant, and high-performance chalcogenide materials that will shed useful light on future exploration in the related fields.

DOI 10.1021/jacs.0c00062
ISSN 1520-5126
Citation J Am Chem Soc. 2020.

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