Copper chalcogenide thermoelectric materials

Abstract

Cu-based chalcogenides have received increasing attention as promising thermoelectric materials due to their high efficiency, tunable transport properties, high elemental abundance and low toxicity. In this review, we summarize the recent research progress on this large family compounds covering diamond-like chalcogenides and liquid-like Cu 2 X (X=S, Se, Te) binary compounds as well as their multinary derivatives. These materials have the general features of two sublattices to decouple electron and phonon transport properties. On the one hand, the complex crystal structure and the disordered or even liquid-like sublattice bring about an intrinsically low lattice thermal conductivity. On the other hand, the rigid sublattice constitutes the charge-transport network, maintaining a decent electrical performance. For specific material systems, we demonstrate their unique structural features and outline the structure-performance correlation. Various design strategies including doping, alloying, band engineering and nanostructure architecture, covering nearly all the material scale, are also presented. Finally, the potential of the application of Cu-based chalcogenides as high-performance thermoelectric materials is briefly discussed from material design to device development.

Promising and Eco‐Friendly Cu2X‐Based Thermoelectric Materials: Progress and Applications

“…Due to high diffusion of Cu, Cu protrusion can easily be observed at the cold side when applying high temperature and high electric current. Figure a shows the Cu protrusion after the stability test . Hence, material stability is important for application of Cu 2 X‐based thermoelectric materials.…”

“…Through nonequilibrium processing, Tan et al have achieved a record‐high zT value of 2.5 in Pb 0.98 Na 0.02 Te‐8%SrTe at 923 K. As a potential substitution for highly toxic PbTe, peak zT values of SnTe of ≈1.5 have also been widely reported . More interestingly, multiple studies demonstrate that the peak zT values of superionic Cu 2 X‐based thermoelectric materials can be higher than 2 in the temperature range from ≈800 to ≈1000 K (mainly Cu 2 Se‐based ones) . Strongly anisotropic and stable BiCuSeO with layered structure has also secured the zT values as high as ≈1 at ≈900 K .…”

Enargite Cu3PS4: A Cu–S‐Based Thermoelectric Material with a Wurtzite‐Derivative Structure

“…For the aforementioned Cu–S‐based materials with ZB‐derivative structures, Cu and S atoms form tetrahedral frameworks, [ 21–25 ] as they do with Zn and S atoms in ZB. Atomic orbitals of Cu‐3d and S‐3p are hybridized at the top of the valence band (VB), which is responsible for p‐type excellent TE power factor S 2 ρ −1 .…”

“…[ 21 ] Furthermore, the complexity of crystal structures of Cu–S‐based materials (e.g., larger primitive cell volume) leads to relatively low κ lat compared with that of ZB (ZnS). [ 24,26 ] For tetrahedrites Cu 12− x Tr x Sb 4 S 13 and colusites Cu 26 Tr 2 M 6 S 32 , unique structural characteristics (i.e., an anharmonic vibration of Cu atom in tetrahedrites, [ 15,16 ] disordered arrangement of cations, and complicated atomic‐scale defects in colusites [ 26,27 ] ) are responsible for further reductions in κ lat to 0.5 W K −1 m −1 . For famatinites Cu 3 SbS 4 without such structural characteristics, κ lat must be suppressed by an enhancement of phonon‐grain boundary scattering and phonon‐point defect scattering.…”

“…Due to the close resemblance of ZB and WZ structures, Cu–S‐based materials with WZ‐derivative structures can be anticipated to have the aforementioned characteristic of the electronic structure responsible for high S 2 ρ −1 for those with ZB‐derivative structures. However, explorations of TE materials have been concentrated on ZB derivatives, [ 21–25 ] with WZ ones receiving scant attention. [ 36,37 ]…”