Substitution Site Selection and Thermoelectric Performance‐Enhancing Mechanism of Cu₁₂Sb₄S₁₃ Doped with Pb/Ge/Sn

Abstract

Tetrahedrite Cu12Sb4S13 has attracted much attention as an earth‐abundant and ecofriendly thermoelectric material with intrinsic low thermal conductivity. Herein, the effects of carbon group elements Pb, Ge, and Sn on the electronic structure and thermoelectric properties of Cu12Sb4S13 are extensively investigated based on first‐principles electronic structure calculations and Boltzmann transport theories. It is found that the most energetically favorable sites for the elements Pb and Ge are the Cu(1) sites, while for Sn atoms they are the Cu(2) sites. And the engineered electronic density of states by Pb/Ge/Sn doping results in a sharp increase of the Seebeck coefficient and a great decrease in carrier thermal conductivity of the host. In addition, the Cu12Sb4S13 compounds substituted with Pb/Ge at Cu(2) sites and Sn at Cu(1) sites have a preferable optimizing thermoelectric performance in a whole. Especially, the optimizing ZT of the host could get an about 15‐time improvement at T = 470 K upon Sn substituting at Cu(1) sites.

Improved Thermoelectric Performance in Ga‐ and Te‐Co‐introduced Tetrahedrite Cu12Sb4S13

“…It was observed that the Ga‐4 s orbitals hybridizes strongly with those of Cu‐3 d and S‐3 p , and the impurity states appear above the E F (see Figure S4, Supporting Information), which is also observed in Cu 11.5 Ge 0.5 Sb 4 S 13 and Cu 11.5 Sn 0.5 Sb 4 S 13 system. [ 33 ] The presence of impurity states can hinder the carrier transport from VB to CB, due to the annihilation between the electrons and holes. In this regard, the electrical conductivity deteriorates.…”

“…[ 27 ] Its estimated carrier concentration is above 3 × 10 21 cm −3 , which is a very high compared to the optimum concentrations (10 19 –10 20 cm −3 ). [ 28 ] In previous studies, many strategies involving the chemical elements doping were proposed to tune the electronic transport [ 23–36 ] and at the same time, reduce the thermal transport properties. For instance, the ZT value of Cu 12− x M x Sb 4 S 13 ( M is Ge or Sn, x = 0.3–0.5) increases from ≈0.46 to ≈0.65 at 665 K. But because the PF decreases, only a slight improvement in ZT value is achieved.…”