Synergistic modulation of electrical and thermal transport toward promising n-type MgOCuSbSe2 thermoelectric performance by MO-intercalated CuSbSe2

Abstract

The layered ternary CuSbSe₂ semiconductor with ultralow thermal conductivity is particularly suitable for thermoelectric applications. Nevertheless, its poor electrical conductivity greatly lowers the dimensionless figure of merit ZT and accordingly limits its thermoelectric applications. Here, we use first-principles calculations combined with semi-classical Boltzmann transport theory to evaluate the thermoelectric properties of MO-intercalated (M = Mg, Ca, Sr, and Ba) CuSbSe₂. Compared with CuSbSe₂, MO-intercalated CuSbSe₂ semiconductors, as a new class of semiconductors, host distorted lattices with low symmetry monoclinic structures. Such a structure feature provides desired channels for electron transport between adjacent layers and accordingly enhances electrical transport properties. Meanwhile, the MO intercalation effectively softens phonons and gives rise to an ultralow lattice thermal conductivity in MOCuSbSe₂. These synergistically yield a high figure of merit ZT of ∼4.17 for MgO-intercalated CuSbSe₂ at 200 K with electron doping being n = 10¹⁸ cm⁻³. Our study provides an effective route to improve the thermoelectric performance of layered CuSbSe₂ by designing new multicomponent thermoelectric compounds with alternatively stacked [CuSbSe₂] (electronic conduction units) and [MO] (electronic insulation units) layers. The approach can be extended to similar chalcostibite compounds for screening and designing thermoelectric materials.