Thermoelectric properties of chalcopyrite type CuGaTe2 and chalcostibite CuSbS2

Abstract

Electronic and transport properties of CuGaTe 2 , a hole-doped ternary copper based chalcopyrite type semiconductor, are studied using calculations within the Density Functional Theory and is associated with anisotropic transport from a combination of heavy and light bands. Also for CuSbS 2 (chalcostibite) a better performance is obtained for p-type than for n-type doping. The variation of the thermopower as a function of temperature and concentration suggests that CuSbS 2 will be a good thermoelectric material at low temperatures, similarly to the isostructural CuBiS 2 compound.

Role of interlayer coupling for the power factor ofCuSbS2andCuSbSe2

“…Our results for bulk CuSbS 2 are quantitatively similar to those of the calculations reported in Ref. [4], and the value of S = 300 μV/K obtained for bulk CuSbSe 2 at 300 K and a hole doping of 5.2 × 10 19 cm −3 agrees well with experiment (S = 375 μV/K) [3]. We further observe that σ increases in both compounds with the doping (see Fig.…”

“…The band gap is found to be indirect, in agreement with the theoretical results in Refs. [4,36] and the experimental results in Refs. [37,38].…”

“…The transport properties are calculated by solving the Boltzmann transport equation within the rigid band (which assumes that the band structure of the host is not altered by doping, and only the chemical potential changes) and constant relaxation time (which assumes that the relaxation time has no energy dependence, which is valid for temperatures up to about 700 K [4]) approximations, as implemented in the BoltzTraP code [30]. Dense 52 × 85 × 22 (bulk) and 98 × 62 × 1 (monolayer) k meshes are used to obtain accurate carrier group velocities, which determine the transport properties.…”

“…The thermoelectric properties have been studied only recently, demonstrating high values of the Seebeck coefficient (S) and power factor (S 2 σ ), where σ is the electrical conductivity [3,4]. Thermoelectric devices can be used for energy harvesting by converting waste heat into electricity and can find applications in electronic refrigeration, for example [5].…”

“…A high value of ZT therefore requires high S 2 σ and low κ. Since both S and σ are given by the band structure and vary oppositely under doping [6], good thermoelectric properties are often found in narrow band gap semiconductors with a rather small amount of available charge carriers, such as CuBiS 2 [7], CuGaTe 2 [4], PbTe [8], and Bi 2 Te 3 [9].…”