Manipulation of the crystal structure defects: An alternative route to the reduction in lattice thermal conductivity and improvement in thermoelectric performance of CuGaTe2

Abstract

Here, we present the manipulation of the crystal structure defects: an alternative route to reduce the lattice thermal conductivity (κL) on an atomic scale and improve the thermoelectric performance of CuGaTe2. This semiconductor with defects, represented by anion position displacement (u) and tetragonal deformation (η), generally gives low κL values when u and η distinctly deviate from 0.25 and 1 in the ideal zinc-blende structure, respectively. However, this semiconductor will show high Seebeck coefficients and low electrical conductivities when u and η are close to 0.25 and 1, respectively, due to the electrical inactivity caused by an attractive interaction between donor-acceptor defect pairs (GaCu2+ + 2VCu−).

Site occupations of Zn in AgInSe2-based chalcopyrites responsible for modified structures and significantly improved thermoelectric performance

“…4c). 23 However, the case is different in IApoor in terms of the above analysis. Because the anion displacement u upon substitution of Zn for In changes in an opposite way as it does upon Zn substitution for Ag, therefore, the deviation of the u value from 0.25 might become smaller with Zn content increasing in IA-poor.…”

Enhanced thermoelectric performance of a chalcopyrite compound CuIn3Se5−xTex (x = 0~0.5) through crystal structure engineering

“…The highest ZT value of the sample at x  = 0.1 is 0.4 at 930 K. An insert is the plot of ZT against x value in CuIn 3 Se 5− x Te x . Although this ZT value is still lower than those of other chalcopyrites, such as CuGaTe 2 -based (ZT = 1.22 at 850 K13; 0.91~1.07 at 703 K171938; 1.4 at 940 K39), AgInSe 2 -based alloys (1.05@815 K18, and CuInTe 2 -based (0.69@737 K40, 1.18 and 1.3 at 850 K4142), it is ~2.6 times that of intrinsic CuIn 3 Se 5 (ZT = ~0.15).…”

“…ZT value vs ∆ u is plotted in Fig. 6, where the ZTs against ∆ u in other chalcopyrite compounds, such as, CuGa 1− x In x Te 2 38, annealed CuGaTe 2 19 and CuIn 1− x Zn x Te 2 40, are also presented for comparison. It is worth noting that at ∆ u  = 0, corresponding to x  = 0.15, neither the E g ( E g  ≈ 0.90 eV) nor the ZT value reaches the highest, see Figs 5a and 6.…”

“…The maximum ZTs from different chalcopyrites, such as, CuGa 1− x In x Te 2 38, annealed CuGaTe 2 19 and Cu 1− x In 1− x Zn 2 x Te 2 40 are presented for comparison. These chalcopyrite compounds all show that they do not have the highest ZTs at ∆ u  = 0, but at a certain ∆ u value.…”

“…In this case, the least lattice distortion can be obtained and phonon scattering in point defect gets the minimum. As a result, the highest lattice part κ L can be attained19.…”