Band Engineering for Realizing Large Effective Mass in Cu₃SbSe₄ by Sn/La Codoping

Abstract

How to further improve the thermoelectric performance in Cu3SbSe4-based materials after optimizing its carrier concentration is a difficult issue. The present study attempts to address the issue by investigating thermoelectric performance of Cu3SbSe4 after Sn and La codoping, and all the samples were obtained by using a microwave-assisted hydrothermal synthesis method followed with the spark plasma sintering (SPS) process. First, a series of Cu3Sb1–x Sn x Se4 (x = 0–0.03) compounds have been synthesized, and the hole carrier concentration obviously increased with increasing the Sn content. In addition, La doping subsequently was employed to the Cu3Sb0.98Sn0.02Se4 sample to further increase its power factor by band flattening, resulting in a typical high power factor of 1156.5 μWm–1 K–2 and zT of 0.67 in Cu3Sb0.92Sn0.02La0.06Se4 at 623 K. Our study provides a novel methodology through regulating its carrier concentration and band structure for designing high thermoelectric performance Cu3SbSe4-based materials.

Unconventional Doping Effect Leads to Ultrahigh Average Thermoelectric Power Factor in Cu3SbSe4‐Based Composites

“…Assuming that acoustic phonon scattering is dominant, the single parabolic band model was employed to analyze the electrical transport data by using the Pisarenko plot (Figure 4e), which reveals that the density state of effective mass in Cu 3 SbSe 4 −xCuAlSe 2 composites is around 2.0m e . Such an m d * value is comparable to that for other Cu 3 SbSe 4 -based compounds in literature, [32][33][34][36][37][38]47,48,54] which manifests the fact that the compositing only enlarges the hole concentration while has no evident influence on band structure. The weighted mobility is an important parameter that characterizes the intrinsic electrical property of TE materials.…”

“…It is observed that the weighted mobility increases slightly with increasing CuAlSe 2 content at room temperature and finally converges at high temperature. In this section, it is concluded that the superior electrical performance of Cu 3 SbSe 4 −xCuAlSe 2 composites results from [32][33][34][36][37][38]47,48,54] f) Weighted mobility as a function of temperature.…”

“…c) Carrier concentration and Hall carrier mobility at room temperature of Cu 3 SbSe 4 −xCuAlSe 2 (x = 2, 4, 6, 8, and 10 wt%) composites. d) Comparison of Hall carrier concentration and mobility between this work and doped Cu 3 SbSe 4 in refs [32][33][34][36][37][38]47,48,54]…”

“…a) Electrical conductivity; b) Seebeck coefficient; c) power factor; and d) Hall carrier concentration as functions of temperature. e) Carrier-concentration-dependent Seebeck coefficient with comparison to literature data [32][33][34][36][37][38]47,48,54]. f) Weighted mobility as a function of temperature.…”

Realizing High Thermoelectric Performance in the ZnTe-Alloyed CuGaTe2 through Band Engineering

“…(The calculation formula is in the Supporting Information.) It can be seen from the figure that the effective mass 33,34 of the doped samples is significantly higher than that of the undoped CuGaTe 2 , which is due to the degeneracy of the band 35 and the increase in the electron density of states near the Fermi level 30 after the introduction of Zn. At the same time, the band between the point Z− and the point X− in the Brillouin zone becomes slightly flat, which is consistent with the theoretical value of the calculated band, making the effective mass of the (CuGaTe 2 ) 1−x (2ZnTe) x samples higher than that of the pure phase CuGaTe 2 under the same carrier concentration.…”