Enhanced thermoelectric performance in Sb–Br codoped Bi₂Se₃ with complex electronic structure and chemical bond softening

Abstract

A detailed description of the charge density difference of BiSb(Se0.92Br0.08)3.

Improved Thermoelectric Performance of NbCoSb with Intrinsic Nb Vacancies and Ni-Doping-Induced Band Degeneracy

“…There are three other conduction band extrema (CBEs) with almost identical energies: one appears at the M points with N v = 2, one emerges at the Z points with N v = 2, and the other is located at M, X points with N v = 2. Because these valence valleys have very close energies (shown in Table ), while the energy difference between the CBM and the third valence valley is smaller than ∼0.097 eV, there is a valley degeneracy of 10 around the CBM that can be easily crossed at elevated temperatures, allowing the electrical transport properties to be promoted . Hence, the 20% intrinsic Nb vacancies increase the N v from 4 at the X point of CBM of NbCoSb to 10 of Nb 0.8 CoSb.…”

“…10 1), while the energy difference between the CBM and the third valence valley is smaller than ∼0.097 eV, there is a valley degeneracy of 10 around the CBM that can be easily crossed at elevated temperatures, allowing the electrical transport properties to be promoted. 3 Fortunately, Nb 0.8 CoSb with N v = 10 may have sufficient μ to enable good TE properties. 7 For degenerate semiconductors or metals, S can be approximated to the Mott formula: 33…”

“…The efficiency of TE materials is determined by the dimensionless figure of merit italicz italicT = S 2 σ T / κ where S , σ, κ, and T represent the Seebeck coefficient, electrical conductivity, total thermal conductivity (including the lattice contribution κ L and carrier contribution κ e ), and absolute temperature, respectively . To date, decoupling of these electronic parameters and minimizing κ L (the only independent parameter) have proved to be effective strategies for improving zT . The former can be realized by band engineering approaches through increasing the number of effective energy valleys.…”

“…2 To date, decoupling of these electronic parameters and minimizing κ L (the only independent parameter) have proved to be effective strategies for improving zT. 3 The former can be realized by band engineering approaches through increasing the number of effective energy valleys. The latter can be achieved by defect engineering to strengthen the phonon scattering.…”

Realizing Remarkable Improvement of Electrical Performance in N‐Type BiSbSe3 via In Situ Compositing

“…Contributed to the high-μ Bi 2 SbSe 3 and percolation effect of in situ BiSbSe 3 -Bi 2 SbSe 3 composite, the extremely high carrier mobility of 11.4 cm 2 V −1 s −1 is obtained under a high carrier concentration of 2.07 × 10 20 cm −3 (Figure 5D). The outstanding μ of in situ composites in this work exhibits an advantage over the published n-type BiSbSe 3 materials, such as Cl-doped, [22,29] I-doped, [12a,30] Br-doped, [14,31] Zr & Br-codoped, [12b] and Br-doped with percolation effect BiSbSe 3 samples. [21] As a result, the ZT value of BiSbSe 3 -13 vol% Bi 2 SbSe 3 in situ composite sample performs highly competitively against previously n-type BiSbSe 3 reports over the whole working temperature (Figure 5E), which leads to a high average ZT (ZT ave ) of ≈0.65 between 300-750 K. As shown in Figure 5F, such report-breaking ZT ave is outstanding compared with all of the published n-type BiSbSe 3 samples, such as ≈0.57 in Br-doped BiSbSe 3 sample, [14] ≈0.55 [12a] and ≈0.38 [30] in I-doped BiSbSe 3 sample, ≈0.51 in Cl-doped BiSbSe 3 sample, [22] and ≈0.44 in Zr & Br-codoped BiSbSe 3 sample.…”