通过三价取代的能带工程 SnTe 增强热电性能,Chemistry of Materials

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通过三价取代的能带工程 SnTe 增强热电性能
Chemistry of Materials ( IF 7.2 ) Pub Date : 2021-12-06 , DOI: 10.1021/acs.chemmater.1c03198
Xuemei Zhang _{1,

2} , Zhongyi Wang _{1,

2} , Bo Zou ₃ , Madison K. Brod ₄ , Jianbo Zhu ₅ , Tiantian Jia ₆ , Guodong Tang ₃ , G. Jeffrey Snyder ₄ , Yongsheng Zhang _{1,

2}

Affiliation

SnTe 是作为 p 型热电半导体应用的有吸引力的候选者。原始的 SnTe 化合物由于空穴浓度高、带隙小、轻重带能量差大（ΔE(L – Σ))。为了克服这些问题，我们基于紧束缚 (TB) 模型和密度泛函理论 (DFT) 计算研究了添加三价掺杂剂后的能带结构变化。我们发现调整阳离子和阴离子 s 和 p 轨道的相对现场能量是工程带收敛的潜在途径。除了三价取代之外，与 Ge 共掺杂进一步增强了热电性能。我们发现低浓度的等价 Ge 以及 As 也作为施主 (Sn _0.952 Ge _0.016 As _0.016 Te) 诱导能带收敛 (Δ E(L – Σ) = 0.12 eV) 并扩大带隙 (0.20 eV)。这种带收敛导致峰值功率因数显着增加，而带隙能量的增加抑制了有害的双极效应。我们发现这里的理论和实验结果非常吻合，高功率因数（高加权迁移率）可归因于增加的频带收敛。我们的工作可以有效地筛选与 Ge 共掺杂的基于 SnTe 的材料中的有希望的三价取代物，并找到有希望的候选物以提高热电性能。

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Band Engineering SnTe via Trivalent Substitutions for Enhanced Thermoelectric Performance

SnTe is an attractive candidate for applications as a p-type thermoelectric semiconductor. The pristine SnTe compound exhibits poor thermoelectric performance at high temperatures because of its high hole concentration, small band gap, and large energy difference between the light and heavy bands (ΔE(L – Σ)). To overcome these problems, we investigate band structure changes upon the addition of trivalent dopants based on the tight-binding (TB) model and density functional theory (DFT) calculations. We find that tuning the relative on-site energies of the cation and anion s and p orbitals is a potential route for engineering band convergence. Codoping with Ge in addition to trivalent substitutions further enhances thermoelectric performance. We find that a low concentration of the isovalent Ge as well as As, which also acts as a donor (Sn_0.952Ge_0.016As_0.016Te), induces band convergence (ΔE(L – Σ) = 0.12 eV) and enlarges the band gap (0.20 eV). This band convergence results in a remarkable increase of the peak power factor, while the increased band gap energy suppresses detrimental bipolar effects. We find that the theoretical and experimental results are in good agreement here, and the high power factor (high weighted mobility) can be attributed to the increased band convergence. Our work can efficiently screen the promising trivalent substitutions in SnTe-based materials codoped with Ge and find promising candidates for improved thermoelectric performance.

更新日期：2021-12-28

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