Band Engineering SnTe via Trivalent Substitutions for Enhanced Thermoelectric Performance

作者：Xuemei Zhang, Zhongyi Wang, Bo Zou, Madison K. Brod, Jianbo Zhu, Tiantian Jia, Guodong Tang, G. Jeffrey Snyder, Yongsheng Zhang · 发表于：Chemistry of Materials · 年份：2021 · DOI：10.1021/acs.chemmater.1c03198 · 被引用次数：37 · 研究领域：Advanced Thermoelectric Materials and Devices、Chalcogenide Semiconductor Thin Films、2D Materials and Applications

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 (Δ E (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 0.952 Ge 0.016 As 0.016 Te), induces band convergence (Δ E (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.