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首页> 外文期刊>Advanced Functional Materials >Positive Effect of Ge Vacancies on Facilitating Band Convergence and Suppressing Bipolar Transport in GeTe-Based Alloys for High Thermoelectric Performance
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Positive Effect of Ge Vacancies on Facilitating Band Convergence and Suppressing Bipolar Transport in GeTe-Based Alloys for High Thermoelectric Performance

机译：Ge空位对促进高热电性能的GeTe基合金中能带收敛和抑制双极传输的积极影响

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摘要

Because the intrinsic Ge vacancies in GeTe usually lead to high hole concentration beyond the optimal range, many previous studies tend to consider Ge vacancies as negative effects on increasing the figure of merit ZT of GeTe-based alloys, and consequently have proposed various approaches to suppress Ge vacancies. However, in this work, it is demonstrated that the Ge vacancies can have great positive effects on enhancing the ZT of GeTe-based alloys when the hole concentration falls into the optimal range. First, hole concentration of GeTe is reduced close to the optimal range by co-alloying of Pb and Bi, and then the Ge vacancies are increased by adding excess Te into the Ge0.8Pb0.1Bi0.1Te1+x. The Ge vacancies can cause lattice shrinkage and promote rhombohedral-to-cubic phase transition. As revealed by first-principle calculations, theoretical simulations, and experimental tests, Ge vacancies can facilitate the band convergence, suppress the bipolar transport at higher temperature range, and reduce the lattice thermal conductivity. Combining these effects, a peak ZT of 1.92 at 637 K and an average ZT of 1.34 within 300-773 K in Ge0.8Pb0.1Bi0.1Te1.06 can be obtained, demonstrating the great significance of utilizing vacancy-type defects for enhancing ZT.
机译：由于GeTe的固有Ge空位通常会导致空穴浓度超出最佳范围，因此许多先前的研究倾向于将Ge空位视为对提高GeTe基合金的ZT值的不利影响，因此提出了多种抑制方法。葛空缺。然而，在这项工作中，证明了当空穴浓度落在最佳范围内时，Ge空位对增强GeTe基合金的ZT具有很大的积极作用。首先，通过Pb和Bi的共同合金化，将GeTe的空穴浓度降低至接近最佳范围，然后通过向Ge0.8Pb0.1Bi0.1Te1 + x中添加过量的Te来增加Ge空位。 Ge空位可引起晶格收缩并促进菱形向立方相变。正如第一性原理计算，理论模拟和实验测试所揭示的那样，Ge空位可以促进能带收敛，在较高温度范围内抑制双极传输，并降低晶格热导率。结合这些效应，可以在Ge0.8Pb0.1Bi0.1Te1.06中获得637 K时的ZT峰值1.92和300-773 K中的平均ZT值1.34，这表明利用空位型缺陷来增强ZT具有重要意义。 。

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