Bi8Se7: delocalized interlayer π bond interactions enhancing carrier mobility and thermoelectric performance near room temperature,Journal of the American Chemical Society

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Bi8Se7: delocalized interlayer π bond interactions enhancing carrier mobility and thermoelectric performance near room temperature
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2020-06-22 , DOI: 10.1021/jacs.0c05904
Fei Jia _{1,

2} , Yong-Yi Liu ₁ , Yi-Fan Zhang ₁ , Xin Shu ₁ , Ling Chen ₁ , Li-Ming Wu ₂

Affiliation

Environmental heat-to-electric energy conversion provides a promising solution to power sensors used for wearable and portable devices. Yet the near room temperature thermoelectric materials are extremely rare. The natural heterostructure [Bi2]m[Bi2Q3]n family provides an important platform to search and develop the cheaper and less toxic such materials. Yet, the bottle neck problem in this family is how to enhance the interlayer electrical conductivity (σ). Herein, we uncover for the first time that the delocalized π bond interaction between the stacking layers in the [Bi2]m[Bi2Se3]n family effectively increases the interlayer carrier mobility (μH), and σ. Moreover, we propose an empirical index, F = Dpx,py(Bi0)/Dpx,py(Bi3+) along the kz direction in the Brillouin zone, to evaluate the strength of the interlayer delocalized π bond. The F is optimized at the value of 1, under which, the μH is maximized. Interestingly, Bi8Se7 possessing an optimal F = 1.06, is predicted to have the best μH in the [Bi2]m[Bi2Q3]n family. Our subsequent experiments confirm the as-synthesized Bi8Se7 exhibiting an n-type behavior with a μH (33.08 cm2/Vs at 300 K) that is higher than that of BiSe (26.19 cm2/Vs at 300K) and an enhanced σ. Further, the Te/Sb co-doping, via varying the top of the valence band, significantly increases the Seebeck coefficient and eventually enhances the ZT value to ~ 0.7 in Bi5.6Sb2.4Se5Te2 at 425 K along the hot-pressing direction, which is comparable to the optimized value of BiSe. According to the single parabolic band model prediction, the ZT of Bi5.6Sb2.4Se5Te2 may reach ~ 1.2 at 425 K, suggesting a novel and promising n-type thermoelectric material near room temperature.

中文翻译：

Bi8Se7：离域层间 π 键相互作用增强载流子迁移率和室温附近的热电性能

环境热能转换为用于可穿戴和便携式设备的功率传感器提供了一种很有前景的解决方案。然而，接近室温的热电材料极为罕见。天然异质结构 [Bi2]m[Bi2Q3]n 家族为寻找和开发更便宜、毒性更低的此类材料提供了重要平台。然而，这个家族的瓶颈问题是如何提高层间电导率（σ）。在这里，我们首次发现 [Bi2]m[Bi2Se3]n 族中堆叠层之间的离域 π 键相互作用有效地增加了层间载流子迁移率 (μH) 和 σ。此外，我们提出了一个经验指标，F = Dpx,py(Bi0)/Dpx,py(Bi3+) 沿布里渊区的 kz 方向，以评估层间离域 π 键的强度。F 优化为 1，在该值下，μH 最大化。有趣的是，拥有最佳 F = 1.06 的 Bi8Se7 预计在 [Bi2]m[Bi2Q3]n 家族中具有最好的 μH。我们随后的实验证实合成后的 Bi8Se7 表现出 n 型行为，μH（300 K 时为 33.08 cm2/Vs）高于 BiSe（300K 时为 26.19 cm2/Vs）和增强的 σ。此外，Te/Sb 共掺杂通过改变价带顶部，显着增加了塞贝克系数，并最终将 Bi5.6Sb2.4Se5Te2 沿热压方向在 425 K 时的 ZT 值提高到~0.7，这与 BiSe 的优化值相当。根据单抛物线带模型预测，Bi5.6Sb2.4Se5Te2 的 ZT 在 425 K 时可能达到~1.2，

更新日期：2020-06-22

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