Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University , Singapore 637371, Singapore.
College of Materials Science and Engineering, Shenzhen University , Shenzhen 518060, P. R. China.
ACS Appl Mater Interfaces. 2017 Apr 12;9(14):12501-12510. doi: 10.1021/acsami.7b01473. Epub 2017 Mar 30.
Minority carrier blocking through heterointerface barriers has been theoretically proposed to enhance the thermoelectric figure of merit (ZT) of bismuth telluride based nanocomposites at elevated temperatures recently (Phys. Rev. B 2016, 93, 165209). Here, to experimentally realize the minority carrier blocking, a liquid-phase sintering process enabled by excess Te is applied to the solution-processed BiSbTe nanocomposites to introduce interfacial energy barriers. The controlling parameters in the liquid-phase sintering process such as the amount of excess Te, sintering temperature and holding time, and the Bi composition (x) are systemically tuned and investigated to fully understand the minority carrier blocking mechanism. These interface-engineering parameters are optimized for introducing maximum lattice imperfections and band-bending interfaces that are responsible for blocking the minority carrier and wide-range scattering of the phonons toward enhanced thermoelectric performance. High ZT > 1.4 at 375 K is realized in the BiSbTe sample, which is much higher than those of the state-of-the-art commercial ingots (ZT ∼ 1) and other solution-processed nanocomposites. The enhanced ZT at elevated temperatures is mostly due to the suppression of bipolar thermal conductivity by minority carrier blocking as well as the reduction of lattice thermal conductivity. Adapting this solution synthesis process to design favorable heterointerfaces for minority carrier blocking in the liquid-phase sintering process holds promise to further enhance the ZT values.
最近有理论提出，通过异质界面势垒来阻止少数载流子，可以提高碲化铋基纳米复合材料在高温下的热电优值（ZT）（Phys. Rev. B 2016, 93, 165209）。在这里，为了实验实现少数载流子阻挡，通过过量 Te 实现的液相烧结工艺被应用于溶液处理的 BiSbTe 纳米复合材料中，以引入界面能垒。液相烧结工艺中的控制参数，如过量 Te 的量、烧结温度和保温时间以及 Bi 组成（x），被系统地调整和研究，以充分理解少数载流子阻挡机制。这些界面工程参数被优化，以引入最大晶格缺陷和能带弯曲界面，从而阻止少数载流子并对声子进行大范围散射，以提高热电性能。在 375 K 时，BiSbTe 样品的 ZT 值>1.4，远高于最先进的商业锭（ZT∼1）和其他溶液处理的纳米复合材料。在高温下增强的 ZT 主要归因于少数载流子阻挡抑制双极热导率以及晶格热导率的降低。通过将这种溶液合成工艺应用于液相烧结工艺中设计有利于少数载流子阻挡的有利异质界面，有望进一步提高 ZT 值。
