Liang Gege, Lyu Tu, Hu Lipeng, Qu Wanbo, Zhi Shizhen, Li Jibiao, Zhang Yang, He Jian, Li Junqin, Liu Fusheng, Zhang Chaohua, Ao Weiqin, Xie Heping, Wu Haijun
College of Materials Science and Engineering, Shenzhen Key Laboratory of Special Functional Materials, Guangdong Research Center for Interfacial Engineering of Functional Materials, Guangdong Provincial Key Laboratory of Deep Earth Sciences and Geothermal Energy Exploitation and Utilization, Institute of Deep Earth Sciences and Green Energy, Shenzhen University, Shenzhen 518060, China.
College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China.
ACS Appl Mater Interfaces. 2021 Oct 6;13(39):47081-47089. doi: 10.1021/acsami.1c14801. Epub 2021 Sep 27.
In thermoelectrics, the material's performance stems from a delicate tradeoff between atomic order and disorder. Generally, dopants and thus atomic disorder are indispensable for optimizing the carrier concentration and scatter short-wavelength heat-carrying phonons. However, the strong disorder has been perceived as detrimental to the semiconductor's electrical conductivity owing to the deteriorated carrier mobility. Here, we report the sustainable role of strong atomic disorder in suppressing the detrimental phase transition and enhancing the thermoelectric performance in GeTe. We found that AgSnSe and Sb co-alloying eliminates the unfavorable phase transition due to the high configurational entropy and achieve the cubic GeSbTe(AgSnSe) solid solutions with cationic and anionic site disorder. Though AgSnSe substitution drives the carrier mean free path toward the Ioffe-Regel limit and minimizes the carrier mobility, the increased carrier concentration could render a decent electrical conductivity, affording enough phase room for further performance optimization. Given the lowermost carrier mean free path, further Sb alloying on Ge sites was implemented to progressively optimize the carrier concentration and enhance the density-of-state effective mass, thereby substantially enhancing the Seebeck coefficient. In addition, the high density of nanoscale strain clusters induced by strong atomic disorders significantly restrains the lattice thermal conductivity. As a result, a state-of-the-art ≈ 1.54 at 773 K was attained in cubic GeSbTe(AgSnSe). These results demonstrate that the strong atomic disorder at the high entropy scale is a previously underheeded but promising approach in thermoelectric material research, especially for the numerous low carrier mobility materials.
在热电学中，材料的性能源于原子有序性和无序性之间的微妙平衡。一般来说，掺杂剂以及由此产生的原子无序对于优化载流子浓度和散射短波长热载声子是不可或缺的。然而，由于载流子迁移率下降，强无序被认为对半导体的电导率不利。在此，我们报道了强原子无序在抑制有害相变和提高GeTe热电性能方面的可持续作用。我们发现，AgSnSe和Sb共合金化由于高组态熵消除了不利的相变，并实现了具有阳离子和阴离子位点无序的立方GeSbTe(AgSnSe)固溶体。尽管AgSnSe替代使载流子平均自由程趋向于Ioffe-Regel极限并使载流子迁移率最小化，但增加的载流子浓度可带来可观的电导率，为进一步的性能优化提供足够的相空间。鉴于最低的载流子平均自由程，在Ge位点上进一步进行Sb合金化以逐步优化载流子浓度并提高态密度有效质量，从而大幅提高塞贝克系数。此外，由强原子无序诱导的高密度纳米级应变团簇显著抑制了晶格热导率。结果，立方GeSbTe(AgSnSe)在773 K时达到了约1.54的先进ZT值。这些结果表明，高熵尺度下的强原子无序是热电材料研究中一种此前未被充分重视但很有前景的方法，特别是对于众多低载流子迁移率材料而言。
