Wu Lihua, Yang Jiong, Chi Miaofang, Wang Shanyu, Wei Ping, Zhang Wenqing, Chen Lidong, Yang Jihui
State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China.
Department of Materials Science and Engineering, University of Washington, Seattle, Washington 98195, United States.
Sci Rep. 2015 Sep 23;5:14319. doi: 10.1038/srep14319.
The low weighted carrier mobility has long been considered to be the key challenge for improvement of thermoelectric (TE) performance in BiTeI. The Rashba-effect-induced two-dimensional density of states in this bulk semiconductor is beneficial for thermopower enhancement, which makes it a prospective compound for TE applications. In this report, we show that intercalation of minor Cu-dopants can substantially alter the equilibria of defect reactions, selectively mediate the donor-acceptor compensation, and tune the defect concentration in the carrier conductive network. Consequently, the potential fluctuations responsible for electron scattering are reduced and the carrier mobility in BiTeI can be enhanced by a factor of two to three between 10 K and 300 K. The carrier concentration can also be optimized by tuning the Te/I composition ratio, leading to higher thermopower in this Rashba system. Cu-intercalation in BiTeI gives rise to higher power factor, slightly lower lattice thermal conductivity, and consequently improved figure of merit. Compared with pristine BiTe0.98I1.02, the TE performance in Cu0.05BiTeI reveals a 150% and 20% enhancement at 300 and 520 K, respectively. These results demonstrate that defect equilibria mediated by selective doping in complex TE and energy materials could be an effective approach to carrier mobility and performance optimization.
长期以来，低加权载流子迁移率一直被认为是提高BiTeI热电（TE）性能的关键挑战。这种体半导体中由Rashba效应诱导的二维态密度有利于提高热电势，这使其成为TE应用的一种有前景的化合物。在本报告中，我们表明，少量Cu掺杂剂的插入可以显著改变缺陷反应的平衡，选择性地介导施主-受主补偿，并调节载流子导电网络中的缺陷浓度。因此，减少了导致电子散射的势波动，并且在10 K至300 K之间，BiTeI中的载流子迁移率可以提高两到三倍。通过调节Te/I组成比，载流子浓度也可以得到优化，从而在这个Rashba系统中产生更高的热电势。BiTeI中的Cu插入导致更高的功率因数、略低的晶格热导率，从而提高了优值。与原始的BiTe0.98I1.02相比，Cu0.05BiTeI的TE性能在300 K和520 K时分别提高了150%和20%。这些结果表明，在复杂的TE和能量材料中通过选择性掺杂介导的缺陷平衡可能是优化载流子迁移率和性能的有效方法。
