Minority Carrier Blocking to Enhance the Thermoelectric Performance of Solution-Processed BixSb2-xTe3Nanocomposites via a Liquid-Phase Sintering Process.
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 BixSb2-xTe3nanocomposites 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 Bi0.5Sb1.5Te3sample, 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.
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.
Chaohua
C
Zhang
Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University , Singapore 637371, Singapore.
Hongkuan
H
Ng
School of Mechanical and Aerospace Engineering, Nanyang Technological University , Singapore 639798, Singapore.
Zhong
Z
Li
School of Mechanical and Aerospace Engineering, Nanyang Technological University , Singapore 639798, Singapore.
Khiam Aik
KA
Khor
Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University , Singapore 637371, Singapore.
Qihua
http://orcid.org/0000-0002-2555-4363
Q
Xiong
bismuth antimony telluride; liquid-phase sintering; minority carrier blocking; solution-processed; thermoelectrics