Hot-Injection Synthesis of Cu-Doped Cu₂ZnSnSe₄ Nanocrystals to Reach Thermoelectric zT of 0.70 at 450°C.
As a new class of potential midrange temperature thermoelectric materials, quaternary chalcogenides like Cu2ZnSnS4 (CZTS) and Cu2ZnSnSe4 (CZTSe) suffer from low electrical conductivity due to insufficient doping. In this work, Cu-doped CZTSe nanocrystals consisting of polygon-like nanoparticles are synthesized with sufficient Cu doping contents. The hot-injection synthetic method, rather than the traditional one-pot method, in combination with the hot-pressing method is employed to produce the CZTSe nanocrystals. In Cu-doped CZTSe nanocrystals, the electrical conductivity is enhanced by substitution of Zn(2+) with Cu(+), which introduces additional holes as charge carriers. Meanwhile, the existence of boundaries between nanoparticles in as-synthesized CZTSe nanocrystals collectively results in intensive phonon-boundary scatterings, which remarkably reduce the lattice thermal conductivity. As a result, an average thermoelectric figure of merit of 0.70 is obtained at 450 °C, which is significantly larger than that of the state-of-the-art quaternary chalcogenides thermoelectric materials. The theoretical calculations from the Boltzmann transport equations and the modified effective medium approximation are in good agreement with the experimental data.
Department of Materials Science, Fudan University , Shanghai 200433, China.|College of Mathematics and Physics, Shanghai University of Electric Power , Shanghai 200090, China.
Dongsheng
D
Chen
Department of Materials Science, Fudan University , Shanghai 200433, China.|Shanghai Advanced Research Institute, Chinese Academy of Sciences , Shanghai 201210, China.
Yan
Y
Zhao
Department of Materials Science, Fudan University , Shanghai 200433, China.
Yani
Y
Chen
Center for Phononics and Thermal Energy Science, School of Physics Science and Engineering, Tongji University , Shanghai 200092, China.
Biao
B
Wang
School of Environmental and Materials Engineering, Shanghai Second Polytechnic University , Shanghai 201209, China.
Yuanyuan
Y
Wang
Center for Phononics and Thermal Energy Science, School of Physics Science and Engineering, Tongji University , Shanghai 200092, China.
Jun
J
Zhou
Department of Materials Science, Fudan University , Shanghai 200433, China.
Ziqi
Z
Liang
Cu2ZnSnSe4; figure of merit; hot-injection; nanocrystals; thermoelectric materials