Hot-Injection Synthesis of Cu-Doped Cu₂ZnSnSe₄ Nanocrystals to Reach Thermoelectric zT of 0.70 at 450°C

Dongsheng Chen; Yan Zhao; Yani Chen; Biao Wang; Yuanyuan Wang; Jun Zhou; Ziqi Liang

doi:10.1021/acsami.5b08011

Hot-Injection Synthesis of Cu-Doped Cu₂ZnSnSe₄ Nanocrystals to Reach Thermoelectric zT of 0.70 at 450°C

ACS Appl Mater Interfaces. 2015 Nov 11;7(44):24403-8. doi: 10.1021/acsami.5b08011. Epub 2015 Oct 28.

Authors

Dongsheng Chen^{1

2}, Yan Zhao^{1

3}, Yani Chen¹, Biao Wang⁴, Yuanyuan Wang⁵, Jun Zhou⁴, Ziqi Liang¹

Affiliations

¹ Department of Materials Science, Fudan University , Shanghai 200433, China.
² College of Mathematics and Physics, Shanghai University of Electric Power , Shanghai 200090, China.
³ Shanghai Advanced Research Institute, Chinese Academy of Sciences , Shanghai 201210, China.
⁴ Center for Phononics and Thermal Energy Science, School of Physics Science and Engineering, Tongji University , Shanghai 200092, China.
⁵ School of Environmental and Materials Engineering, Shanghai Second Polytechnic University , Shanghai 201209, China.

PMID: 26497358
DOI: 10.1021/acsami.5b08011

Abstract

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.

Keywords: Cu2ZnSnSe4; figure of merit; hot-injection; nanocrystals; thermoelectric materials.

Publication types

Research Support, Non-U.S. Gov't