Latest progress in the field of thermoelectric materials

Recently, Professor Guodong Tang’s group from the School of Materials Science and Engineering has made significant progress in the field of eco-friendly thermoelectric materials. They synergistically optimize the electrical and thermal transport of MnTe thermoelectric material and successfully achieved high-performance, eco-friendly thermoelectrics through introducing SnTe nanocrystals and band convergence. Research results were published online in international energy top journal “Nano Energy” entitled “High-performance, eco-friendly MnTe thermoelectrics through introducing SnTe nanocrystals and manipulating band structure” (Nano Energy, 2021, 81, 105649; https://doi .org/10.1016/j.nanoen.2020.105649). The first corresponding institution is our university. Professor Guodong Tang and Yongsheng Zhang are the co-corresponding authors of this work. Master student Houquan Deng, is the first author of this work.

Thermoelectric technology is a type of green solid-state ‘heat engine’ that is capable of converting heat to electricity. Thermoelectric materials have attracted extensive attention due to the increasingly energy crisis and environmental issues. Thermoelectric power generation and cooling devices have many outstanding advantages such as no transmission parts, quiet operation, small size, no pollution, no wear, and high reliability. Thermoelectric technology has important application prospects in the fields of thermoelectric power generation and portable refrigeration. The country, industry and enterprises have an urgent demand for thermoelectric conversion technology.

Lead telluride thermoelectric materials are widely used in military and aerospace fields due to their excellent properties. However, they contain lead and are not eco-friendly, which is their fatal disadvantage. Manganese telluride (MnTe) material has the advantages of non-toxic elements, rich sources, and low cost. It is a new type of environmentally friendly medium-temperature thermoelectric material with great development prospects. However, due to the large electronegativity difference between Mn (1.55) and Te (2.10), the strong optical phonon scattering reduces the carrier mobility. Low carrier mobility and low carrier concentration (1018 cm-3) result in relatively low thermoelectric performance, which seriously hinders the wide application of MnTe thermoelectric materials. In response to the above problems, the research team analyzed the multi-valence band energy band transport structure of MnTe and found that the maximum energy difference of the valence band in MnTe is relatively large. It is believed that the energy band can be adjusted to promote the convergence of the MnTe energy band and reduce the energy difference of the MnTe valence band, which can effectively promote the multivalence band transmission of carriers, increase the Seebeck coefficient of the material, and enhance the power factor. It can be supposed to solve the problem of a significant decrease in the Seebeck coefficient and low power factor of the material caused by the low carrier concentration. The innovative idea of optimizing MnTe-based thermoelectric materials is introducing SnTe nanocrystals and band convergence. The study found that the introduction of SnTe with intrinsic Sn vacancies resulted in a significant increase in the carrier concentration of MnTe materials. Simultaneously, SnTe promotes the band convergence of MnTe materials, leading to the significantly increased Seebeck coefficient and a high power factor as 1230 μWm-1K-2. It was found that SnTe nanocrystals significantly enhanced phonon scattering and achieved extremely low lattice thermal conductivity in the material. Through this strategy, the electron and phonon transmission of MnTe is decoupled. The ZT value of the material at 873 K is increased to as high as 1.4, which exceeds the performance of MnTe-based thermoelectric materials that have been reported internationally. This work provides new ideas for the research and development of high-performance, eco-friendly MnTe thermoelectric materials.

Recently, Professor Guodong Tang’s team had devoted to the field of thermoelectric materials and devices and published 64 papers in prestigious journals such as J. Am. Chem. Soc, Nano Energy, J. Mater. Chem. A, Chem. Mater. His team made a series of high-level innovative achievements in the field of high-performance SnSe based thermoelectrics (J. Am. Chem. Soc. 2018, 140, 499; Nano Energy, 2018, 53, 683; J. Am. Chem. Soc. 2016, 138, 13647) and high-efficient and eco-friendly SnTe based thermoelectrics (Nano Energy, 2020, 67, 104261; Nano Energy 2020, 73, 104832) in recent several years. The group was supported by seventeen scientific research projects including the three National Natural Science Foundation of China and five Provincial and Ministerial Level Projects.