Approaching the maximum thermoelectric figure of merit of 2D materials by nanoengineering

Nanoengineering techniques have been developed to reduce thermal conductivity (κ) and improve the thermoelectric figure of merit (ZT) of materials. However, both these strategies have had their own limitations.

Firstly, due to the nanopatterns only reducing the κ in a single direction, is difficult to reduce the total κ of thermal isotropic materials.

Secondly, when nanoengineering the material to increase ZT by lowering its κ, the nanopatterned sample with large porosity (> 0.5) can greatly remove its volume and suppress the electron mean free path, which would also significantly reduce the electrical conductivity (σ) and resulted in a low increase of the ZT value.

CARMEN will overcome these limitations by taking two advantages of emerging two-dimensional (2D) materials, especially SnSe2: a high Seebeck coefficient of 500 μV/K at 298 K and a high anisotropic κ ratio of ~ 8.4.

Therefore, nanoengineering 2D materials can reduce their κ to approach the maximum value of ZT with a limited reduction in σ.

Additionally, the phonon drag of SnSe2 was first revealed by the applicant during a three-month research visit in the supervisor's group, which will be further investigated by CARMEN.

To understand and exploit the thermoelectric properties of 2D materials, CARMEN will design, construct, measure, and explore nanopatterned SnSe2 to approach its maximum thermoelectric ZT value above room temperature and to manipulate the phonon drag in SnSe2 at low temperatures (1 - 273 K).

The project is motivated in part by the urgent need for highly thermoelectric ZT materials to harvest waste heat from electronics, and in part by the fundamental quest toward understanding and manipulating the phonon-electron interaction in 2D materials.

It represents an extraordinary training opportunity on complementary scientific and soft skills for the applicant and has transformational impact potential on flexible thermoelectric devices, thermal engineering, quantum technologies, and beyond.