Nanowires display enhanced thermoelectric potential

Nanowires as thin as one to two atoms can convert heat to electricity more efficiently than bulk materials, offering the potential for their use in sustainable energy, according to UK research.

Thermoelectric materials convert waste heat to electrical energy through a process known as the Seebeck effect.

The materials are used in applications such as power plants and cars, for example, where they convert waste exhaust heat into sustainable energy.

Now researchers at the University of Warwick, in collaboration with the Universities of Cambridge and Birmingham, have discovered that shaping thermoelectric materials into the thinnest possible nanowires means they conduct less heat and more electricity at the same time. This results in significantly greater efficiency than bulk versions of the materials.

The researchers were investigating the crystallisation of tin telluride in extremely narrow carbon nanotubes, which they used as templates for the formation of the materials in their one-dimensional form, according to the paper’s first author Dr Andrij Vasylenko, from the University of Warwick’s Department of Physics.

“By sublimation, we converted the material into its gaseous form, and the gas then filled the tube and crystallised,” said Vasylenko.

At the same time, they carried out theoretical research, using quantum mechanical computations, to understand the formation of the tin telluride nanowires, and how their structure is affected by different external conditions such as pressure, temperature and the diameter of the carbon nanotubes.

The researchers, including Dr Andrew J Morris’s group at the University of Birmingham, were able to establish a direct link between the size of the nanotube template and the resulting structure of the formed nanowire.

In a paper published in ACS Nano, they also demonstrated that the technique can be used to regulate the thermoelectric efficiency of tin telluride formed into nanowires just one to two atoms in diameter.

The researchers now hope to carry out further research, including studying the combined thermoelectric potential of the tin telluride nanowires and the carbon nanotubes, with the aim of developing them into useable thin films, according to Dr Jeremy Sloan at the University of Warwick.

To this end, Sloan has been awarded a five-year EPSRC Established Career Fellowship to investigate the atomically thin nanowires.

“We have so far managed to illustrate the potential of these materials, and that potential is something that I very much hope to exploit,” he said.