The thermoelectric effect converts a temperature gradient to electricity directly. The energy conversion efficiency of these materials are defined by the dimensionless figure of merit (ZT). The high thermal conductance of graphene and its related nanostructure derivatives means that they are not efficient thermoelectric materials and have a ZT of around 0.05. In order to overcome this, researchers have turned their attention to beta-graphyne (Β-graphyne), an allotrope of graphene. It has been suggested that the phonon contributed thermal conductance of graphyne is fundamentally lower than that of graphene which makes it an attractive thermoelectric material.

Unique thermal transport properties

Using a non-equilibrium Green’s function method, the researchers find that the thermal conductance of Β-graphyne nanoribbons (BGYNRs) is only 26% of that of their graphene counterparts. It also shows evident directional dependence. No matter what the kind of edge terminal is, the thermal conductance of armchair edged BGYNRs (A-BGYNRs) present abnormal stepwise width dependence.

Thermoelectric performance

Combined with the electronic transport calculation, the thermoelectric performance of BGYNRs is also investigated. The numerical simulation results reveal that, compared with the graphene counterparts (ZT ~0.05), Β-graphyne possesses a superior thermoelectric performance with a figure of merit (ZT) achieving 0.5 at room temperature.

Nanostructure improvements

Based on the samples of BGYNRs with a zigzag edge, the influence of edge and central geometric modulations on the thermoelectric efficiency are considered. Researchers find that the thermoelectric performance can be further enhanced dramatically (ZT can even exceed 1.5 at room temperature) and this strongly depends on the structure parameters.

More information about the research can be found in the journal Nanotechnology 25 245401.

Further reading

Hybrid nanomaterial enhances performance of thermoelectric generator (Oct 2012)
Doped CNTs make better thermoelectrics (May 2014)
Could graphynes be better than graphene? (Mar 2012)
Thermoelectric nanodevices: Catering for global energy needs little by little (April 2014)