Research in the School of Engineering and Materials Science has shown a 25-fold improvement in the thermoelectric figure of merit (ZT) in aligned polymer films.

Thermoelectric materials have the ability to convert heat in the form of temperature gradients into electricity. Research in Dr Fenwick's group has been focussing on organic and hybrid materials for thermoelectric energy conversion as these materials offer enhanced processability and a more sustainable solution. However, the performance of these thermoelectric materials does not currently match state-of-the-art ceramic materials.

One reason is the semicrystalline morphology. Control of nanoscale morphology in polymer thermoelectric materials is critical to their performance. In collaboration with Drs Brinkmann and Biniek at the CNRS in Strasbourg, Dr Fenwick's group have studied highly aligned polymer thermoelectric materials prepared by mechanical rubbing. The work reveals a remarkable range of thermal conductivities in these materials from <0.2 W m−1 K−1 to >1 W m−1 K−1. However, despite the discovery of high thermal conductivity states, mechanical rubbing results in a power factor enhancement along the rubbing direction that far outweighs the increase in thermal conductivity, resulting in a 25-fold improvement in the thermoelectric figure of merit, ZT, as compared to the isotropic doped films.

This work highlights the importance of morphology when developing polymer thermoelectric generators, and gives a possible route to enhanced power generation.

Updated by: Oliver Fenwick