Thermo-optical characterization and thermal properties of graphene-polymer composites: a review

Graphene-polymer composites have shown great promise as thermal interface materials to replace state-of-the-art silver-grease thermal pastes. A deeper understanding of their inherent thermal properties irrespective of their interfacial thermal resistivity with other systems is required to develop them with a sufficient degree of generality for a host of thermal applications. This also requires that thermal transport measurements need to be carried out contactlessly. Thermo-optical characterization methods based on the photothermal effect are valuable contactless techniques for determining the thermal properties of thin-film materials without the need to transfer heat from other media to the sample under investigation. However, they require a careful and often complex modeling procedure to extract thermal properties of the film-substrate-environment system, and the results they provide are often depending on the specific model used to interpret the measured data. In this article, we offer a review of photothermal and thermo-optical methods, with a focus on the recent progress in using them for developing the thermal properties of graphene-polymer composites. We discuss some of the methods used for aligning graphene platelets with each other, to improve their directional thermal conductivity, and to understand how thermo-optical pump-probe techniques can be used for characterizing such systems, with PEDOT: PSS-graphene composite systems as working examples.