Anisotropic thermal conductivity of printed films made of 2D-materials based inks

Graphene and other 2-dimensional (2D) materials are the subject of intense research due to their distinct properties, particularly for electronic and optoelectronic applications. Solution-processed 2D materials can accelerate the progress even further due to their compatibility with flexible substrates, large scale and low-cost device fabrication. In addition, printed films of such inks, could have potential use in thermal and thermoelectric applications. However, very little is known about the thermal properties of 2D-materials based inks due to the challenge and complexity associated with measuring their thermal properties, which are highly anisotropic. To develop applications based on the thermal properties of 2D-materials based inks, it is of fundamental importance to understand the relation between structure and property, and to determine how electron and heat transport relate in 2D materials.
Here, we present the electrical conductivity and in-plane and out-of-plane thermal conductivity of graphene and other 2D-materials thin films, produced by ink-jet printing of water-based 2D-materials inks. Thermal anisotropies of 40:1 are observed together with ultra-low cross-plane thermal conductivity well below 1 W/mK.