A Universal Approach for Room-Temperature Printing and Coating of Two-Dimensional Materials

We here introduce a new approach for the formulation of 2D materials into printable or coatable inks for the fabrication of functional devices [1]. In a traditional ink formulation additives are introduced in large concentrations to address processing challenges, but they drastically degrade the electronic properties of the materials. For additive removal, a high-temperature post-deposition treatment can be used, but this complicates the fabrication process and limits the choice of materials (i.e., no heat-sensitive materials). The unique properties of 2D materials offer the possibility to formulate additive-free inks in which the roles of the additives are taken over by van der Waals (vdW) interactions. The approach is universal and is demonstrated with a number of 2D materials. In this new class of inks, solvents are dispersed within the interconnected network of 2D materials, increasing the possible choice of solvents over traditional inks where dispersibility-related issues limit the selection. Furthermore, flow behavior of the inks and mechanical properties of the resultant films are mainly controlled by the inter-flake vdW attractions and can be largely controlled via concentration and choice of solvent. The structure of the vdW inks, their rheological properties, and film-formation behavior are discussed in detail. A method for large-scale production of inks for all major high-throughput printing and coating techniques is introduced. In a first application we demonstrate a Thin Film Transistor fully printed from 2D materials, with no additional heat treatment and competitive performance.<br/>[1] S. Abdolhosseinzadeh, C. Zhang, R. Schneider, M. Shakoorioskooie, F. Nüesch, J. Heier, Advanced Materials, Oct. 2021, https://onlinelibrary.wiley.com/doi/10.1002/adma.202103660