Intersheet Electrical Resistance Reduction in Graphene Nanosheet Networks via Visible Photon-Assisted Thermal Treatment: Implications of Conductive Coating Applications

Graphene demonstrates enormous potential for lightweight electronic and conducting applications due to its exceptional physical properties. Liquid exfoliation of graphite to graphene is scalable and economical, which provides a significant advantage to the development of layered material manufacturing. However, minimizing the energy budget to transform colloidal dispersions into a thin-film form with enhanced electrical conduction is the key for reducing the cost of production of graphene thin films. This study explores annealing of the thin films using photon sources including ultraviolet, focused solar, infrared radiation, and matter-based techniques to control the morphology and electrical resistance of the self-assembled graphene (SAG) nanosheet networks. The SAG films are characterized by Raman spectroscopy, electron microscopy, and current–voltage characteristics before and after the annealing. We found that, after 10 min of treatment, the Raman defect ratio (ID/IG) of focused solar radiation (FSR) annealed SAG films decreased by 65% compared to conventional resistive annealing. The electrical resistance of SAG films is reduced from 40 to 5 kΩ after the treatment. The balance between heating from photons and radiation pressure effectively reduces the intersheet resistance and improves the electrical conduction of graphene networks. The experiments confirm that photon-assisted irradiation improves the electrical property of self-assembled thin films of graphene nanosheets by aligning the nanosheets in-plane with minimal energy input. The photon-assisted thermal treatment is a practical and scalable way to improve the performance of graphene-based thin films for lightweight and electrically conducting channel applications such as flexible electronics and thin-film EMI shielding.