A Study on Reduced Graphene Oxide in Large-area Transparent Heaters for Defrosting

Transparent heaters are promising devices because of their versatile applications in vehicles, smart windows, and sensors, etc. Indium tin oxide is widely used for transparent heater materials due to its high electronic conductivity and visible light transmittance. However, the cost of indium is too high, and its fabrication needs sophisticated processes, so that many studies have focused on alternative materials which are inexpensive and easy-to-synthesize. Graphene is a two-dimensional material in which carbon atoms bond to form a hexagonal structure, and it can be an alternative material due to its superior electronic/ thermal conductivity and cost-effectiveness. Here, we chemically treated graphite to synthesize large-sized graphene oxide (LGO), and coated it on a glass substrate, followed by reduction using hydrogen iodide for large-sized reduced graphene oxide (LrGO) on glass. From surface characterizations, we confirmed that the lateral size of the LGO was over 50 mu m and the LGO sheets were uniformly coated on the glass, which minimized intersheet contact resistance. Structural characterizations demonstrated that the LGO sheets were reduced to LrGO and the LrGO sheets coated on the glass showed a transmittance of 76.2 % at 550 nm with a sheet resistance of 0.98 k Omega. Finally, the temperature of the substrate increased up to 30 degrees C when 30 V of voltage was applied for 5 min, and the frost on the glass surface vanished within 1 min.