Large Area Graphene Transfer And Its Application In Flexible Touch Screen

Graphene is a single atomic layer of sp2 bonded carbon atoms arranged in a two dimensional hexagonal lattice. The discovery of graphene has attracted enormous interest and leads to intensive studies over the worldwide, due to its extraordinary properties, such as high transparent, high carrier mobility, high conductivity,outstanding mechanical strength which are vital for practical application. Since the first well-ordered monolayer graphene was obtained by mechanically exfoliated highly oriented pyrolytic graphite, but its small size is limited to fundamental studies. Different ways to prepare graphene have been developed by so far, such as chemical oxidation and reduction, epitaxial growth of SiC, chemical vapour deposition (CVD) on metal foil substrate such as Ni, Ru, Ir, Cu, etc. Note that CVD method is the most widely used to produce large-area, high-quality, single-layer graphene, which can satisfy the need of industrial application involved in touch screen, solar cells, light-emitting diodes,photodetector and molecular separation. For the practical application, the graphene grown on metal should be transferred completely onto the target aim substrate. Up to now, there is existing a challenge in transferring graphene grown on the metal foil to the target substrate (Si/SiO2, glass, PET) without cracks damage the quality of graphene and residues leaving on the surface of graphene. In this study, we presented a new transfer method that one-step directly transferred large area graphene to the target substrate with high quality. Moreover, it is application in capacitive-type touch screen based on graphene film. The detailed contents are followed:(1) We demonstrate one-step directly transferred large area graphene film grown on copper foil to transparent ethylene vinyl acetate/poly ethylene terephthalata (EVA/PET)substrate with high quality by hot-roll-pressing transfer technique. The graphene was characterized by OM, SEM, Raman, XPS, UV-vis. These results proved the graphene can be completely transferred on EVA/PET without any polymer residues.In an effort to low the sheet resistance of G/EVA/PET, the wet-chemical doping was used. We found that the G/EVA/PET film have the sheet resistance as low as 200 Q/sq with optical transparency of 86.7% by the optimized doping conditions.(2) The mechanical bendability of doped G/EVA/PET film was in vestgated by tracking change of sheet resistance after being bended at different curve radius and bending times. The sheet resistance of G/EVA/PET film is almost unchanged (changing rates of ?0.01 %) after being bended at curve radiuses from 2 to 90 mm. The G/EVA/PET film could be bent over 10000 cycles at a radius of 2 mm without increase of the sheet resistance (changing rates of ?0.02 %). These results demonstrate the excellent bendability of graphene/EVA/PET film for bendable electronics.(3) Based on the superior properties of G/EVA/PET film, the capacitive-type touch screen was fabricated. Our results demonstrate that graphene film based touch screen can work well under bending state.