Flexibility and durability of a graphene electrode as a flexible transparent electrode and effect of hard coating layer

We synthesized graphene electrodes for a flexible transparent conductive electrode. The graphene was grown with the rapid thermal chemical vapor deposition, and then transferred on polyethyleneterephtalate using the roll-to-roll transfer system. The flexibility and durability of the graphene electrode were investigated with outward/inward bending, stretching, and bending fatigue tests. The effect of the hard coating layer on the flexibility of the graphene electrodes was evaluated. The graphene electrodes showed sheet resistance of ?130 /square and transmittance of 85%. The outward bending tests indicated that the graphene electrodes were bent to a bending radius of 3mm, however, the flexibility was decreased due to the brittle hard coating layer. The thermal conductivity images using scanning thermal microscopy clearly exhibited cracks in the graphene after bending. The inward bending tests showed that the resistance of the graphenes remained constant until a bending radius of 2mm, regardless of the hard coating layer, indicating that the graphene electrodes have excellent mechanical stability in compressive stress. In the uniaxial stretching test, the graphene without a hard coating layer showed small changes in resistance until 4% tensile strain. The outer bending fatigue test showed that the graphene electrodes can withstand 10,000 bending cycles.