Flexible and transparent supercapacitor based on ultrathin Au/graphene composite electrodes

Large-area monolayer graphene by chemical vapor deposition as electrode in electronic devices always suffers from shortages of low conductivity and high contact resistance. In this work, we demonstrate a composite electrode by depositing a continuous and homogeneous ultrathin 7-nm Au film on monolayer graphene with low average sheet resistance of 24.6 Omega/square and high transmittance of 74.6% at 520 nm. The excellent properties of the composite electrode are attributed to the suppressed Au Volmer-Weber growth mode of the ultrathin Au film by the organized hexagonal carbon lattices of graphene. Rigid supercapacitor based on the composite electrode exhibits a capacitance of 81.5 mu F/cm(2) at the scan rate of 0.1 V/s, which is 17 times higher than the device based on monolayer graphene. Flexible supercapacitor based on the composite electrode can be bending at curvature radius of 2 mm and with slight performance decrease over 1800 bending cycles.