High performance metal microstructure for carbon-based transparent conducting electrodes

In this work, a metal busbar microstructure is introduced to decrease the effective sheet resistance of both graphene and carbon nanotube films to a value suitable for use as transparent conducting electrodes (TCEs). The proposed busbar architecture, implemented with Cu, theoretically can reduce the sheet resistance by a factor of 1000, while yet limiting the optical absorption to 4%. Experimental sheet resistance and optical transparency data are presented for two metals with differing contact resistance (Pd and Cu) and for mono- and multi-layer graphene as well as nanotube films. It is found that the metal busbar microstructure decreases the sheet resistance by a factor of 8 and 70 on graphene and nanotube films respectively, a sufficient resistance reduction to enable utilization as a TCE. The contact resistance between the metal grid and carbon film is believed to limit the ultimate performance. The metal busbar microstructure provides a viable route to the use of carbon films in photovoltaic and display applications.