Flexible and transparent reduced graphene oxide and silk fibroin composite films with kilo-ohm square resistance

A general method of producing flexible transparent conducting thin film composed of reduced graphene oxide (RGO) and silk fibroin (SF) is demonstrated; the production is accomplished via spin-coating followed by the process of chemical reduction and transferring. Adjusting the amount of spin-coating performed produces RGO/SF-based (GSF-based) composite films with resistances ranging from 22 k Omega/sq to 1.3 k Omega/sq and visible light transmittance from 80% to 15%. Due to the exceptional mechanical behaviour of RGO and SF, the obtained composite films exhibit excellent flexibility, so that the composite film still maintains its performance even when heavily bent. The highlighted tensile property shows a breaking stress higher than 60 MPa and a fracture strain of approximately 17%. This simple, effective and low-cost approach yields novel, flexible, transparent and conductive composite films that possess numerous potential applications in flexible photovoltaic devices.