Fabrication of transparent, flexible conducing graphene thin films via soft transfer printing method

As a unique type of soft building block, graphene oxide (GO) dispersions are easy to process to produce flexible transparent conductive films (TCFs). Developing methods to produce large size GO with layered structure is the key for these applications. Here, we demonstrate a method to prepare ultra-large graphene oxide (UL-GO) sheets (up to ~100 μm in lateral size) in aqueous media, which are then transferred onto polyethylene terephthalate substrates through soft transfer printing method. The as produced UL-GO films have layered architectures and exhibit high electrical conductivity and transparency after the chemical reduction by using hydroiodic (HI) acid. The produced flexible TCFs deliver sheet resistance ranging 0.3-17 kΩ/sq with optical transmittance ranging 72-95% depending on the thickness. The technique proposed to produce flexible TCFs is inexpensive and tunable for mass production.