Highly transparent conducting graphene films produced by langmuir blodgett assembly as flexible electrodes

This paper reports the development of an efficient method to produce transparent conductive graphene films layer-by-layer on a flexible substrate based on the Langmuir Blodgett (LB) assembly technique. Monolayer ultralarge graphene oxide (UL-GO) sheets of average lateral size greater than 300 μm² are prepared by repeated centrifugation of as-prepared GO aqueous dispersion. GO films having different numbers of GO layers are fabricated using the LB method while controlling the LB trough surface pressure and pulling speed of the substrate from the dispersion. GO films are chemically reduced at 90°C using hydrogen iodide (HI) acid, followed by chemical doping treatments. The sheet resistance values of the graphene thin films on a PET film are 1.8 and 1.1 kω/sq for 2 and 4 graphene layers, respectively, with a transparency of higher than 90%, which are sufficient for many useful applications. It is found that the thicker the film, the higher the conductivity; and vice versa for the transparency of the graphene films.