Fabrication of free-standing multilayered graphene and poly(3,4-ethylenedioxythiophene) composite films with enhanced conductive and mechanical properties.

Poly(3,4-ethylenedioxythiophene) (PEDOT)-based film has relatively high conductivity, flexibility, and transmittance. However, the improvement for mechanical strength and conductivity is still required to be adopted for commercial applications. Graphene, a one atom thick planar sheet of sp(2)-bonded carbon atoms, is considered as an ideal nanocomposite material for these purposes. In this study, we have developed PEDOT and graphene composite films, two-layered graphene/PEDOT and three-layered graphene/PEDOT/graphene, by using a spin-coating method. The conductivity of a 32 nm thick PEDOT film was improved more than twice by graphene deposition, while the high transmittance of the composite film was maintained over 90%. The mechanical strength of the PEDOT and graphene composite film shows 6-fold enhancement over the pristine PEDOT film. Because of the contribution of graphene layer for enhancing the mechanical strength, a 44 nm thick graphene/PEDOT/graphene could be obtained as a free-standing film by delaminating the graphene layer from the glass substrate under a weak base solution. These results imply that the graphene not only improves the conductivity and mechanical strength of PEDOT but also enables to produce a free-standing film which could find a variety of applications in the fields of organic electronic, sensors, and optoelectronics.