Solution-processable reduced graphene oxide template layer for molecular orientation control of organic semiconductors

A reduced graphene oxide (rGO) film is first applied to a surface template layer to control the molecular orientation of crystalline organic semiconductors. The ultrathin and ultrasmooth rGO layer was successfully prepared on a substrate without a transfer process by spin-coating a carefully purified GO aqueous dispersion. This rGO layer exhibited a strong templating effect rivaling monolayer graphene, inducing a face-on orientation of copper phthalocyanine molecules leading to significant improvement of vertical carrier mobilities. The highly-conductive and transparent rGO film does not hamper charge transport at the interface and photoabsorption unlike conventional templating materials. This method can be widely used for vertical organic devices that require high carrier mobilities and strong photoabsorption/emission.