The use of graphene as a transparent electrode has already been demonstrated in a variety of flexible optoelectronic devices, including touch-screen sensors, organic light-emitting diodes and organic photovoltaic devices. In addition, graphene’s outstanding gas-barrier properties are intensively investigated to develop an encapsulation layer for various flexible display and energy devices. Preventing reactive gas species such as oxygen or water is important to ensure the stability and durability of organic electronics. Although inorganic materials have been predominantly employed as the protective layers, their poor mechanical property has hindered the practical application to flexible electronics. The densely packed hexagonal lattice of carbon atoms in graphene does not allow the transmission of small gas molecules. In addition, its outstanding mechanical flexibility and optical transmittance are expected to be useful to overcome the current mechanical limit of the inorganic materials. In this talk, we reported the measurement of the water vapor transmission rate (WVTR) of large-area graphene films synthesized by chemical vapor deposition (CVD). The WVTR was measured to be as low as 10-4 g/m2 per day. We also showed that the graphene-passivated organic field-effect transistors (OFETs) exhibited excellent environmental stability as well as a prolonged lifetime even after 500 bending cycles with strain of 2.3%.

The use of graphene as a transparent electrode has already been demonstrated in a variety of flexible optoelectronic devices, including touch-screen sensors, organic light-emitting diodes and organic photovoltaic devices. In addition, graphene’s outstanding gas-barrier properties are intensively investigated to develop an encapsulation layer for various flexible display and energy devices. Preventing reactive gas species such as oxygen or water is important to ensure the stability and durability of organic electronics. Although inorganic materials have been predominantly employed as the protective layers, their poor mechanical property has hindered the practical application to flexible electronics. The densely packed hexagonal lattice of carbon atoms in graphene does not allow the transmission of small gas molecules. In addition, its outstanding mechanical flexibility and optical transmittance are expected to be useful to overcome the current mechanical limit of the inorganic materials. In this talk, we reported the measurement of the water vapor transmission rate (WVTR) of large-area graphene films synthesized by chemical vapor deposition (CVD). The WVTR was measured to be as low as 10-4 g/m2 per day. We also showed that the graphene-passivated organic field-effect transistors (OFETs) exhibited excellent environmental stability as well as a prolonged lifetime even after 500 bending cycles with strain of 2.3%.