A composite layer of atomic-layer-deposited Al2O3 and graphene for flexible moisture barrier

Abstract

In this study, a composite layer of atomic-layer-deposition-grown Al2O3 (ALD Al2O3) on chemical-vapor-deposition-grown graphene (CVD graphene) was fabricated for encapsulation of an organic light-emitting diode (OLED). NO2 functionalization was adopted to improve the nucleation and film quality of the ALD Al2O3 on CVD graphene, and the resulting Al2O3 on NO2-functionalized graphene exhibited increased film density and decreased porosity and roughness compared to that without functionalization; these improved properties satisfy the requirements for encapsulation layers. In addition, the water vapor barrier property of the Al2O3 and graphene composite layer was improved compared with that of a single Al2O3 layer; a single graphene layer did not exhibit the barrier property because of inherent defects. According to the laminate theory, the calculated water vapor transmission rate of graphene in the composite layer was about 2 × 10−3 g/m2·day, which is much greater than that of the single graphene layer without Al2O3 because of the combinational effects of the Al2O3 layer. Furthermore, the permeability of graphene was almost unchanged before and after the application of bending stress because of its mechanical durability and flexibility. This ALD Al2O3/graphene composite is expected to be a promising encapsulation layer for future flexible OLED devices.