Thin-film encapsulation of Al2O3 multidensity layer structure prepared by spatial atomic layer deposition

Aluminum oxide films deposited by spatial atomic layer deposition have been used for thin-film encapsulation of organic light-emitting diodes. In this study, a multidensity layer structure consisting of two Al2O3 layers of different densities was deposited at varying ozone flow rates. The structure improved moisture permeation barrier characteristics, as confirmed by the water vapor transmission rate (WVTR) measurement. The lowest WVTR of the multidensity layer structure was 5.3x10(-5) g m(-2) day(-1), which is two orders of magnitude lower than that of a reference single-density Al2O3 layer. This improvement can be attributed to the location mismatch of paths in the film for atmospheric gases, such as oxygen and water, due to different layer densities. High-resolution transmission electron microscopy and x-ray photoelectron spectroscopy confirmed the multidensity layer structure's superior characteristics as an encapsulation layer due to a location mismatch of the paths for oxidative species between the two layers.