Optimization of Al2O3/ZrO2 nanolaminate structure for thin-film encapsulation of OLEDs

We report thin-film moisture barriers based on Al2O3/ZrO2 nanolaminates grown by ALD for an encapsulation of OLEDs. In order to optimize the moisture-barrier performance of the nanolaminates, the most important factors affecting the performance were sought by measuring WVTR of the nanolaminates via an electrical Ca test. We found out that both the number of interfaces in the nanolaminates and the thickness of ZrO2 in a unit layer were responsible for the performance. By optimizing the nanolaminate structure, the moisture-barrier performance was enhanced up to 350% from a single layer of the same thickness. The WVTR of 30-nm-thick optimized nanolaminate barrier was 2 × 10−4 g/(m2 day) or less at ambient condition. A storage-lifetime measurement of an OLED with a 100-nm-thick encapsulation layer showed that it could exceed 70,000 h if stored at ambient condition.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Al2O3/ZrO2 nanolaminate structure was optimized to show the lowest WVTR. ► Number of interfaces in the nanolaminate is very important for lowering WVTR. ► It is crucial for the ZrO2 thickness in nanolaminate to be kept <4 nm for lowering WVTR. ► The WVTR <2 × 10−4 g/(m2 day) is achieved at the total barrier thickness of 30 nm.