OLED displays are very sensitive to oxygen and moisture, and the need to protect the displays is one of the major challenges of this next-generation display technology. First generation OLED displays were protected with a glass barrier, but glass is not easily flexible and so cannot be used in flexible OLEDs. Flexible OLEDs are today encapsulation with a thin-film encapsulation layer made from both organic and in-organic materials, and companies are searching for better OLED encapsulation technologies.
Graphene is the world’s most impermeable material, and so the idea of using graphene as a barrier layer for OLED has been around for a while. In 2015 the UK launched a collaboration project called Gravia to develop graphene-based encapsulation, and the project’s team has now reported their results.
Graphene is permeable to all gases in its pure form, but of course real life materials are never entirely pure and defects and holes harm the material’s permeability. The new research used ALD and CVD to create large-area high-quality single-layer graphene sheets which were than stacked to create a multi-layer coating. Multi-layers are required as a single graphene sheet is never perfect. The researchers say that a ~10 nm barrier layer (or about 30 graphene layers) is an effective solution for OLED displays. The 10nm layer maintains a high optical transparency (>90 %) and high flexibility.
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