OLED (Organic Light Emitting Diodes) is a flat light emitting technology, made by placing a series of organic thin films (usually carbon based) between two conductors - and these films light up when electrical current is applied. OLEDs are used to make display and lighting panels. OLED displays are thinner, more efficient than LCD displays, and they offer a far better image quality.
One of the most exciting features of OLED displays is that they can be made flexible. Can you image foldable phones that open to become tablets, TVs that can be rolled up when not in use and lighting panels that wrap around round pillars? Flexible OLEDs can enable all of that, and more.
One of the major problems with those organic materials is that they are very sensitive to oxygen and moisture. This means that OLEDs need to be protected - as even a single water or oxygen molecule can harm the OLEDs.
Thin Film Encapsulation (TFE)
With regular - rigid - OLED panels, the solution is simple - you can use a strong glass sheet. Glass is a great barrier, and it is widely used in the display industry and so easy to process. The glass used in current display and lighting panels is rigid and not very durable. So companies are looking for alternatives to standard glass encapsulation materials. Flexible OLED encapsulation is actually one of the major challenges towards cost effective mass production of flexible displays.
There are several technologies that enable thin-film encapsulation (TFE) suitable for flexible OLED displays:
- Vacuum Polymer Technology: developed at Vitex and bought by Samsung in 2010, this is the technology currently used by Samsung. It is a multi-layer barrier that is relatively slow to deposit as it requires several stages (SDC recently managed to reduce them from 6 to 3) and so Samsung is looking to replace it with a more cost effective solution.
- LG's Faceseal: LG's own encapsulation technology, this is a a multi-layered organic and in-organic film. LG Display currently uses Faceseal for both flexible OLED display and lighting panels.
- Atomic Layer Deposition (ALD): ALD can be used to quickly and efficiently deposit barrier films on flexible substrates. Several companies are developing OLED encapsulation systems based on ALD. One example is Veeco with their FAST-ALD tech (which they acquired in 2013 for $185 million) which is being evaluation by Samsung. Other OLED ALD developers include Beneq and Encapsulix.
- Ink Jet Printing: While ink-jet is usually associated with micro-scale patterning, it can also be used to accurately and efficiently deposit encapsulation layers. In November 2014 Kateeva launched an Ink Jet Printing based Encapsulation system, and already shipped a mass-scale system - presumably to Samsung Display.
- PECVD: Plasma Enhanced Chemical Vapor Deposition (PECVD) is another deposition technology that can be adapted for encapsulation barrier films. In 2015 Aixtron acquired PlasmaSi, a PECVD OLED encapsulation developer - and plans to incorporate those systems into its OLED deposition clusters.
- UniversalBarrier: This technology, developed by Universal Display (UDC), can be used to deposit single-layer encapsulation films. According to the latest update from UDC, the technology is not yet ready for mass production, but it is already being evaluation by Samsung Display.
- Flexible glass: Yes, it is possible to make flexible glass - which is a great barrier, but still not as durable as thin-film encapsulation materials. Corning for example is promoting its Willow Glass as a possible flexible glass encapsulation (and substrate) technology.
The latest OLED Encapsulation News:
- Meyer Burger ships an inkjet+PECVD OLED encapsulation system to an Asian customer
- Researchers develop a cheap and efficient MgO-based OLED encapsulation layer
- Veeco significantly reduces its ALD investments
- Both Samsung and LG to switch to ALD for in-organic TFE?
- Kateeva says it takes a commanding lead in the OLED TFE market
- Smithers Apex sees the barrier films for printed electronics market growing at CAGR of 25%
- Encapsulix announces a new 200 mm ALD system for flexible OLED encapsulation