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.

LG Chem truly flexible OLED lighting panel photo

Further reading

Latest OLED Encapsulation news

OLED Ink-jet printing market situation, early 2018

Many OLED producers believe that Ink-Jet printing of OLED emissive materials is the best way to achieve lower-cost OLED TV production, and to enable OLEDs to compete in the medium part of the TV market. Ink-Jet printing is an efficient process (less material waste compared to evaporation) and it can be very quick as well. The main drawbacks of inkjet are the limited resolution and the need for soluble emissive materials which are less efficient compared to evaporation ones.

A Kateeva OLED ink-jet printing system

These challenges are being overcome, and it seems that at least four groups (in Korea, Japan and China) are charging forward towards mass production of ink-jet printed OLEDs. Ink-jet printer makers and soluble material suppliers are also optimistic ink-jet printing commercialization will soon be here as the material performance gap is diminishing.

The EU LEO project developed efficient and cost-effective OLED lighting technologies

Leo project logoIn 2015 the EU launched a 3-year €4 million OLED lighting project, the LEO project (Low-cost / energy Efficient OLEDs) that had an aim to develop efficient and cost-effective bendable OLED lighting technologies. The project consortium included Osram, and Cynora.

A month before the project officially ends, the partners updated on their progress. For this project, the partners develops several technologies, including low-cost metal foils integrating OLED anodes and possibly backside monitoring printed circuits, smart OLED top-electrode architectures and light out-coupling solutions and a novel thin film top-encapsulation strategies. These technologies together increased the light output by 50% while providing better surface scratch resistance.

OLED Handbook

The Holst Centre developed and demonstrated a new barrier for foldable OLEDs

The Holst Centre is demonstrating a new optimized encapsulation (barrier) layer for foldable OLED panels. The new barrier is made from an organic layer sandwiched between two layers of silicon nitride (SiN). These are standard materials, but by optimizing the stack design the researchers at the Holst Centre were able to control its mechanical properties and create a much more flexible barrier.

Foldable OLED demonstrator with a new barrier layer (Holst, Nov 2017)

The Holst researchers used an organic material that can withstand 400 °C and can be applied by slot-die coating. This allows the SiN layers to be deposited at 350 °C, improving their quality and ability to prevent water penetration. The Holst tested the OLED prototypes that use the new barrier for 1,000 hours (in accelerated lifetime testing) and no black spots appeared, even after 10,000 folding cycles (bending radiud 0.5 mm).

Graphene-based barrier demonstrated as a possible solution for flexible OLED encapsulation

Graphene is the world's most impermeable material, and as the material is also transparent, flexible and ultra-thin it makes sense to adopt graphene as an encapsulation layer for next-gen OLED displays. A UK project led by Cambridge University researchers have set out in 2015 to develop such a solution, and the researchers now report that they have demonstrated a viable graphene solution comparable to existing commercial OLED encapsulation technologies.

Graphene encapsulation research, CPI 2017

In its pure form, graphene is permeable to all gases, but 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 stacked to create a multi-layer coating. The researchers say that a ~10 nm barrier layer that includes 3-4 layers of graphene (with AlOx in between) is an effective solution for OLED displays. The 10 nm layer maintains a high optical transparency (>90 %) and high flexibility.

Idemitsu Kosan and Toray to co-develop OLED materials

Japan-based OLED material maker Idemitsu Kosan announced a new partnership with Toray Industries to co-develop OLED materials.

Toray and Idemitsu will mutually utilize the OLED materials, technology and expertise that both companies possess, and will cooperate in the development of new materials and material evaluation. The two companies will also jointly use their evaluation facilities and production facilities. Both companies hope that this collaboration will accelerate OLED material development and enable lower cost production.

The Fraunhofer FEP, NSMAT and MSSMC developed an OLED on a stainless steel substrate

The Fraunhofer FEP institute, in collaboration with Nippon Steel & Sumikin Materials (NSMAT) and Nippon Steel & Sumitomo Metal Corporation (NSSMC), developed a new OLED lighting prototype that is made on a stainless steel substrate.

OLED on stainless steel prototype (Fraunhofer, NSMAT, NSSMC)

The researchers say that a stainless steel substrate has several advantages compared to glass or plastic - it has excellent thermal conductivity and excellent barrier properties. The lighting panel features an extremely homogenous OLED light, thanks to the planarization layer developed by NSSMC. The prototype panel was produced at the Fraunhofer's R2R research line.

CSoT orders OLED deposition equipment from AP Systems for its 6-Gen flexible AMOLED fab in Wuhan

AP Systems announced that it has received orders for OLED deposition equipment from CSoT for the company's 6-Gen flexible AMOLED fab in Wuhan that is currently under construction.

AP Systems ELA system photo

AP Systems said that the whole order is worth $60.65 million and the equipment will be delivered starting in September 2017 until October 2018. AP Systems did not disclose the equipment list, but the company's main products are laser annealing equipment (used to produce LTPS substrates), laser list-off equipment and OLED encapsulation tools.

IHS: The OLED encapsulation material market will grow at a 16% CAGR to reach $233 million by 2021

According to IHS, the OLED encapsulation material grew 4.7% in 2017 to reach $117 million. IHS expects the market to grow at a 16% CAGR to reach $233 by 2021.

OLED encapsulation material market forecasts (IHS, 2016-2021)

The market growth rate will increase as new OLED fabs begin operation in China and Korea. IHS categorizes OLED encapsulation materials into metal, frit glass, TFE and hybrid. The metal type is mostly used for OLED TVs, in which IHS expects the fastest growth in terms of substrate size. Glass encapsulation will remain strong but will lose market share in the future.

Truly sees large demand for PMOLED displays, to dramatically increase capacity by next year

OLED maker Truly Semiconductor, based in Hong Kong, sees a large increase in PMOLED demand in the near future, and the company is executing an ambitious PMOLED capacity expansion plan.

Truly is currently operating two production lines: the P1 and P2 lines, both 2.5-Gen and with a monthly capacity of 625K and 1.25M pcs (Truly counts its capacity as per 1" displays). Truly has set out to build two new production lines. The P3 line which is a 2.5-Gen line with a capacity of 3.13 million 1” panels monthly is almost ready and will start mass production by the end of the month.

UBI Research sees PECVD as the in-organic TFE equipment of choice for flexible OLED production

UBI Research says that as OLED makers are diverting all efforts into flexible OLED production, thin film encapsulation (TFE) is gaining in popularity. Between 2017 and 2021, TFE will be applied to about 70% of all OLED panels in production. The OLED encapsulation equipment market will generate $11 billion in sales.

PECVD oled encapsulation market share (UBI, 2017-2021)

TFE encapsulation started out as a complex technology that required 11 layers and was slow and expensive. Recent advances allowed OLED makers to reduce the number of layers to just 3 and increase productivity and yields and so lower the production costs. Some film OLED makers opted for hybrid encapsulation (which uses a barrier film) but TFE seems to have become the technology of choice.