Article last updated on: Feb 25, 2018

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

For flexible panel, rigid glass is obviously not an option, and in such panels producers use different techniques, collectively referred to as Thin Film Encapsulation, or TFE. TFE is a multi-layer film, made from alternating organic and inorganic layers.



Most organic layer TFEs use an inkjet printing process. Inkjet printing is usually associated with micro-scale OLED deposition, but the technology can also be used to deposit organic TFE materials. Kateeva (an OLED inkjet printing pioneer) has launched an encapsulation inkjet printer system towards the end of 2014, and in 2016 the company announced that it secured the "vast majority" of available TFE orders, and its customers include the world's largest flat-panel display makers in three key Asia regions.

Kateeva says that inkjet printing can achieve exceptional large-area uniformity, and it is the only technology with sufficient accuracy that offers the capability to coat and pattern the edges in a single step. Kateeva produces and markets its own encapsulation materials, but the systems can also use materials from other makers.

The inorganic TFE material deposition can be done in different methods, and several companies are targeting this market. The incumbent technology for the inorganic TFE deposition is Plasma-enhanced chemical vapor deposition (PECVD) which seems to be currently used by both Samsung and LG Display.

Atomic Layer Deposition (ALD), which is a modification of the basic CVD process, can also be used to deposit these materials, and it seems that this newer technology is gaining ground in the TFE market as it enables thinner and more uniform films. Several companies develop ALD-based OLED encapsulation systems, and as early as 2012 Beneq shipped a large-area flexible OLED ALD system to a "leading Asian customer". In 2017 Encapsulix also announced it supplied mass production ALD-TFE equipment to a leading Asian AMOLED producer.

LG Chem truly flexible OLED lighting panel photo

Further reading

Latest OLED Encapsulation news

OLEDWorks uses BASF barrier as a planarization layer in its new Brite 3 OLED lighting panels

A few days ago OLEDWorks announces its new OLED lighting series, the Brite 3 OLEDs, which include OLEDWorks' first flexible OLED lighting panels, branded as BendOLEDs.

BASF's Coatings division announced that OLEDWorks uses the company's flexible barrier solutions in its Bright 3 family of OLED panels (both flexible and rigid). OLEDWorks uses BASF materials as planarization layer to enable highly reliable thin-film encapsulation.

AUO developed a transparent 13" OLED for AR applications

Taiwan's AU Optronics (AUO) developed a 13-inch 100 PPI transparent OLED display, specifically for AR applications. This is a highly-transparent display - with 68% transmittance.

AUO transparent OLED prototype

AUO 6" transparent OLED prototype (2011)

To achieve such high transparency, AUO optimized the TFT array layer stack, the OLED cathode pattern and the encapsulation. This is the first transparent OLED AUO has developed since 2011. It will discuss this new display at SID Display 2018 - and will hopefully demonstrate it as well.

OLED Handbook

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.

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.