Technology Explained: OLED Display and How it works

What is the OLED technology all about? OLED panels are made from organic (carbon based) materials that emit light when electricity is applie...

What is the OLED technology all about?

OLED panels are made from organic (carbon based) materials that emit light when electricity is applied through them. Since OLEDs do not require a backlight and filters (unlike LCD displays), they are more efficient, simpler to make, and much thinner - and in fact can be made flexible and even rollable. OLEDs have a great picture quality - brilliant colors, infinite contrast, fast response rate and wide viewing angles. OLEDs can also be used to make OLED lighting - thin, efficient and without any bad metals.

OLED materials have been discovered back in 1960, but only in the past 20 years or so have researchers started to actually work on the technology

How do OLEDs work?

The main component in an OLED display is the OLED emitter - an organic (carbon-based) material that emits light when electricity is applied. The basic structure of an OLED is an emissive layer sandwiched between a cathode (which injects electrons) and an anode (which removes electrons). Modern OLED devices use many more layers in order to make them more efficient and durable, but the basic functionality remains the same.

How an OLED panel is made?

An OLED panel itself is made from a substrate, backplane (electronics - the driver), frontplane (the organic materials and electrodes as explained above) and an encapsulation layer. OLEDs are very sensitive to oxygen and moisture and so the encapsulation layer is critical.

The substrate and backplane of an OLED display are similar to those of an LCD display, but the front plane deposition is unique to OLEDs. There are several ways to deposit and pattern the organic layers. Currently most OLED displays are made using vacuum evaporation, using a Shadow Mask (FMM, Fine Metal Mask) to pattern. This is a relatively simple method but it is inefficient (a lot of material is wasted) and very difficult to scale up to large substrates. Some OLED materials are soluble, and these can be deposited using printing methods - mostly ink-jet printing. This technology is not commercialized yet, but OLED makers hope that ink-jet printing may be a scalable, efficient and cheap way to deposit OLEDs.

OLED materials

There are several types of OLED materials. The most basic division is between small-molecule OLEDs and large molecule ones (called Polymer OLEDs, or P-OLEDs). All commercial OLEDs today are SM-OLED based. P-OLEDs had great promise as they are naturally solution processable (and so can easily be used in InkJet printing and spin-coating fabrication methods) - but P-OLEDs are no longer popular as the performance was never up to par with SM-OLEDs. Intensive research is being performed to develop efficient solution-processable SM-OLEDs. OLED emitter materials are classified as either fluorescent or phosphorescent. Fluorescent materials last longer but are much less efficient than phosphorescent materials. Currently most OLED displays use phosphorescent emitter materials - except for the blue color which is still fluorescent as the lifetime is still not good enough. Universal Display Corporation is pioneering PHOLED research, holding the basic patents in this area.

Challenges

The are still many challenges facing the OLED industry. Here's a list of some of the major ones:

»Material lifetime and efficiency (especially of the blue material)
»Soluble OLED material performance and production processes
»Flexible OLED encapsulation
»Better backplane materials for flexible OLED
»Scaling of evaporation processes for direct-emission OLEDs beyond Gen-6

OLED technology today

The leading AMOLED producer today is Samsung, who's making around 300 million displays a year, and is still expanding production capacity - of mostly smartphone-sized flexible AMOLEDs. LG Display is the second largest producer, but LG is currently focused on WRGB (WOLED-CF) 55" to 77" OLED panels for OLED TVs. LG is producing around a million OLED TV panels each year, and expanding its capacity. LGD is also building flexible OLED production fabs.

Besides LG and Samsung, other players, including China's BOE, Visionox and Everdisplay are also starting to produce AMOLEDs, and other display makers such as Sharp and Japan Display aim to start producing OLEDs by 2018.

source:oled-info.com