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An Brief introduction to OLED displays


What is an OLED?

OLED stands for Organic Light-Emitting Diode is a flat light emitting technology that uses LEDs in which the light is produced by organic molecules, These organic LEDs are used to create what are considered to be the world’s best display panels, it made by placing a series of organic thin films between two conductors. When electrical current is applied, a bright light is emitted. OLEDs are emissive displays that do not require a backlight and so are thinner and more efficient than LCD displays-which do require a backlight. So it is a simple design - which brings with it many advantages over other display technologies. OLEDs enable emissive displays - which means that each pixel is controlled individually and emits its own light (unlike LCDs in which the light comes from a backlight unit). OLED displays feature great image quality, bright colors, fast motion and most importantly, and very high contrast. Most notably, “real” blacks (that cannot be achieved in LCDs due to the backlight). The simple OLED design also means that it is relatively easy to produce flexible and transparent displays. OLED displays are not just thin and efficient - they provide the best image quality ever and they can also be made transparent, flexible, foldable and even rollable and stretchable in the future. OLEDs represent the future of display technology!

OLED Device Structure

The OLED structure is an organic emitter placed between two electrodes. But in order to create efficient and long-lasting devices, commercial OLEDs use several intermediate layers, like electron transport and blocking layers. The whole organic stack is placed between the electrodes, and this whole structure is deposited on the substrate (like glass or plastic) and the display backplane (driver electronics). Some OLED displays on the market make dozens of different layers, one on top of the other, layer upon layer.

OLED Production Processes

Currently, nearly most of OLED displays on the market are produced by using an evaporation-based process in which the OLED materials are deposited in a vacuum chamber. This has proven to be a great way to make OLEDs, but the process has its limitations - mainly material waste and high cost.

It’s necessary to develop next-generation deposition processes to enable more efficient production. One example is ink-jet printing, which makes use of soluble OLED inks that can be deposited using huge printers. This process is faster than the current evaporation process, and has almost no waste of materials. While there are still some challenges to overcome, it is expected that printed OLEDs will start entering the market soon.

OLED Emitter Material Generations

The first OLED devices used so-called fluorescence emitters (1st-gen emitters). These are relatively stable and easy to produce compounds, but their internal efficiency is limited to around 25% - only a quarter of the energy is translated into light.

2nd-generation OLED emitters, called phosphorescence OLEDs, dope these emitters with heavy metals (usually iridium) which enables the internal efficiency up to 100%. As of today, very efficient red and green phosphorescence OLEDs are available on the market and most OLED displays make use of these to create highly efficient emitters.

An efficient and long-lasting blue emitter material has proven extremely hard to produce, and still need struggling to develop this material. Any much-anticipated success in doing so would surely have a dramatic effect on the power efficiency of OLED displays. While one option is to develop a blue phosphorescence OLED, there are also 3rd and even 4th generation materials (TADF and Hyperfluorescence) OLED technologies which show great promise.

Testing and organic of the OLED

Testing an OLED device involves simultaneously measuring its electrical and optical properties to generate a current-voltage-luminance (IVL) curve. This allows the power efficiency and brightness to be characterised. Lifetime testing is also important to ascertain how quickly an OLED will degrade over extended use.

The future of OLEDs seems bright, OLED technology is still an emerging technology, and many avenues are still open for new materials to be found and new processes to be developed that could further enhance OLED displays.

OLEDs are organic because they are made from carbon and hydrogen. OLEDs are very efficient and do not contain any bad metals, so it's a real green technology.

OLED disadvantages

OLEDs aren't perfect. First of all, it costs more to produce an OLED than it does to produce an LCD - although this should hopefully change in the future, as OLEDs has a potential to be even cheaper than LCDs because of their simple design (some believe that future OLEDs will be printed using simple ink-jet processes).

OLEDs have limited lifetime (like any display), that was quite a problem a few years ago. But there has been constant progress, and today this is almost a non-issue.

OLED white lighting

OLEDs can be used to create excellent light source. OLEDs offer diffuse area lighting and can be flexible, efficient, light, thin, transparent, color-tunable and more. OLEDs enable new designs and these devices emit healthier light compared to CFLs and LED lighting devices.

Several companies, all over the world are developing OLED lighting technologies. The market is still at its infancy, with very high prices as production volume is low. We hope that the future will see an increased adoption of OLED lighting, although currently there are many challenges yet before mass production begins.