Flexible OLED Display

08/28/2014 14:46
OLED is an emerging display technology that enables beautiful and efficient displays and lighting panels. Thin OLEDs are already being used in many mobile devices and TVs, and the next generation of these panels will be flexible and bendable.
Different kinds of flexibility
When we talk about flexible OLEDs, it's important to understand what that means exactly. A flexible OLED is based on a flexible substrate which can be either plastic, metal or flexible glass. The plastic and metal panels will be light, thin and very durable - in fact they will be virtually shatter-proof.
It is estimated that the first range of devices to use a flexible display won't be flexible at all. While the manufacturer may bend the display or curve it around a non-flat surface, the final user will not be able to actually bend the device. Still it will have several advantages: these displays will be lighter, thinner and much more durable compared to glass based displays.
Second generation flexible OLED devices may indeed be flexible to the final user. Finally, when the technology is ready, we may see OLED panels that you can fold, bend or stretch. This may create all sorts of exciting designs that will enable large displays to be placed in a mobile device and only be opened when required.
Flexible OLED products
After years of research, in October 2013, Samsung announced the world's first product to use a flexible OLED display - the Galaxy Round curved smartphone. This is an Android 4.3 smartphone similar to the Galaxy Note 3, with the major feature being the 5.7" Full-HD curved (400 mm curvature radius) flexible display (samsung simply refers to it as a flexible Super AMOLED, strangely they are not using the YOUM brand).
LG is producing flexible OLED panels, 6" in size. It is expected that LG will also unveil their own smartphone (called the G Flex) with a flexible OLED towrads the end of 2013.
Initial capacity in both companies is low (a few hundreds of thousands of panels per month). Samsung's capacity is higher (they are using a Gen-5.5 line and LG is using a Gen-4.5 line) but this too will not be enough even for a single mass market phone. The company are probably waiting to see how consumers react to those new panels before they commit to increase capacity.
Samsung launched their YOUM flexible OLED panels in January 2013, showing some cool prototypes of curved and flexible OLED displays.
Some reports suggest that Apple is planning to use a small (about 1.5" in size) flexible OLED panel in their upcoming smartwatch device. This isn't confirmed yet and it will probably be a while before Apple chooses a flexible OLED for a mass market device.
Curved OLED TVs
Both Samsung and LG are now offering curved OLED TVs. These 55" panels are slightly curved and this offers a better viewing experience for someone who sits right in front of the TV as all the pixels are at the same distance from his eyes. Most people however, actually prefer a flat panel. In any case, as far as the OLED panel is concerned this isn't really a flexible OLED, it is a curved glass-based OLED panel.
OLED TV production capacity is extremely low and prices are very high. Samsung's KN55S9C for example costs $8,997 while LG's 55EA9800 is even more expensive at $9,999. Both panels are 55" in size and offer Full-HD resolution. Reviews of those TVs have been spectacular, with all reviewers saying that OLED TVs offer the best picture quality ever.
Flexible OLEDs research
While LG and Samsung seem to be leading the race towards flexible OLEDs, many other display makers such as AUO, Sony, Toshiba, Philips and others are also developing this technology. Subscribe to the OLED-Info newsletter to stay updated on flexible OLEDs and other OLED news!
Flexible OLED challenges
Fabricating a flexible OLED display is very challenging. The two major challenges are the backplane and the encapsulation. According to reports, Samsung is still using LTPS for their plastic based panels, and the production process for LTPS is too hot for the plastic substrate (it will melt). Samsung currently deposits the LTPS transistors on glass and the glass is later delaminated. LG Display is using an Oxide-TFT which should be easier to produce on a flexible substrate.
Samsung's current encapsulation technology is Vitex's multi-layer technology which is very slow (the panel has to enter the evaporation chamber 6 times). Some companies are working on single-layer barriers and better encapsulation processes, but these haven't been scaled to mass production yet. Samsung is said to be evaluating UDC's UniversalBarrier technology and Veeco's FAST-ALD.
Flexible OLED lighting
OLEDs can also be used to make white lighting panels. OLED is a diffuse area lighting source with unique characteristics. While OLED lighting is still in its infancy, many believe that flexible OLED lighting panels may provide designers with a new lighting source that will create stunning designs.
Several companies unveiled flexible OLED prototype in past years. The closest one to production seems to be LG Chem. The company currently plans to start mass production towards the end of 2013. LG Chem's first batch of flexible panels (seen in the photo above) will be 210x50 mm in size and will feature a 4,000K color temperature, 73 lumens flux, 55 lm/w and a high CRI (90).


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Subham's Electronics Circuits World Shyamnagar, West Bengal, India chatterjee93subham@gmail.com