What is an OLED?

OLED (Organic Light Emitting Diodes) is a flat light emitting technology, made by placing a series of organic (carbon based) thin films between two conductors, that emit bright light when electricity is run through them. Because OLEDs do not require a filter to change colors (unlike LCD displays), they are more efficient, simpler to make, and much thinner. OLEDs have a great picture quality - brilliant colors, fast response rate and a wide viewing angle.

OLEDs are organic because they are made from carbon and hydrogen. There's no connection to organic food or farming - although OLEDs are very efficient and do not contain any heavy metals - so it's a real green technology.

Here's Kodak's description of OLEDs -

"OLED displays stack up several thin layers of materials. They operate on the attraction between positively and negatively charged particles. When voltage is applied, one layer becomes negatively charged relative to another transparent layer. As energy passes from the negatively charged (cathode) layer to the other (anode) layer, it stimulates organic material between the two, which emits light visible through an outermost layer of glass."

Where can I find OLED displays today?

Today you can find small (up to 3 or 4 inch) organic displays in many types of devices - mobile phones, A/V players, car audio systems, Digital cameras and PDAs. Lot's of companies are placing OLEDs in their products - Sony, Samsung, Nokia, LG, Microsoft, and others.

The main attraction today is the small size, the low power consumption and the great brightness. Obviously OLEDs carry a price premium over LCDs, but companies are using these displays more and more.

Samsung Galaxy S

AMOLED vs PMOLED

These terms relate to the driving method of the OLED display. Both PMOLED and AMOLED display use a TFT and line-scanning control: you change the pixels one line at at time, sequentially. In Passive Matrix (PMOLED) displays, the rows are turned off most of the time (between changes) and so you need to use more voltage to make the OLED pixels brighter (to compensate. If you have 10 rows, you have to drive them with 10 time the resolution). This is not efficient and limits the resolution (the number of rows). Active-Matrix (AMOLEDs) display use TFT with storage capacitors that retain the pixel information in the row at all times. AMOLED displays are more efficient and can be used to create large displays with high resolutions: but are more expensive to make than PMOLEDs.

So if you're looking for a TV, it'll probably be an AMOLED TV. PMOLEDs are used in mp3 players, secondary displays on cell phones, etc.

Small molecules vs Polymer-based OLEDs

OLED materials can be divided into small- and large- molecules. 'Small Molecules' OLEDs are more common today, with most displays using those kind of materials. Large Molecules (also called Polymer-based OLEDs, or P-OLEDs) are lagging behind in lifetime and efficiency specs. P-OLEDs might be easier to make, though, because they are more easily adapted for printing. Indeed, one can 'ink-jet-print' an OLED, which is a great way to make them. 

Fluorescent vs Phosphorescent OLEDs

OLEDs can also be classified based on another property of the material – whether it is fluorescent or phosphorescent (PHOLEDs). Originally fluorescent OLEDs were used, but PHOLEDs promise to deliver much more efficient displays.

The major company behind PHOLEDs is Universal-Display. They have recently stated that "virtually all" AMOLEDs use their technology - although only their red material is currently used (the other colors are fluorescent).

OLED technology today

Today OLED displays are used mainly in small (2"-4") displays for mobile devices such as phones, cameras and MP3 players. OLED displays carry a price premium over LCDs, but offer brighter pictures and better power efficiency - making it ideal for battery powered gadgets. You can see a list of gadgets with OLEDs here.

Samsung S8300 Ultra Touch

Making larger OLEDs is possible, but difficult and expensive. Sony has announced the XEL-1 11quot; OLED TV back in 2007 - but it was expensive at about $2,500 (they aren't producing it anymore). LG is also offering an OLED TV (the 15" EL9500) which is also expensive and isn't being mass produced. Real OLED TVs are only expected by 2012 or 2013.

OLED lighting panels should start to appear commercially within the next two years or so.

OLEDs can be used to make displays and lighting. Because OLEDs emit light they do not require a backlight and so are thinner and more efficient than LCD displays(which do require a white backlight).

LG Display 31-inch OLED prototype

OLEDs are not just thin and efficient - they can also be made flexible (even rollable) and transparent.

Flexible OLED lighting prototype

OLED vs LCD

OLED displays have the following advantages over LCD displays:

• Lower power consumption
• Faster refresh rate and better contrast
• Greater brightness - The screens are brighter, and have a fuller viewing angle
• Exciting displays - new types of displays, that we do not have today, like ultra-thin, flexible or transparent displays
• Better durability - OLEDs are very durable and can operate in a broader temperature range
• Lighter weight - the screen can be made very thin, and can even be 'printed' on flexible surfaces

The future - flexible and transparent OLED displays

It turns out that because OLEDs are thin and simple - they can be used to create flexible and even transparent displays. This is pretty exciting as it opens up a whole world of possibilities:

• Curved OLED displays, placed on non-flat surfaces
• Wearable OLEDs
• Transparent OLEDs embedded in windows
• OLEDs in car windshields
• New designs for lamps
• And many more we cannot even imagine today...

Several companies are working towards this, and we already got some pretty exciting prototypes. Hopefully these kind of displays will become available within a few years!

OLED disadvantages

OLEDs aren't perfect. First of all, these screens are currently expensive - although this should hopefully change in the future, as OLEDs has a potential to be even cheaper than LCDs because of their simple design.

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

OLEDs can also be problematic in direct sunlight, because of their emmissive nature. But companies are working to make it better. Samsung is producing in-cell touch panel displays (branded Super AMOLED andSuper AMOLED Plus) and Nokia has inlcuded a polarized filter in their Clear Black Displays.

Can OLEDs produce white lighting?

One of the more exciting attributes of organic displays is the low power consumption, and the ability to operate as a light source. OLEDs can produce white light, and can provide the bulb of the future - low power and thin designs (and no heavy metals). As OLEDs will also be flexible and transparent, this technology can truly be the light of the future.

Transparent white OLEDs by Philips

A lot of companies (Philips, OSRAM, GE, Lumiotec,Samsung, LG, UDC and others) are working towards OLED Lighting. OSRAM, Philips and Lumiotec already offer sample panels, but these are very expensive 'samples' and not real commercial products yet. Real products shold arrive by 2012, hopefully.