OLED – A future-shaping innovation?

Widescreen flat screens have hardly established themselves in living rooms when the next display generation is already in the starting blocks. Your name: OLED.
Its features: ultra-flat, high-resolution and made of plastic.

But what exactly is OLED and why will it oust the currently popular flat screens from the market in the foreseeable future?

About the technique:

OLEDs (Organic Light-Emitting Diode) are based on organic semiconductors that light up as soon as voltage is applied. A distinction is made between small molecules and long-chain polymers.

The structure is compared to a LCD very simple – at least in theory:

OLED technology works with multiple layers of organic semiconductors and organic dyes, which together form a layer that is only a few nanometers thick. Wafer-thin electrical contacts lie between these two layers. If current flows, as mentioned above, the electrical charge carriers give their existing energy to the molecules, which are thereby stimulated to produce light. When the color molecules fall back from the excited state, they emit a flash of light. Depending on the level of excitation, a specific color is produced. Everyone pixel An OLED display consists of one OLED for each of the three primary colors red, green and blue. The basic colors can be finely graded by the different states of excitation.

In practice, however, this turns out to be a little more complex, because the diodes are extremely sensitive to moisture and oxygen and therefore have to be encapsulated behind glass, which also limits the production size. The same purity criteria apply to processing as in the semiconductor industry. There is currently a religious war between engineers over whether it is better to use short or long plastic molecules for the super displays of the future. Currently, 98 percent of the products are small molecule OLEDs.

 

The history:

It all started with the development of the first LED in 1962. These achieved a light output of 0,1 lumen per watt. After several stages of development, this yield increased to 100 lumens per watt.
In 1979, researcher Chin Tang discovered electroluminescence. Working with solar cells, he observed a blue glow from organic material.
In 1987, Tang and Van Slyke introduced the first thin organic film light-emitting diodes. With these OLEDs, small organic molecules were vapor-deposited onto the carrier material in a vacuum.
In 1990, the year in which electroluminescence from polymers was discovered, Cambridge Display Technology developed a process that mixed long-chain plastics in a liquid Phase to be printed onto an electrode of the OLED using an inkjet-like method (polymer OLED or PLED). This laid the foundation for large organic displays.

To the future:

Even today, OLEDs are already being used, e.g. B. for mobile phone displays, car radios, etc.

Also conceivable for the future would be use as large-area room lighting, televisions and monitors.

According to the current state of the art, however, OLED technology still has a few weaknesses. One of these weaknesses is the short lifespan of about 30.000 hours, which is only half of today's flat screens. In addition, some pixels age faster than others. This results in differences in brightness.

However, with OLEDs we are getting closer and closer to the technology in science fiction films such as Dune or Andromeda, in which messages are presented on ultra-flat e-papers. They also offer high resolutions, strong contrast values ​​(1.000.000 : 1) and a "feather-light" weight, e.g. B. only 2 kg for a TV.

 

To the present:

At the end of January 2009, Sony launched the XEL-1, an 11-inch OLED TV for around EUR 4.300 (as of the end of January) on the German market!

                     

But the competition doesn't sleep either! LG announced its first OLED TV back in 2008. Everything then came together at the IFA 2009 and the first 15 incher was presented. However, it can only be bought in Korea and should cost the equivalent of just under 2000 euros before other markets are planned to be added in 2010. That the topic is taken very seriously at LG can also be seen from the fact that they have founded their own LG OLED company in this regard, which should focus even more on the new display generation.

Far ahead of the competition is Mitsubishi, which presented a huge OLED television with a screen diagonal of 2010 m (equivalent to 3,78 inches) to the public for the first time at the ISE 149 in Amsterdam. The display impresses with a Resolution of 1.088 x 640 pixels, with each pixel being approx. 3 mm away from the next pixel. The new "television" is also impressive when it comes to brightness: a measurement resulted in 1.500 candelas per square meter, which means that it is many times brighter than current LCD models. According to Mitsubishi, however, this version should not get into the living room. The 149 incher is clearly aimed at the advertising market, e.g. B. for shopping centers. However, an official launch before 2011 is out of the question.

Advantages and disadvantages:

Advantages:

• • Low power consumption (e.g. 45 watts, protects batteries in laptops, mobile phones, etc. thanks to their intrinsic luminosity) > as a result: OLED screens generate less heat than LCDs

• • Thinner screens (e.g. 3mm)

• • Strong contrast values ​​(1.000.000 : 1, comparison Plasma: 10.000 : 1)

• • Avoidance of motion blur as it processes image signals about 100 times faster than LCDs (0,001 ms vs. 2,0 ms)

• • • High resolution (e.g. Samsung SDI 1600 × 1200 pixels

  )

• • Lightweight (e.g. two kilograms for a TV)

• • Low production costs (because there is no background lighting, material costs for the light-emitting layer are therefore eliminated. In theory, they can be easily printed onto a carrier material, i.e. in a few years there could be printers that can print OLEDs inexpensively)

• • A perfect picture from almost every angle (170 degrees)

Disadvantages:

• Not a very long service life (30.000 hours, 10 years with an average of 8 hours operating time), some pixels age faster than others, result: differences in brightness

• Metals used rust, anode material breaks if bent too often. However, manufacturers promise to fix this in the coming years.

• No market development at the moment, since every application that could be realized with an OLED today can also be realized with other flat display types.