“Article available. Dispatch date next working day” is the good news for buyers who click on the symbol for OLED TV icon on one of the Sony European websites – for example, (www.sonystyle.co.uk). Finally, this 11-inch TV is now available in most of Europe – a year after the first models based on organic light-emitting diodes (OLEDs) were launched on the US and Japanese markets (see Plasteurope.com of 25.02.2008). The “bad news” is the price tag is upwards of EUR 4,000. LG is planning to introduce a 15-inch TV in summer 2009, and Samsung plans to launch an OLED TV with a larger screen some time in 2009.

Self-illuminating OLED screens have high resolution and crystal clear contrast from all viewing angles. Moreover, individual pixels switch off completely when reproducing black. That eliminates the disturbing effects of light scattering. But this is not the only advantage of screens without backlighting. OLED displays – regardless whether they are used for televisions or cell phones – need far less power than other technologies, yet have outstanding colour brilliancy. Moreover, their response time of one micro second is far faster than competing LCD technology. As well as being ultra-flat and allowing the manufacture of increasingly large surfaces, OLEDs are an energy-efficient method of lighting.

Given these benefits, the Center for Organic Materials and Electronic Devices Dresden (COMEDD) established by the Fraunhofer Society for Applied Research (www.fraunhofer.de) in October 2008 sees OLEDs as the future technology for displays and lighting. To conquer the mass market, though, affordability is an issue. In the lab, pixels can already be printed using a technique comparable to an ink-jet printer, but scale-up for serial production has not yet been achieved.

The vision of flexible screens or lights that can simply be rolled up and put away when not in use or that can be adapted easily to any given shape will only become reality when a material with adequate barrier properties is found to replace the glass in which light sources are currently encapsulated. The best packaging film presently available on the market has a barrier strength of 10^-4 g/m² per day. Lars Unnebrink of the technology centre of the Association of German Engineers (VDI, Düsseldorf; www.vditz.de) told Plasteurope.com that at least 10^-6 g/m² per day is necessary to protect these sensitive light sources from moisture. That is the research priority at present. In the longer term, the aim is to use lamination to protect the coated film – for example, polystyrene sulphonate (PSS), polyphenylvinyl (PPV) or polyaniline (PAni).

Considerable progress has been made with OLED displays since Pioneer first used them in car radios in 1999. Although figures from market research company DisplaySearch (Austin, Texas / USA; www.displaysearch.com) indicate that only about 2% of displays shipped use OLED technology, the market is expected to grow by 20% p.a. up to 2015. The sector is changing rapidly.

At present, around 90% of OLED displays are used in mobile telephones, where the switch from passive matrix technology to better-quality active matrix technology is proceeding rapidly. In 2007, the ratio was 50:50, but by 2008 it had reached 75:25 in favour of active matrix technology, according to Gerd Günther, marketing director at OLED producer Novaled (Dresden / Germany; www.novaled.com). Global sales of higher-value OLED displays increased from USD 67m to USD 300m between 2007 and 2008, with unit sales rising from 2.5m to 13.5m.

Although OLEDs are becoming established slowly but surely in the display market, and the first TV screens using this technology have caused a stir, there is still a good deal of R&D to be done. The biggest problem for the sector at present are high production costs, especially the cost of manufacturing sets with larger screens. Nevertheless, Günther sees enormous potential in the fact that the starting materials are far cheaper than those used in other technologies.

Around 19% of global power is currently used for lighting so that there is plenty of scope to make savings here. Extremely inefficient light sources are still widely used. Incandescent bulbs and halogen spots radiate a good deal of heat but relatively little light. Eckhard Heybrock, who is responsible for innovations to support the use of optical technologies at the VDI technology centre, says this is because there are still a number of technical problems with the far more efficient compact fluorescent lights and energy-saving bulbs, which currently account for around 70% of artificial light. For example, they are difficult to produce in small formats and they cannot be switched on and off quickly. However, a systematic changeover to energy-saving bulbs in Germany, for example, would reduce power requirements by about the output of one major power station. Switching to a new generation of lighting is therefore necessary.

One option is LED technology, which Heybrock claims is now advanced enough for general tasks such as street lighting and headlamps on cars. The aim is that LEDs should be used for one in three artificial light sources by 2025. And then, he says, there is the “even more promising vision" of OLEDs. One key argument is that OLEDs emit light across a wider area, recreating more of a daylight atmosphere that is kinder to the eyes.

Heybrock reports that the power of OLEDs now is roughly doubling every two years. He expects luminous efficacy to rise to 300 Im/W in the next few years. That is three times the efficacy of fluorescent strip. Incandescent lamps have a luminous efficacy rating of just 15 Im/W. The VDI technology centre currently assumes that OLED lamps will achieve levels of well over 100 Im/W, making them by far the most efficient light sources. The global market for this type of lighting is estimated at around EUR 13 bn by 2020.

However, a changeover to OLED lighting would require lighting manufacturers to adopt completely new market concepts. One possibility would be for manufacturers to offer packages such as retrofitting all traffic lights with the new OLED bulbs. Such packages could include service and maintenance by the supplier as well as initial installation. The switch would undoubtedly open up opportunities for the plastics converters, and perhaps even give small innovative businesses a chance to link up with OLED producers to market new ideas and products.

The switch to OLED lamps also would require completely new lighting concepts. “It is not simply a question of replacing lamp A with lamp B,” says Heybrock. Instead, the trick will be to provide the right amount of light and ensure that it is diffused correctly. One idea currently under development foresees installing OLED layers that react by sensor to changes in natural light in place of conventional ceiling lights in rooms with windows. The OLED lights would be transparent during the day and radiate an increasing amount of light at night. Illuminated wall coverings – which were dismissed as a pipe dream only a few years ago – now seem to be far closer to becoming reality.

First, though, a number of problems have to be resolved. For example, durability is currently too low according to Günther. At present, such lights burn for 5,000-6,000 hours – compared with a target of 20,000 to 30,000 hours. That level has already been achieved under lab conditions but not in industrial production. One prerequisite would be to improve the reproducibility of the manufacturing process. What’s more, costs are still far too high. The cost of products manufactured in the laboratory is 100 times higher than the target of around USD 100 per m². “All major lighting manufacturers in Europe and the US are working on this issue,” Günther stresses. However, he has also observed a certain reluctance to enter the market, as companies are wary of scaring off customers with products that are not yet ready for commercialisation.