Edison demonstrated his version of the incandescent light bulb in 1879, and light bulbs have roughly resembled that prototype ever since. Even the energy-efficient, squiggly shaped CFL bulbs that have recently begun to replace the familiar pear-shaped ones look like they belong to the same family. As do the stranger-looking, even more expensive, and even longer-lasting LED light bulbs that have started to turn up in stores.
The changing story – and shape – of the light bulb doesn't end here. Although fluorescent and LED light technology permits a range of lighting shapes, OLED lighting promises to change the entire light-bulb paradigm, with lights that are not bulbs at all, but slim, flat, flexible panels – even whole walls of light that can change color and luminosity. OLEDs are also touted for their light quality and environmental friendliness. So far, however, most OLED lighting has not gone beyond a standard 15-cm-sized rigid panel and is not yet mass produced on an affordable scale. So, OLEDs are not going to "take over" right away, but they are definitely coming on, especially in Europe.
That impetus is demonstrated by projects such as the OLED100.eu consortium, which has the overall goal of developing the necessary technologies for efficient OLED applications for the general lighting industry in Europe.1 The consortium includes lamp manufacturers such as Philips, Novaled, and Osram.
And there is the TOPAS (Thousand Lumen Organic Phosphorescent Devices for Applications in Lighting Systems) 2012 research project, which is "focused on developing innovative material and component architectures as well as new production machines for lighting solutions with highly efficient OLEDs."2 This project is funded by the German Ministry for Education and Research (BMBF) with OSRAM, BASF, Philips, and Aixtron.
Below is a sampling of what some OLED companies in Europe are doing now with regard to solid-state lighting.
Dr. Kai Exner, Senior Manager for OLED Materials at BASF notes: "The focus of BASF's activities is the development of phosphorescent blue emitters. For OLED lighting, red, green, and blue emitters are needed to generate white light. Phosphorescent emitters are necessary to achieve high energy efficiency because they are four times as effective in converting electrical energy into light as fluorescent emitters. Thus far, good red and green emitters are available in the market, but an efficient blue emitter with good color quality and especially long lifetime is the indispensible and still missing piece of the puzzle." This development is being accompanied by work on complementary materials such as hosts and blockers that need to be fine tuned to fit the emitting material.
Novaled in Dresden, Germany, has been a materials and technology provider in the OLED arena for more than a decade. Although the company serves customers in the display and lighting industries (Philips, for example, is a lighting customer), Novaled recently branched out into the luxury luminaire business. Its lighting brand is trademarked Liternity, and the first product to be introduced is the Victory desk lamp, which features four embedded ultra-flat OLEDs in an ultra-strong carbon-fabric base. The Victory lamps, so-called because the two arms form the V for Victory, are coated with several layers of clear lacquer to provide a "3-D" look (Fig. 1). The lamps will become available at selected retailers in the U.S., Europe, and United Arab Emirates this fall at a price yet to be announced.
Fig. 1: The Victory luminaire demonstrates the type of high design concept that OLEDs make possible. Source: Novaled.
Novaled's Senior Product Manager, Sven Murano, also addressed some of the current manufacturing challenges. "To make an OLED wallpaper is not primarily just a size problem. Currently, most OLEDs are still being processed on rigid glass substrates and there has not been any product-ready solution with flexible substrates yet. Thus far, only prototypes with limited lifetimes have been shown and one has to expect that no commercial flexible OLED lighting product will appear at least within the next 3–5 years. (For more on the future of OLED manufacturing and flexible backplanes, see the articles "Clearing the Road to Mass Production of OLED Television" and "Beyond Amorphous Silicon: New Developments in High Mobility Backplanes" in this issue.)
"Concerning size," continues Murano, "people are already starting to manufacture on Gen 2 substrates (~ 30 x 40 cm2), and tool concepts for significantly larger motherglasses are available." However, at this point the individual panels (that get cut out of the larger motherglass) are somewhere in that standard 15-cm range. This is for two reasons: "The transparent electrodes are not conductive enough to distribute the OLED current evenly over a larger size and the production yield goes down exponentially with size, so the larger you get the better you need to master the process in order to keep the yield up."
In August, Osram announced the opening of an OLED pilot-production facility in Regensburg, Germany. The facility, which currently employs 220 people, required an investment of 20 million Euros ($28.9 million). OSRAM says that transparent OLED panels will be manufactured there.
The biggest challenge in OLED lighting for companies anywhere in the world, according to Mike Hack, General Manager of OLED Displays for Universal Display Corp., is increased efficiency and lifetime. "We're always pushing for that," he says.
In the January issue of Information Display, we'll look at OLED and LED solid-state lighting advances in North and South America.