Light leaves the lab

5 May 2011

An Osram employee feeds uncoated OLED substrates into the cleaning bath

How close are organic light-emitting diodes to becoming a widely-available, viable white light source? Richard Simmonds spoke to lighting designers, equipment manufacturers and researchers to find out

Talk to any lighting designer and you’ll discover they have an opinion about organic light-emitting diodes (OLEDs), the flat panel solid state light sources that perpetually seem to be on the brink of commercial use. Usually, the enthusiasm for the nascent technology will be palpable.

Jonathon Hodges is from Jason Bruges Studio, which specialises in interactive lighting projects that embrace cutting edge technology. He has used OLEDs in a couple of projects: “I hope we will see groundbreaking projects that use OLEDs in non-decorative applications in the next year or two. Within five years I’d hope to see them getting out into the higher end commercial interiors.”

Real applications

Similarly, Sam Neuman of Neuman Lighting Design is enthusiastic, but he is all too aware of the difficulties of using a light source that is really still in the research and development phase. “It’s very difficult to use unless you’re willing to invest significant R&D time. As a designer, you probably can’t afford to do that.

“I met an OLED guy for an update, and the technology seemed to be pretty much where it was a year ago. It has not moved on enough to make me think it has applications outside beautiful art installations at the moment.”

And beautiful art installations there are. Jason Bruges Studio worked on a project at the headquarters of Aston Martin in Warwickshire. “As part of the spectacle of purchasing one of their supercars, you get to go to the headquarters, have a tour and ‘meet’ your car,” says Hodges. “They throw open the doors to a reveal suite, and inside is an OLED chandelier that is designed to show off the particular finish that they have on the bodywork.”

Philips supplied the OLED devices for the project. “Philips mentioned to us that this was something they had coming up in a couple of years,” says Hodges, “and we’d been pestering them, asking to do something with OLEDs when they were produced in large enough quantities. In the end, they couldn’t make them fast enough for us. There are about 700 in the Aston Martin reveal.”

The second Jason Bruges project is Mimosa, a showcase project for Philips at the Milan Furniture Fair last year.

“Mimosa is a folding flower arrangement where each OLED petal of the flower moves as people pass by the sculpture.”

Hodges says: “For these two projects we were using OLED in a way that you couldn’t use any other light source. It brings a new aesthetic. There are quite a lot of fittings that are scratching the surface of what the technology can do.

Ingo Maurer has done a couple of things and there are lots of other people trying out some really crazy decorative ideas.”

State of the art

Establishing the state of the art in OLEDs can be tricky. There are R&D efforts worldwide - privately and publicly funded - that are all keen to be first to market with workable OLED products. OLEDs are available from the big manufacturers, but researchers will tell you that the technology is several years away from widespread application.

Lighting giants Philips and Osram demonstrate the peculiar state of the OLED market at present. Philips’ Lumiblade system became commercially available in April 2009, comprising an OLED module, a standard lighting panel and a socket and base system. OLED panels are available for commercial use, says the company, but as engineering samples.

Philips’ centre for OLED technology is Aachen in Germany, where it has opened an OLED production line and the Lumiblade Creative Lab. The purpose of the lab is to bring together luminaire makers, designers and other lighting industry professionals to become more familiar with OLED technology.

Kristin Knappstein, head of business creation for OLEDs, says: “The lab is not an abstract concept but a real workshop. The Creative Lab team offers advice and guidance as well as practical support, helping to progress projects beyond the design stage into a prototype or small-scale production.”

Osram, meanwhile, has Orbeos. Karsten Heuser, director and general manager, OLED, says: “Orbeos, which we produce in series production, has a lifetime of 5,000 hours.”

The company has also developed PirOLED and Airabesc, prototype luminaires that the company hopes will help “embed the technology among designers.” Heuser says: “OLEDs achieve an efficiency of 25 lumens per watt - even higher than that of conventional incandescent and halogen lamps. Laboratory samples already achieve an efficiency of 62 lumens per watt.”

Test of time

In the UK, OLED development - or more accurately PLED development (see box) - is led by Topdrawer (Thin Organic Prototypes: Design, Research and Applications With End-user Recognition), a business-driven project sponsored by the Technology Strategy Board and designed to take the technology out of the research lab and put it into a quasi-manufacturing environment.

The manufacturing process will be proved and tested at PETEC, the Printable Electronics Technology Centre set up in County Durham in 2009 with government funds. Participants in Topdrawer are Cambridge Display Technology; Thorn Lighting, part of Zumtobel; Tridonic; glassmaker Pilkington and Conductive Inkjet Technology.

Dr Geoff Williams is OLED group leader of Zumtobel’s LED division, and he has a clearer idea than most about where OLEDs are today. “The technology is emerging; there’s nothing that is available commercially that is application driven at this moment in time,” he says.

“It’s technologies that are very much at the demonstrator level. We will start seeing small volume, architectural lighting applications coming through in the next five years, but the market for volume applications will be in 2025-30.”

The reason for the lengthy timescales is the number of problems that have to be solved before OLEDs can become worthy replacements for more conventional light sources.

Williams cites just a few: increasing the size of OLED panels, boosting efficiency, improving lifetimes and ensuring repeatability in the manufacturing process.

Osram is focusing on similar problems. Heuser says: “The biggest challenge is the transfer of OLED panel processing to low-cost manufacturing technologies. Also, we have to increase efficiency, transparency, brightness and durability. The life of the components and their sensitivity to moisture and oxygen are crucial to their future use in lighting.”

Designers, too, are aware of the shortcomings of current OLED designs. Neuman says: “They’ve got to make it in bigger bits and they’ve got to make it more powerful. But it’s a new technology and we have to give it a chance.”

Williams agrees. Rather than focusing on the problems yet to be solved, he thinks it is wise to consider the unique qualities of OLED technology. “You have to look for alternative benefits and opportunities. Organic solid state lighting is low voltage DC, so why not consider using renewable energy generated locally to power the lighting?

“Instead of just talking about a luminaire, let’s talk about an application. If you’ve got a factory, the lighting could be standalone. Likewise for a commercial office building.”

On trend

Osram says this is one of a series of trends - from incandescent to efficient lighting, from older technology to LEDs and OLEDs, and from components to ‘solutions’.

Both designers and manufacturers emphasise the complementary nature of LEDs and OLEDs - and how OLEDs can supply diffuse ambient light alongside accent lighting from LEDs. Ingo Maurer demonstrated how both sources could work side by side in his Double C Future fitting shown at last year’s Light + Building exhibition.

Osram’s PirOLED is a hybrid luminaire comprising an aligned LED section in the base for directional light and five rotatable Orbeos panels for diffuse light.

The two sources may be complementary, but LED technology has had a bumpy road to market, something that everyone is anxious to avoid with OLEDs.

Williams says: “We mustn’t replicate the misinformation that was so familiar in the early days of LEDs. It will drive any potential customer away. Communication on the true status of the technology is imperative.

“OLEDs have got to open up a freedom of design for how you use lighting in an application, but there has to be a degree of standardisation on how the things fit together. There is a working group that is coming together to look at the challenges, and one of those has to be interconnectivity.”

Hodges is also optimistic: “Perhaps they will have learned their lessons and will get things organised before OLEDs hit the mass market.”

Neuman believes two other groups must be considered. The first is luminaire makers. “I think they have to make it very easy for the luminaire manufacturers to buy a kit of parts.” The second is installers. “Designers love contractor-bashing,” says Neuman, “but those guys have to resolve practical problems in the real world that we don’t have to deal with. If it’s easy for the contractor to install, it’s much more likely to have quick take-up.”

So, are OLEDs ready for prime time? Probably not, but it’s the perfect time for designers to steer the technology in a direction that will help ensure its future success.

OLEDs 101

OLEDs work by passing electricity from one flat electrode to another - at least one of which is transparent - through one or more layers of organic semiconductors. The entire assembly can be thinner than 1 micrometre and is mounted on a sheet of transparent material. At the moment the most effective substance for this ‘substrate’ is glass.

When a DC bias is applied to the electrodes, they emit negatively and positively charged ‘electrons’ and ‘holes’ that combine in the semiconductor layers causing a high-energy state called ‘excitation’. As the layer returns to its original state, the organic film emits light.

The colour of the light depends on the properties of the organic material. By stacking emitting layers in a single device the emission can be tuned to virtually any colour including white in various colour temperatures. Most white OLEDs contain red, green and blue layers.

A variation on the OLED theme is the polymer light-emitting diode (PLED), which is the focus of the Topdrawer project. Rather than multiple layers of organic materials, these devices have a single layer of white light-emitting polymer. In principle, this layer could be printed onto a glass or plastic substrate.

The promise of OLED

The attraction of OLEDs for lighting designers has a lot to do with its novelty. They envisage a world where large-area thin light sources are cheaply available in any size - and that is a reasonable prospect.

Sam Neuman believes OLEDs will open up totally new possibilities: “Because this stuff is flat, I was thinking: ‘How do you make flat three dimensional?’ and I thought ‘origami’.” His designs (see below) offer a glimpse into the possible future of lighting.

“What would also be nice would be relatively affordable short runs of bespoke flat lighting. Bespoke has become more common recently. You could do it with
LEDs, but it would be complicated and heavy.”

Osram says another game-changer will be large area transparent OLEDs, which it expects will appear as soon as next year. Philips, too, sees the possibilities and believes such panels could operate as windows during the day and mimic daylight in the evening.

But Hodges sounds a note of caution when he says: “All lighting designers have to find the right tool for the job. This is a very exciting development that will give us another great tool to use, but it’s never the one thing that will kill off everything else.”