The ‘tunnel of light’ in the basement of the Audi Electronics Center in Ingolstadt is a rather dark place – until it comes to casting light on the situation. The floor is gray, the curtains have black drapes and only in the middle there are three specimens brightly lit in various shades of yellow and red. The room is like the stage of a theater, with Stephan Berlitz, Head of Innovations Lighting/ Lighting Electronics at Audi, as the stage manager.
Berlitz is one of the development engineers who have helped put Audi in the lead in modern automobile lighting technology. LED daytime running lights and headlights are development milestones; the next step forward will be OLED. Displays using this technique have already reached series production maturity in the electronic industry. Berlitz and his team cooperate closely with Audi Design on utilizing OLEDs as exterior lighting for the automobile.
OLED stands for “organic light emitting diode”. Unlike LEDs, which consist of semiconductor crystals, they are organic polymers with the properties of semiconductors. Only a few nanometers thick, the paste-like material occupies the space between an anode and a cathode. These both have an electrically conductive coating. Because they are only a few thousandths of a millimeter thick, all these materials can be transparent if necessary.
Two glass plates with a flat polished surface enclose the assembly and make it air- and water-tight. The resulting sandwich, just over a millimeter thick, is held in a metal frame. If a low voltage is applied, photons are emitted in the electrical field and the surface is illuminated. The thinner the layer, the greater the brightness. Various polymers can be used to obtain different colors.
Several OLEDs can be placed one behind the other for mixed color effects, since they are transparent. White light is obtained by adding the colors together.
Stephan Berlitz demonstrates a rear light that his team has built up for the Audi Q7. Inside it, the light comes from four small red OLED plates aligned next to one another. Eight flat segments make up the curved yellow strip for the flashing turn indicator.
“This homogeneous visual effect would not be possible with today’s LEDs,”Berlitz explains. “These are individual points of light that need additional optical devices – reflectors, optical conductors or scatter optics. OLED surfaces are themselves the source of light, and the thin plates also look attractive. They weigh little, light up extremely fast, develop only a small amount of heat, last for several tens of thousand hours and don’t consume any more energy than conventional light-emitting diodes. OLEDs suit Audi perfectly because they combine high-end technology, maximum precision and super design!”
The Audi roadmap for introducing OLEDs to series production will take several years to put into effect. At the current level of development, the new diodes only withstand low currents and the acceptable temperature range ends at about 80 degrees Celsius. OLEDs will make an appearance as rear lights in the relatively near future; for brake lights, which have to be about five times brighter, a few more years will elapse. But Berlitz can also visualize white OLEDs being used for daytime running lights and side lights.
The biggest target of all – especially for Audi’s designers – are three-dimensional OLEDs. The first prototypes are now appearing as part of a project with public support. They are fascinating: delicate, almost weightless ring-shaped sources of light, installed on various levels in the rear light units of an Audi TT.
Free forms can perhaps be obtained by means of an intermediate solution – arranging the small plates three-dimensionally. Clusters of this kind could be located anywhere on the body, as seen on a model of the future Audi R8 OLED concept. It has strips consisting of hundreds of triangular OLEDs on its sides, back and inside the car. “My design department colleagues have transformed the entire car into a source of light!” says Berlitz. This will permit the car to be identified in a whole series of ways that can be constantly varied.”
The ‘swarm’ – the third exhibit in the tunnel of light, is another scenario for the future. The rear end of the car is transformed into a large illuminated surface, with innumerable small points of light flickering like a swarm of fish and following the car’s movements. When the driver turns right, the swarm moves in the same direction, when he or she applies the brakes, the ‘fish’ rush forward, and the faster the car is driven, the more hectic the swarm’s movements. In this way the OLEDs tell the driver behind actively just what the car is doing.
The ‘swarm’ uses OLEDs in a technical display, with a matrix made up of a large number of pixel-size units that can be energized separately. The OLED swarm too combines the attractive with the practical, or as Berlitz puts it: “It looks sensational but it’s also a definite safety feature!”