New manufacturing process to make OLEDs Bilig

A new procedure can be extremely thin conductors applied to glass.

Experts at the Fraunhofer Institute for Laser Technology (ILT) In Aachen are working with Philips for a process to organic light emitting diodes (OLEDs) To make much larger and less expensive – and therefore suitable for the mass market. OLEDs are considered the basis for a new generation of lamps: large surface, any malleable and flexible to integrate into the architecture. The hook: A flat disk with a diameter of eight centimeters currently costs around 250 euros.

The high price is justified, particularly in complex manufacturing process. An OLED lamp has a sandwich-like layer structure: a flat bottom electrode, about a range of intermediate layers and the actual light layer of organic molecules. Finally there is a second electrode made of a special material indium tin oxide (english indium tin oxideShort ITO). Together with the lower electrode, the ITO layer, the job of supplying the OLED molecules with electricity and thereby to bring to light.

The problem: The ITO electrode is not conductive enough to power evenly distributed over a larger area. The result: Rather than give a homogeneous light effect, takes the brightness in the center of the area light from visible. "To compensate, they bring additional conductors on the ITO layer on" Christian Vedder, project manager at the ILT. "These tracks are made of metal and distribute the current evenly over the surface so that the light is homogeneous."

Typically, the conductor tracks are applied by an energy-intensive evaporation process: "In this method, only a maximum of ten percent of the deposited metal can be used most of the rest, including chemical etchant must be disposed of consuming." Says Vedder. Unlike in the new method: Instead of vapor-much material and most of it to remove it, the scientists bring only exactly as much metal as is needed. First, they put a mask film on the surface of the ITO electrode. Where later the tracks will be in the form of micrometer fine slots are introduced. On this screen, the researchers, a thin metal film of aluminum, copper or silver – the metal, should consist of the tracks.

Then a laser is moving at a speed of several meters per second from the conductor pattern. The metal melts and vaporizes, the vapor pressure ensures that the melt droplets are forced through the fine cracks in the mask on the ITO electrode. As a result of extremely thin conductors occur. With up to 40 microns, they are much narrower than the 100 microns wide traces, which can be produced using conventional technology.

"In the laboratory we were able to show that our method works," says Vedder. "The next step is to move the process along with Philips in industrial practice and to develop a systems engineering, you can use to the tracks on a large scale to raise cost." In two to three years of the new laser technique could be ready for practice.

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