"For the future I know"

OLEDs as the next-generation light source

Four generations of lighting technology OLLA / Philips
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They are flat, light and only about a millimeter thick. They have an extremely long service life, consume little energy with high luminosity, enable diffuse illumination and can emit color-tunable light: organic light-emitting diodes, or OLEDs for short, or organic light-emitting diodes. So far they are already being used in cell phones, laptops or televisions. Scientists at the University of Dresden, together with European colleagues, now want to develop highly efficient white light-emitting diodes that could possibly serve as light sources of the future.

According to the researchers, OLEDs with their outstanding properties could compete with conventional light sources such as light bulbs or neon tubes in ten to fifteen years.

"Our goal is a life span of 10, 000 hours - ten times longer than that of a normal light bulb - and a light output of 50 lumens per watt, " says Peter Visser of Philips, project manager of OLLA.

Olla develops better OLEDs

More than 20 of the leading European companies and research institutes, including scientists from the Institute for Applied Photophysics of the TU Dresden, have joined forces to form the project OLLA, in order to further develop the technology of organic light emitting diodes (OLEDs). The aim of the research group, which includes European universities and research institutes as well as industrial companies such as Osram, Philips and Siemens, is the further development of light emitting diodes into a light source with a long service life and high energy efficiency.

"OLEDs are the ideal office lighting, in my opinion. They can be mounted flat on the ceiling and diffuse diffused light throughout the room ", explains Professor Karl Leo from the Institute of Applied Photophysics at the TU Dresden the advantage of the organic light source. The fields of application of the novel lighting technology are manifold. Conceivable, for example, would be transparent LEDs, with the help of windows could be converted into light sources. display

Model from nature

Scientists from nature have copied the principle of action for the luminous organic diodes. The basic principle of luminescence is observable, for example, in the firefly. Researchers have analyzed the underlying fundamentals and found that some organic materials have semiconductor properties and are therefore suitable for the transport of electrical charges.

Organic light-emitting diodes consist of semiconducting organic layers that are only about 100 nanometers thick and lie between two electrodes, one anode and one cathode each. When electrical voltage is applied to the electrodes, current flows through the organic layers and they emit light. By chemically different layers can produce desired colors.

The Institute of Applied Photophysics is researching a method in which OLEDs are manufactured under exclusion of air. Under vacuum, a wafer-thin organic layer is evaporated on a glass substrate.

The OLLA project, which runs until 2008, has a budget of almost 20 million euros. It is financially supported by more than half of the Sixth Framework Program of the European Commission.

(Technical University Dresden, 24.11.2005 - DLO)