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A display supplied by Merck consists of flasks, a chromatography column, and a vaporizer. The display demonstrates the basic principle that is used to create the extremely pure starting materials for organic light-emitting diodes. © Vitra Design Museum 2013; photo: Ursula Sprecher
A typical OLED structure (left) is based on small molecules that are thermally evaporated in multiple layers between the anode and cathode in a vacuum. Only two layers, usually consisting of different polymers, are needed for solution-based OLED technology (right). The polymers are processed from solutions and use special adopted coating technology (inkjet printing or spin coating).

OLEDs – Structure and Function

OLEDs – organic light emitting diodes – have a simple structure. They consist of organic semiconductor small molecules or polymers mounted on a substrate of glass or flexible film between conducting electrodes. When a current flow between the electrodes, pairs of electrons and holes are formed, which generates excitons. They return from the excited state to the ground state by emitting light. The molecular structure of the semiconductors used determines the color of the light emitted. In a component based on small molecules, each OLED material has its own characteristic function.

Nothing to stop flexible displays and lighting
OLEDs made from small molecules or polymer materials normally only need a single substrate. The advantage: OLEDs can be manufactured as flexible, paper-thin layers turning virtually every surface into a display or light source. In the future this will enable new kind of applications beyond traditional display and lighting.