In 1990 researchers from the Cavendish Laboratory in Cambridge (UK) discovered that a thin layer of the conjugated polymer Poly(p-phenylene vinylene) sandwiched between a hole-injecting electrode (transparent ITO) and an electron-injecting electrode (e.g. aluminium) yielded light emission under voltage bias. The injected electrons and holes meet in the bulk of the polymer film and emit light as the result of radiative charge carrier recombination. OLEDs, organic light-emitting diodes using thin semiconducting organic film, are very energy-efficient and can be produced using printing techniques such as inktjet printing and screenprinting.
Unlike conventional light sources, OLEDs can be made into flat, or even flexible, thin sheets, which offer completely new design possibilities for lighting, advertising, and traffic-sign applications: light tiles with adjustable colours, transparent light film, luminous wallpaper and clothing, etc.
Next to the polymer based electroluminescent devices, also inorganic electroluminescent inks are being studied at IMO-IMOMEC, which resulted in the creation of the spin-of company Lumoza NV (www.lumoza.be).