OLED - The revolution of illumination?!
The diodes consist of several different layers of materials – each of them has to fulfil a specific task: starting with the carrier material, nowadays most of the time glass, in select cases also metal, all the way to the encapsulating cover glass, ten different layers are nothing unusual.
Among them are, in part, transparent electrode materials, electron-transporting materials, and the actual organic emitter materials in which light is generated. The individual materials are applied in very thin layers – some a few nanometres thin – in large areas on the carrier substrate (for instance pre-treated sheets of glass). This way, an evenly luminescent series of layers is created in which each individual emitter layer can luminescence.
For the manufacturing, either small molecules or polymer materials are utilised. At present, small molecules are being used predominantly. In comparison to polymer materials, small molecule OLEDs last longer and are more efficient. OLEDs generate light in the visible range exclusively.
Depending on the combination of the individual layers, they emit monochrome light, i.e., light of a single colour, or white light that consists of several light colours. In this, warm-white and cold-white colour tones are possible. The light emitted is radiated by the OLEDs diffuse, homogenous, and almost Lambertian, meaning it is radiated evenly in all directions, in a single direction (in case of intransparent OLEDs) or in two directions (in case of transparent OLEDs).