Macroelectronics.org will start a series of posts on OLEDs. Stay tuned.
OLEDs, or organic light-emitting diodes, are thin films of organic molecules that generate light when electricity is applied.OLEDs have a potential to provide shaper, crispier, and clearer display than today’s LEDs (Light-emiting diodes) and LCDs (Liquid crystal displays).
An OLED, with different layers of material, is only about 100-500 nanometers thick.It typically consists of five functional layers: substrate, anode, two organic layers (both conducting layer and emissive layer), and cathode.The substrate, usually made of glass or clear plastic, is used to support the OLED.When electrical current passes through cathode and anode, emissive layer receive electrons from the cathode, and the anode removes electrons from conductive layer.Once an electron leaves conductive layer, there is an “electron hole”.Then, extra electrons from emissive layer jump to conductive layer to fill electron holes.When an electron combines with an electron hole, there is a drop in the electron energy level and such an energy drop is released in form of visible light (e.g., photons).The color of the light produced depends on the material of the organic layer.Therefore, a color OLED display can be made by using different layers of organic material that emit different colors.
The following animation illustrates how OLEDs work: