OLED technology works in a similar way to conventional diodes and LEDs; however, instead of using layers of n-type and p-type semiconductors, OLED uses organic molecules to produce electrons and holes. A simple OLED is made up of six different layers, which all combine to make light.
On the top and bottom of a simple OLED, there are layers of protective glass or plastic. The top layer is called the seal, and the bottom layer is called the substrate. There are negative and positive terminals in between. These are sometimes referred to as the cathode and anode, respectively. Then, there is the emissive layer, found in between the cathode and anode layers, and the conductive layer.
The emissive layer is where light is produced, and it is placed next to the cathode. To make the OLED light up, a voltage is attached across the anode and cathode. When the electricity starts to flow, the cathode receives electrons from the power source, and the anode loses them. This creates a situation where the added electrons make the emissive layer negatively charged, while the conductive layer becomes positively charged.
When a hole, or lack of electron, meets an electron, the result is a brief burst of energy in the form of a light particle, or photon. This process, called recombination, happens many times a second and produces continuous light, as long as the current keeps flowing. OLEDs produce colored light when a color filter is placed beneath the top or bottom layer.