Electroluminescence is an optical and electrical phenomenon in which a material emits light in response to the passage of an electric current or to a strong electric field.

The typical structure of an OLED electroluminescent device is based on one or more organic semiconductor layers provided between two electrodes.

The organic materials can be very small molecules or polymers.

If we cut an electroluminescent strip vertically we will find first with the negative electrode or cathode, usually metal. Here we find the luminescent material (1) and followed by the positive electrode or anode (conductive material).This conductor would be covered with a transparent protective layer (2).The combination of electrons and holes in a material, typically a semiconductor, generates the release of the electrons energy as photons. These photons are light (3) projected and visible.

Its most important technical features are:

• They can illuminate large surfaces.
• Uniform illumination.
• Very low power consumption.
• No radiation emission.
• Very small sizes and/or flat.
• Flexible.
• Indoors and outdoors working.
• No vibration.
• There are a lot of colours.

Its most common applications are:

• Lighting panels of vehicles or aircraft.
• Keyboard panels or electronic panels.
• Displays.
• Signs and posters or billboards.
• Decoration.
• Road signs and vests.

VAC would be the abbreviation of Volt Altern Current which would be translated Volts of alternating current. The difference between VDC is that its sinusoidal oscillation achieving a more efficient energy transmission.

The alternating current is the energy that we receive in our homes, it is generated in the power plants by means of alternators.

The intensity of this type of current varies with time, and changes direction 50 times throughsecond (50hz). The generated voltage changes in the form of sine wave so it is not constant.

In the image:

1. Current by pulsations.
2. Direct current (DC).
3. Alternating current (AC).
4. Variable current.