Today LED (Light Emitting Diode) lights have taken place of most of the light bulbs. LED is a semiconductor diode which emits lights with the help of electric current. LED bulbs are used for many purposes such as indicator lights in various electronic device, flashlights and area lighting device. LED bulbs can be found in various shapes and colors. The color of emitting lights depends on the composition and condition of the semi conducting materials used. It can be green, red, yellow, infrared or ultraviolet. There are interesting applications also which uses LED bulbs such as UV-LEDs for the sterilization of water and disinfection of devices and to enhance the photosynthesis in plants as a grow light.

Now, a new type of LED has been made called OLEDs (Organic Light Emitting Diode). OLEDs are those LED in which the emitting layer material is an organic compound. In these organic compounds you will find conjugated pi bonds and with the help of these bonds they work as a semiconductor. It can be a small organic molecule in a particular crystalline phase. Some LEDs are made with the help of polymers and they are called PLEDs.

LEDs, OLEDs and PLEDs can be used in different ways such as:

- Where flexible display is needed.

- In various light sources.

- In the decoration of walls or any type of surface area.

- In some types of luminous cloths.

There are many types of LEDs and these are miniature, high power, flashing and multi-power LEDs. Every type of LEDs has different purpose to serve. Miniature LEDs comes in different sizes and used in building LED panels, dashboard backlight, etc. Flashing LEDs are used making attention required indicators. Flashing LEDs have inbuilt multivibrator circuit which makes them to flash. High power LEDs are used in home lighting system or for making LED lamp. And the multi-color LEDs are used where two different color light is needed in one single bulb.