The color of the light of a LED is determined by the chemical composition of the activated material: red light is based on aluminum gallium arsenide (AlGaAs); blue light comes from indium gallium nitride (InGaN); green light is produced by aluminum gallium phosphide (AlGaP). White light can be created in two ways: by combining red, green and blue chip (RGB LED) , or applying a coat of phosphor into the blue chip transforming the blue light into a full spectrum white light (Phosphor based LED). This one, the echnology Green Ray Led Lighting uses, has a better relation between quality and price and is used today by 90% of the white light LED products.
LEDs are small, usually with a surface of less than a square millimeter. The LED used for lighting applications is mounted on a DIP package or an SMD circuit board, electrically joined to the circuit board; a plastic element or silicon provides protection and, in some cases, acts as a lens and/or transport for the phosphor. LEDs generate heat when an electric current flows through them, although they produce significantly less heat than incandescent or fluorescent light bulbs. In order to keep the output as well as the LED lifetime, the heat must be dissipated using a thermal management system, usually a heat dissipator.
Generally, optical elements are used to handle the light produced by one LED or a group of LEDs.