A white LED (Light-Emitting Diode) is typically made up of several components that work together to produce white light. The main components are:
Semiconductor Chip: The heart of an LED is a semiconductor chip made of a material such as gallium nitride (GaN) or indium gallium nitride (InGaN). The specific composition of the chip determines the color of the emitted light.
Phosphor Coating: To create white light, blue light-emitting diodes are commonly used. These blue LEDs are coated with a layer of phosphor material. The phosphor absorbs some of the blue light and re-emits light at longer wavelengths, covering a range of colors including yellow and red. The combination of blue light and the re-emitted yellow and red light appears as white light to our eyes.
Encapsulation: The LED chip and phosphor layer are encapsulated in an epoxy resin or silicone material, which protects the components from damage and helps shape the light output.
When an electric current is applied to the LED, electrons and electron holes within the semiconductor material recombine, releasing energy in the form of photons. In the case of a white LED, the blue light emitted by the LED chip interacts with the phosphor coating. Some of the blue light passes through the phosphor, while a portion is absorbed. The absorbed blue light excites the phosphor particles, causing them to emit light at longer wavelengths. The combination of the blue light and the re-emitted yellow and red light results in a mixture of colors that our eyes perceive as white light.
It's worth noting that there are different methods and variations in the construction of white LEDs, including variations in the phosphor materials used. Some white LEDs also utilize different techniques like multiple-color chips or color-mixing schemes to produce white light. However, the principle of combining blue light with additional colors to achieve white light remains a common approach in white LED technology.