Light Emitting Diode (LED) is a type of electronic components that convert electric energy into optical energy. Most LED Projects can send out lights within the range of infrared rays and blue rays. At present, Light Emitting Diode sending out purple rays and even ultraviolet rays has been invented. Besides, LED manufacturers also made a kind of white LED by coating a layer of fluorescent powder on a blue-ray LED. In the next section, we will discuss more details about color manufacturing technique of LED Street Light.
Light Emitting Diode made by different materials can emit photons with different energy. In other words, wavelength (color) of the light can be controlled by LED manufactures. In history, GaAs is the first materiel used to make LEDs. The minimal working voltage in forward bias is 1.424V. LEDs made by GaAs can only emit infrared rays. Another commonly used LED material is GaP. LEDs made by this material have a higher working potential: 2.261V, sending out green lights.
Based on these two types of materials, a new material construction GaAs1-xPx (x represents the ratio of phosphorus to arsenic) was used in the early LED industry. This new material construction realized multi-colored LEDs ranging from red rays to green rays. The wavelength (color) of the light is usually determined by the band gap (potential) PN junction, like red LED with a material construction of GaAs0.6P0.4, orange LED (GaAs0.35P0.65) and yellow LED (GaAs0.14P0.86). LEDs using material of arsenic, phosphorus and gallium were typically named “three elements LEDs”. Blue LEDs (GaN), green LEDs (GaP) and infrared LEDs (GaAs) are named “two elements LEDs”. The latest manufacturing technology is combining Al, Ga, In and N together as AlGaInN. LEDs made by this new four-element-compound can send out lights ranging from infrared rays to ultraviolet rays.
Some people may ask: how can a Light Emitting Diode send out white rays? In fact, white is a combination of red (21%), green (69%) and blue (10%). However, due to the manufacturing technique, it is impossible for LED spot Lights to emit purely red/green/blue rays. Thus color matching is necessary. Workers need to combine three colors in proportion, and meanwhile control the light intensity of them respectively to create approximate white rays.