LED'S or light emitting diodes are solid state semiconductor devices that can convert electrical energy directly into light. The heart of a LED is the semiconductor chip of which one side is attached on the top of an anvil; this is the negative power lead. The other side is connected with a whisker to a positive lead. The entire junction is encapsulated in an epoxy type resin enclosure.
A semiconductor chip consists of two parts, one is called P-type semiconductor where holes dominate the region, and the other part is N-type semiconductor where is dominated by electrons. When they are sandwiched together there is a PN junction in between them. When an electric current is applied electrons are pushed across the junction into the P-region. Electrons and holes meet, recombine, and then release energy in the form of photons of light. The wavelength of the light, therefore its colour, depends on the materials forming the PN junction, which are the materials used to make the LED chip.
Generally, LED chips are made from gallium-based crystals that contain one or more additional materials such as phosphor to produce a distinct color.
Development of LED's
Since the first practical visible-spectrum LED was developed in 1962, the development of LED has improved to such a degree, that it has been widely chosen as the best alternative to incandescent bulb, neon and fluorescent lights in many areas. It is predicted that with further development of LED, use of the incandescent bulb, fluorescent and halogen light sources would give way entirely to LED technology largely due to the great power saving and long life characteristics.
The development of LED can be roughly divided into three steps, advent of red light LED, then blue light Led, and white light LED. Red light and green light Led have been developed for decades, but they are all monochromatic LED, if they were used as light sources, objects illuminated would all wear the colour emitted from the monochromatic LED, instead of the inherent color of the objects, so their applications are limited. The ultimate aim of LED development is super-bright white light LED that can eventually replace conventional light sources.
Shuji Nakamura, a Japanese scientist, managed to make a blue light LED from gallium nitride in 1993. It turned out to be a crucial breakthrough in the development of LED's.
Based on the technology of blue light LED, a white light LED was soon invented in 1997. From then on, LED products have been widely used in many lighting applications, and regarded as the light source of future.
- A LED is essentially a tiny chip that encapsulated in an epoxy resin enclosure, so it can be extremely small and light.
- Long lifetime, operating at a desired rated voltage, current and environment, LEDs typically have operating life of up to 80,000 hours.
- High luminous efficiency and Low heat emitting. Due to the special materials that used to make LEDs, during electrons transition, LED's mainly emit electromagnetic energy in the visible parts of spectrum. Unlike the incandescent filaments, which emit a lot of electromagnetic energy in the infrared part of the spectrum which can't be seen but is felt as heat. LEDs can convert almost all of the energy used into light, and therefore, LEDs are of high luminous efficiency and are low heat emitting.
- Unbreakable, the light-emitting device of a LED is completely embedded in an epoxy resin enclosure which is much sturdier than the incandescent bulb, and fluorescent tube.
- There are no loose and moving parts within the solid epoxy enclosure, LED,s are virtually indestructible.
- LED's are made from non-toxic materials, unlike the fluorescent lights with mercury that will pose a pollution hazard. LED,s can also be recycled.
Due to the rich variety in colors, small size, durability, energy savings, LED,s are perfect light source for decorative application. See our products for the Light Effects range of Christmas and decorative LED lights.
With the advance of the white light and warm white LED technology, LED's now provide an effective longer lasting alternative to traditional halogen and incandescent lighting systems.
Monochromaticity is the inherent property of LEDs. They emit a pure color in a narrow frequency range, The color emitted from a LED is identified by peak wavelength (lpk) and measured in nanometers(nm). Peak wavelength is a function of the LED chip material, the composition of the different materials determine the wavelength and therefore the colour of light emitted. See our products for the Light Effects range of mood lighting kits and systems.