Introduction
There are thousands of technological advances in our world that help thousands of people everyday. These technologies range from access to clean water all the way to keeping buildings lit at night. While these technologies are helpful to those that live in a developed country, there are many others around the world that do not have this opportunity. In underdeveloped countries, there are no lamps or lights that can be turned on to continue work inside and outside of the home. This leads to less productivity which could make or break a family. But with Light Emitting Diodes becoming more and more accessible, there is a new type of appropriate technology which could revolutionize the way that countries see light. LED lamps are being created to show countries a new way to look at light.
Defining Solid State Lighting
Solid State lighting is different because instead of using gas or filaments to illuminate, it uses organic light emitting diodes (OLED), Light Emitting Diodes (LED), and also polymer light-emitting diodes (OLED). In solid state lighting, electrons and holes are injected into a forward-biased semiconductor p-n junction; they recombine creating photons; the resulting photons are extracted from the chip; then the photons are either mixed with different-color photons from other LEDs, or are energy down-converted into a distribution of colors using phosphors or other down-conversion materials, with the colors chosen so as to create the appearance of white. The reason for the name solid state simply means that the semiconductor is a block instead of some other device like a gas tube. Unlike traditional lighting, however, SSL creates visible light with reduced heat generation or parasitic energy dissipation. Also, the solid state helps it last longer and makes it a better investment.
Comparing other methods of Light
Flourescent Bulbs
Fluorescent lamps are glass tubes that contain mercury vapor and argon gas. When electricity flows through the tube, it causes the vaporized mercury to give off ultraviolet energy. This energy then strikes phosphors that coat the inside of the lamp, giving off visible light. While these are good sources of light, they are known to have flickering problems from time to time and have to be used properly in order to last long. Another big problem is individuals who are sensitive to light can have health problems from the slight amount of ultraviolet light being given off.
Incandescent Bulbs
Incandescent bulbs work via the element called tungsten, which is the coiled part at the top of the bulb. An electrical current passes through the filament which causes heating until it produces light. while these bulbs are easily reproduced and are cheap, they burn out quicker and use up a lot more energy then they give off.
Calculations Behind LED
The wavelength (and color) of light emitted in a radiative recombination of carriers injected across a p-n junction is determined by the difference in energy between the recombining electron-hole pair of the valence and conduction bands. The approximate energies of the carriers correspond to the upper energy level of the valence band and the lowest energy of the conduction band, due to the tendency of the electrons and holes to equilibrate at these levels. Consequently, the wavelength (l) of an emitted photon is approximated by the following expression:
l = hc/Ebg
where h represents Planck's constant, c is the velocity of light, and E(bg) is the band gap energy. In order to change the wavelength of emitted radiation, the band gap of the semiconducting material utilized to fabricate the LED must be changed. Gallium arsenide is a common diode material, and may be used as an example illustrating the manner in which a semiconductor's band structure can be altered to vary the emission wavelength of the device.[1]