LEDRunLights     Made in the USA

LED is a Green energy lighting  The electricity used over the lifetime of a single incandescent bulb costs typical 8 times the original purchase price of the bulb itself. Compact Light Emitting Diode (LED) have revolutionized energy-efficient lighting. LED's are small, solid light bulbs which are extremely energy-efficient, LED last 10 times as long as compact fluorescents bulb, and 120 times longer than typical incandescent bulbs, LED's electricity costs can be reduced by 80% or more because LED's use a fraction of the wattage of incandescent bulbs. Although LED's are expensive, the cost is recouped over time in electricity savings, Electric lighting burns typical up to 25% of the average home energy budget.

How LED function

LED is a diode, LED is a semiconductor chip doped, with impurities to create a p-n junction. The current flows from the p-side, or anode, to the n-side, or cathode, but not in the reverse direction. Charge carriers electrons and holes that flow into the junction from electrodes with different voltages (3 to 3.9VDC). When an electron meets a hole, it falls into a lower energy level, and releases energy in the form of a photon (Photon=light). The wavelength of the light emitted, and therefore its color, depends on the band gap energy of the materials forming the p-n junction. In silicon or germanium diodes, the electrons and holes recombine by a non-radiative transition that produces no optical emission, because these are indirect band gap materials. The materials used for an LED have a direct band gap with energies corresponding to near-infrared, visible or near-ultraviolet light. LED development began with infrared and red devices made with Gallium Arsenide. Advances in materials science have made possible the production of devices with ever-shorter wavelengths, producing light in a variety of colors. LED’s are usually built on an n-type substrate, with an electrode attached to the p-type layer deposited on its surface. P-type substrates, while less common, occur as well. Many commercial LED’s, especially GaN/InGaN, also use sapphire substrate or Silicon carbide Substrates that are transparent to the emitted wavelength, and backed by a reflective layer, increase the LED efficiency. The refractive index of the package material should match the index of the semiconductor, otherwise the produced light gets partially reflected back into the semiconductor, where it may be absorbed and turned into additional heat, thus lowering the efficiency. This type of reflection also occurs at the surface of the package if the LED is coupled to a medium with a different refractive index such as a glass fiber or air. The refractive index of most LED semiconductors is quite high, so in almost all cases the LED is coupled into a much lower-index medium. The large index difference makes the reflection quite substantial and this is usually one of the dominant causes of LED inefficiency. Often more than half of the emitted light is reflected back at the LED-package and package-air interfaces. To minimize the light reflection we using a dome-shaped package with the diode in the center so that the outgoing light rays strike the surface perpendicularly, at which angle the reflection is minimized. An anti-reflection coating may be added as well. The package may be cheap plastic, which may be colored, but this is only for cosmetic reasons or to improve the contrast ratio; the color of the packaging does not substantially affect the color of the light emitted. Other strategies for reducing the impact of the interface reflections include designing the LED to reabsorb and reemit the reflected light (called photon recycling) and manipulating the microscopic structure of the surface to reduce the reflectance, either by introducing random roughness or by creating programmed moth eye surface patterns. Conventional LED’s are made from a variety of inorganic semiconductor materials, producing the following colors for example: The light emitted from using Aluminum gallium arsenide (AlGaAs) is red and infrared. The light emitted from using Aluminum gallium phosphide (AlGaP) is green. The light emitted from using Aluminum gallium indium phosphide (AlGaInP) is high-brightness orange-red, orange, yellow, and green. The light emitted from using Gallium arsenide phosphide (GaAsP) is red, orange-red, orange, and yellow. The light emitted from using Gallium phosphide (GaP) is red, yellow and green. The light emitted from using Gallium nitride (GaN) is green, pure green (or emerald green), and blue also white (if it has an AlGaN Quantum Barrier). The light emitted from using Indium gallium nitride (InGaN) is 450nm - 470nm — near ultraviolet, bluish-green and blue. The light emitted from using Silicon carbide (SiC) as substrate is blue. The light emitted from using Sapphire (Al2O3), as substrate is blue. The light emitted from using Zinc selenide (ZnSe) is blue. The light emitted from using Diamond (C) is ultraviolet.