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Optoelectronics involves converting electrical energy into light and vice versa using semiconductors. Optoelectronic effects include the photoelectric, photovoltaic, electroluminescence, and photoconductivity effects. These effects are used in solar cells, LEDs, copying machines, and other applications. Optoelectronics has revolutionized many industries and is used in products ranging from computers to military equipment.
Optoelectronics is a branch of electronics that deals with converting electrical energy into light and converting light into electrical energy using materials called semiconductors. Semiconductors are crystalline solid materials with electrical conductivities lower than those of metals but higher than those of insulators. Their physical properties can be changed by exposure to different types of light or electricity. In addition to visible light, forms of radiation such as ultraviolet and infrared light that are not visible to the human eye can affect the properties of these materials.
One of the first discoveries in physics that led to the development of modern optoelectronics is known as the photoelectric effect. The photoelectric effect is the emission of electrons from a material when it is exposed to certain types of light. When the material absorbs enough energy in the form of light, the electrons can be knocked off the surface of the material, thus generating an electric current and leaving electron holes behind. A related phenomenon is the photovoltaic effect in which absorbed light causes electrons in a material to change energy states, thus creating a voltage capable of generating electric current.
Generating solar energy from solar cells that absorb sunlight is a common application that takes advantage of these effects. The electricity generated in this way can be used directly or stored in batteries for later use. Practical applications of solar cells include generating power both on land, such as for off-grid homes in remote locations, and in space, such as for satellites.
Electroluminescence is another important effect that is used in optoelectronics. When electricity is applied to certain materials, it drives electrons in high energy states to combine with electron holes and fall into more stable states of lower energy, thus releasing energy in the form of light. Light emitting diodes (LEDs) are a common example of the use of electroluminescence. LEDs in a variety of colors are used as power indicators, in digital displays for items like calculators and appliances, for lighting signs and traffic lights, as headlights and signals on cars, and more. Vehicle dashboards also commonly use electroluminescence for lighting.
Photoconductivity is the phenomenon of the increase in the conductivity of a material under illumination. This effect varies with increased light intensity generating more electrons and electron holes in some materials, thereby increasing the electrical conductivity of these materials. Copying machines were made possible by the application of this particular phenomenon of optoelectronics. When a photoconductive surface in a copier machine is exposed to an image, a difference in conductivity is created between the lighted areas that do not contain the image and the unlighted sections that do. As a result, the powder in the machine is dispensed as an image, after which it is fused onto a piece of paper to complete the copying process.
These and other optoelectronic effects are being integrated into a wide variety of devices and applications in numerous combinations, with even more in development. Many industries have been revolutionized by the application of optoelectronics. Optoelectronic devices play a vital role in applications and products ranging from computers to communications, medical technology to military equipment, photography and other imaging techniques, and beyond.
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